The Sacred Sacred Ibis [reposted]

BY: Bob Montgomerie, Queen’s University | 15 October 2018

Thoth and ibises

The ancient Greeks usually depicted Thoth—their god of writing, wisdom and magic—as having the head of a bird with a long, down-curving bill.  Until the 1800s, Europeans thought that this bird was probably a curlew, a stork or a heron. Linnaeus believed that the bird must be the Cattle Egret which he called Ardea ibis in the 1758 edition of his Systema Naturae. It was not until the turn of the 19th century that a small group of French scientists and naturalists finally confirmed the connection between Thoth and the head of the African Sacred Ibis (Threskiornis aethiopicus). This species was not unambiguously described until 1790 [1], but it took Napoleon Bonaparte’s military campaign to Egypt to provide the connection between this species and Thoth.

We now know that the sacred ibis was considered (and revered) by the Egyptians to be the earthly form of Thoth. For about a millennium starting in 1100 BC, ibises were frequently mummified as an offering to Thoth, believing that mummification would put the birds on a direct line to the afterlife. As a result, several million sacred ibises were killed, gutted, embalmed and folded with the bill tucked between the tail feathers. The carcasses were then wrapped with linen dipped in resin, and inserted individually or in pairs into urns that were placed in vast underground caverns in cities all along the Nile. Many of these mummified ibises have grains, snakes, snails and other foods in their body cavities, possibly to provide the birds with some food in the afterlife.

But why ibises, and where did all of these birds come from? There can be no doubt that the sacred ibis was a reasonably common bird [2] in swampy areas all along the Nile in the Late and Ptolomeic Periods of ancient Egyptian civilization [3]. Those birds were of great value to nearby villages as they ate the snails that infested fish ponds, snails that harboured parasites dangerous to humans. They were also claimed to feed on flying snakes (?) and generally consumed all kinds of human refuse [4]. No wonder they were considered to be sacred.

At several sites of ancient cities along the Nile, archaeologists have found incredible numbers of mummified ibises: 1.75 million at Saqqara, 4 million at Tuna el-Gebel, for example. Even over a period of 500 years that is a lot of birds per year, likely magnitudes more than could have been hunted in the local marshes for any sustained period. Because of their religious importance, sanctuaries dedicated to the ibis sprang up all over the country, where birds were bred and raised in captivity, processing as many as 20,000 ibises per year for the votive ibis industry. Priests apparently gathered eggs for artificial incubation and tended the large flocks, as well as engaging in a large pottery industry to make urns for the mummified birds. These ibiotropheia may well be the earliest examples of bird-farming that did not involve some form of fowl.

The vast stores of ibis mummies in Egypt were brought to light by Geoffery Saint-Hilaire and Jules-César Savigny, two of the 167 savants [5] who accompanied Napoleon Bonaparte to Egypt from 1798-1801. Savigny noticed that the ibis often appeared in hieroglyphics and tomb paintings, and reasoned that this bird was important to Egyptian culture. He wrote up his discoveries in 1805 as Histoire naturelle et mythologique de l’ibis which included some very nice illustrations.

from Savigny (1805) hand-coloured by Louis Bouqet

Georges Cuvier, one of the leading French biologists of the day, was asked by Napoleon to join the Egyptian contingent, but he suggested that Savigny go instead, so he could continue his work on molluscs. But it was Cuvier who first measured two mummified birds brought back from Egypt by Col. Jacques François-Louis Grobert [6] from the catacombs at Saqqara.  Cuvier initially concluded that those birds were probably curlews as they were smaller than some contemporary ibis specimens [7]. He later measured two mummies that Geoffrey Saint-Hilaire had brought home from Thebes. Those measurements plus the colours of some intact feathers convinced him that the mummies collected by Saint-Hilaire were indeed sacred ibises, and his 1804 paper has a very nice summary of his reasoning and all of the previous mis-identifications. Cuvier’s assistant even pieced together the bones from different mummies to make a complete skeleton (see picture below).

Even though the ibis mummies from Saint-Hilaire were not exactly the same size as contemporary birds, Cuvier also used those measurements to bolster his arguments of the fixity of species—evidence that species were created once by a deity and did not change through time. This argument put him at odds with his colleague Lamarck who argued that species changed through geological time.

I was made aware of this ibis story in a new essay in PLoS Biology [8], by Caitlin Curtis, Craig Millar and David Lambert. As Jerry Coyne noted in an essay on his Why Evolution is True site, not many evolutionary biologists seem to be aware of this as an early test of evolutionary change. The reason, I think, is that it was not actually a test [9]. The story is actually rather well known and has been published many times in scientific journals and the popular press ever since Cuvier’s initial publications [10]. While the new essay summarizes many aspects of this story the authors present no evidence in support of some of their claims and I am not entirely convinced by some of their assertions.

Cuvier (1804) identifies the mummies as sacred ibises

When interpreting the past here is always a danger of applying present knowledge and values incorrectly. In this case, I cannot yet tell if my different interpretation of this interesting story is correct. I will need to read the work of Cuvier, Lamarck, Saint-Hilaire and Savigny in the original French and Latin to put the whole story in context but that will take a while, even though all of the relevant texts are now available online. I will revisit the topic when I have done the necessary research.

Whether the details in this new essay by Curtis and colleagues are correctly interpreted or not, it does end with a curious conclusion that I feel deserves some further discussion: Of great importance is the reminder, even today, of the power of a strong personality and that the belief in “what they know to be true” can dramatically influence the direction of science and public opinion. I do not think that anyone would dispute that strong personalities and beliefs can influence science and public opinion. Take, for example, Julian Huxley’s rejection of Darwin’s ideas on sexual selection [11], undoubtedly reducing interest in that topic for the next 50 years or so.  And while it is true that Huxley and Cuvier had strong personalities, and were great communicators and relatively powerful men, I think that their arguments held sway largely because they made them clearly and because there was neither compelling evidence nor any clear and logical mechanisms to explain the existing patterns. In both cases the delays in the progress of science were reasonably short and probably needed the ideas and considerable evidence presented by Darwin and Wallace, and Williams and Trivers, respectively, before there could be any real progress.

Finally, it has probably not escaped your notice that the African Sacred Ibis has been depicted on the cover of The Ibis in one form or another ever since 1859. This may seem a bit odd as that bird does not occur in the wild in Britain and only sparsely in southern Europe through introductions. Thus the sacred ibis does not really appear to be a fitting symbol for the British Ornithologists’ Union. There is a long and interesting story there, but that too will have to wait for another day.


  • Birkhead TR, Wimpenny J, Montgomerie R (2014) Ten Thousand Birds: Ornithology since Darwin. Princeton, NJ: Princeton University Press.
  • Cuvier G (1804) Mémoire sur l’ibis des anciens Égyptiens. Annales du Muséum d’histoire naturelle 4:116-135. [available here]
  • Cuvier G (1812) Recherches sur les Ossemens Fossiles de Quadrupèdes : où l’on rétablit les caractères de plusieurs espèces d’animaux que les révolutions du globe paroissent avoir détruites, t1-4. [Studies of the Fossil Bones of Quadrupeds, volumes 1-4] Paris: Deterville. [available here]
  • Cuvier G (1826) Discours sur les révolutions de la surface du globe, et sur les changemens qu’elles ont produits dans le régne animal. Paris: G. Dufour. [available here and in English translation of the 1825 edition here]
  • Lacépède B-G-E, Cuvier G, Lamarck J-B (1802) Rapport des professeurs du Muséum sur les collections d’histoire naturelle rapportées d’Égypte, par E. Geoffrey. Annales du Museum d’Histoire Naturelle 1: 234–241. [available here]
  • Latham J (1790). Index Ornithologicus, Sive Systema Ornithologiae: Complectens Avium Divisionem In Classes, Ordines, Genera, Species, Ipsarumque Varietates (2 Volumes, in Latin). London: Leigh & Sotheby. [available here]
  • Le-Suer RB, ed (2012) Between Heaven and Earth: Birds in Ancient Egypt. Chicago: The Oriental Institute of the University of Chicago
  • Linnæus  C (1758) Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis, 10th edition.  Stockholm: Laurentius Salvius.
  • Rosser WH (1837) Mummy of Egyptian Ibis. The Gentleman’s Magazine 6 (new series): 145-148. [available here]
  • Savigny J-C (1805) Histoire naturelle et mythologique de l’ibis [Natural and Mythological History of the Ibis]. Paris: Allais. [available here]


  1. ibis described: see Latham 1790 page 706 where he calls it Tantalus aethyopius
  2. Sacred ibis once common in Egypt: but it is no longer found in that country, disappearing as the swamps and marshes were drained to provide land for the increasing population and agriculture.
  3. Late and Ptolomeic Periods: about 700 BC until 30 BC ending with the death of Cleopatra and the conquest of Egypt by the Romans
  4. ibises eating refuse: in Australia, where they have been introduced, they are often called ‘bin chickens’ as they are often seen foraging in trash cans in city parks. In the park beside the Australian National Museum in Sydney, I once watched a very dirty-looking ibis sneak up behind some picnickers then reach over the shoulder of a little boy to snatch his sandwich out of his hand. Clearly, their bills are adapted for sandwich snatching (!), and they are fearless.
  5. savants: these were scholars and scientists. The Journal des Sçavants (later called Journal des Savants) began publishing in January 1665, a couple of months before the Philosophical Transacations of the Royal Society, considered (erroneously) by many to be the first scientific journal. Frankly, I don’t see that it matters who was first, or even if it was one of those two.
  6. Grobert: (1757-181?) was a French artillery officer who wrote about the pyramids etc. on his return from the Egyptian campaign. See Cuvier (1826), which updates some of the information in his 1804 publication about his later study of some different mummies.
  7. smaller than contemporary ibises: On examining four more ibis mummies, Cuvier recognized that one of them was a juvenile based on its bone structure (Cuvier 1826). As a result, he realized that they may not be curlews at all but simply smaller, juvenile ibises. This is not so surprising as it turns out the many of the ibis mummies were clearly made from juvenile birds. No doubt the priest-farmers who raised the ibises for the votive market saw no reason to keep the birds any longer than was needed to make them suitable for mummification.  That just made good economic sense to maximize their profits.
  8. article in PLoS Biology: unlike the scientific articles in that journal, this one is labelled ‘Essay’ which they say “are opinionated articles on a topic of interest to scientists, as well as to a broader audience, including the general public”. Opinions are fine but I am surprised at the absence of clear evidence in support of the claims made.
  9. not actually a test: Cuvier simply used his measurements identifying the mummies as sacred ibises to suggest that there had not been much change in their morphology in the past 3000 years. But the ibis was just one of many examples that he referred to. Moreover, as Coyne noted, this was at best a ‘one-way test’ as any lack of change would be consistent with slow evolutionary change. Cuvier even acknowledged that the the measurements were not the same between the mummies and contemporary ibises. I don’t see this as a test of any kind because Cuvier was unlikely to be convinced by any such results: if the mummies were the same as extant ibises, then no change; if they were different then they must be different species.
  10. the story of Cuvier’s ibis measurements: in a quick search on the internet, I found more than 20 articles on Cuvier’s ibis measurements dating back to Rosser (1837)
  11. Huxley and sexual selection: see Birkhead et al. (2014)

NOTE As some of you may have noticed, this essay was briefly posted by accident in draft from a week ago. I immediately deleted that version from this blog and the final version above is substantially different, correcting several errors in the original and providing additional information, references and links.

Much Ado About a Cockatoo (reposted)

BY: Bob Montgomerie, Queen’s University | 2 July 2018

For the past week or so the internet has been abuzz about a cockatoo depicted 4 times in the margins of Frederick II’s De Arte Venandi cum Avibus written around 1245 CE [1]. The story is that this bird suggests a mediaeval trade route from Australia to Italy, overturning the Eurocentric notion that Australia was a dark continent until ‘discovery’ by Dutch sailors early in the 17th century. This story has already been retweeted about 2000 times on Twitter, and has appeared in the popular press worldwide, including CNN, Reuters, ABC (Australia), Japan Times, and The Guardian [2].

Marginal cockatoos (numbers indicate folio pages)

This story began with an original paper published last month  in the journal Parergon [3] by Heather Dalton, Jukka Salo, Pekka Niemelä and Simo Örmä. That paper is wonderfully detailed about the creation and provenance of De Arte, about the source of Frederick’s cockatoo, and the details of the four coloured drawings of the cockatoo in the surviving copy of the original manuscript housed in the Vatican Library in Rome [4]. The popular press has been remarkably accurate in reporting the details of that paper, avoiding the hyperbole and small misleading errors that too often characterize science journalism.

Here, in a nutshell, are 5 quotes that summarize what I think are the important features of this story:

  1. Frederick_II_and_eagle
    Frederick II

    “Frederick II of Sicily made contact with the Kurdish al-Malik Muhammad al-Kamil in 1217… The two rulers communicated regularly over the following twenty years, exchanging letters, books and rare and exotic animals….[like] the Sulphur-crested or Yellow-crested Cockatoo the sultan sent Frederick.”  [5]

  2. “De arte was written in Latin by Frederick or a scribe under his direction between 1241 and 1244…Amongst the nine hundred marginal illustrations of birds, animals, falconers, perches, and falconry equipment are four coloured drawings of the white cockatoo gifted to Frederick II.” [5]
  3. “Discovery of earliest European depiction of cockatoo in medieval book rewrites history of global trade” [6] see also quote 7
  4. “Because the four images in the Vatican manuscript have rarely been reproduced in print, few people are aware of their existence. This may be because many scholars have relied on Casey Albert Wood and Florence Marjorie Fyfe’s 1943 English translation of all six books of the De arte. 11 Although Wood and Fyfe included many illustrations from the Codex Ms. Pal. Lat. 1071, they did not include those of the cockatoo. [5]
  5. “Bearing in mind the shape of the crest, the blue/grey of the periophthalmic ring and the lack of a yellow tinged ear patch, Frederick’s cockatoo was in all likelihood a Triton Cockatoo…or one of the three subspecies of Yellow-crested Cockatoos that have a yellow crest.” [5]
  6. “The main significance about it is we tend to think of our region, not just Australia, but the islands around it, as the very last things to be discovered; the European view is it’s almost this dead continent and nothing was happening until Europeans discovered it.” [7]

While Dalton and colleagues have done a great job summarizing all of the details in their paper, I do have a few quibbles with the final four points listed above. I was, for example, a little surprised to hear of the ‘discovery’ of these cockatoo drawings because I certainly knew about them. As so often happens, I wondered if I had simply failed to realize their significance.

But as the paper so nicely summarizes, previous authors [8] had written about the cockatoos, so this new work might be better characterized as a re-discovery. In fairness, Dalton and colleagues never claimed this to be a new discovery but this is the way that most of the popular press has characterized their work.

Wood and Fyfe p 38: cockatoo is at top of right margin

They do claim (point 4), however, that modern scholars are generally unaware of these illustrations, largely because everyone reads Wood and Fyfe’s translation from 1943. But that’s how I knew about the cockatoo—one of the pages (folio 18v) with the cockatoo in the margin is reproduced, albeit in black and white, on page 38 in Wood and Fyfe’s book. In the caption they even say  “also containing the reference to the parrot (?) sent to Frederick by the Sultan of Babylon”, and in a footnote on page 59 they say it was likely a cockatoo from the Sunda Islands.

Dalton and colleagues do a really nice job of describing the four coloured marginal drawings and they use those details to try to identify the bird. They make the reasonable conclusion that it was likely a female Sulphur- or Yellow-crested Cockatoo. Others have suggested that it might be a White Cockatoo [8]. Nonetheless, I cannot agree with the authors’ assumption that those descriptions are very useful for identification.


For example, in the De Arte illustrations, it looks like the birds have yellowish flanks and back, whereas none of the potential cockatoos have that colouring [9]. They also interpret the shape of the crest as ruling out the White Cockatoo, but the shape and size of the bill, feet, and wing feathers are so inaccurate that I would not be inclined to assume that the crest is correctly drawn. Moreover, none of the illustrations in De Arte show the characteristic yellow cheek patch of the Yellow- and Sulphur-crested.

peacockFiiThe marginal drawings are, after all, crude by modern standards, as you can see from the reproductions above. The manuscript has at least 7 marginal drawings of peacocks [10], for example, that show that, although the artist was remarkably good for his day, he was no Lars Jonsson. Thus it would be entirely reasonable for Frederick’s bird to be a White or Yellow-crested Cockatoo, from Sulawesi (one of the Sunda Islands) or the Moluccas [11]. If that is correct then I am not so sure that this cockatoo really tells us anything about mediaeval trade routes.

It has long been known that there was extensive trade between southeast Asia and the Middle East along the Silk Road, beginning centuries before Frederick’s day. That ‘road’ includes several marine routes extending as far east as Sulawesi and the Sunda Islands (see map below). While there may have been some trade between New Guinea and northern Australia in the 13th century, there is really no evidence for this, as far as I know. Thus, Australia does seem to have been a relatively ‘dark continent’ until the 17th century, especially to Europeans, and Frederick’s cockatoo does not really shed any light on that narrative.

I feel that I should emphasize how much I enjoyed the original article by Dalton and colleagues, despite my reservations above. In my view, science progresses when there is some healthy skepticism, and that’s what I have tried to present here.

Land and marine trade routes in mediaeval times.

NOTE: I accidentally posted an incomplete version of this essay a couple of days ago. My apologies for that. I blame the heat.


  • Dalton H, Salo J, Niemelä P, Örmä S (2018) Frederick II of Hohenstaufen’s Australasian Cockatoo: Symbol of Detente between East and West and Evidence of the Ayyubids’ Global Reach. Parergon 35: 35-60.

  • Frederick II (~1245) De arte venandi cum avibus. Vatican City, Biblioteca Apostolica Vaticana, codex Ms. Pal. Lat. 1071.
  • Kinzelbach R (2008) Modi auium – Die Vogelarten im Falkenbuch des Kaisers Friedrich II’. pp 62–135 in Vol 2 of Kaisers Friedrich II 1194–1250: Welt und Kultur des Mittelmeerraums (ed. Ermete K, Mamoun Fansa M, and Carsten Ritzau C). Mainz: Philipp von Zabern.
  • Rowley, I. (2018). Cockatoos (Cacatuidae). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from on 2 July 2018).
  • Stresemann E (1975) Ornithology from Aristotle to the present. Cambridge, MA: Harvard University Press.

  • Willemsen CA (1980) Das Falkenbuch Kaiser Friedrichs II. Nach der Prachthandschrift in der Vatikanischen Bibliothek. Dortmund: Harenberg.

  • Wood CA, Fyfe FM (1943) The Art of Falconry; Being the De Arte Venandi cum Avibus of Frederick II of Hohenstaufen by Frederick the Second of Hohenstaufen. Stanford: Stanford University Press.

  • Yapp WB (1983) The illustrations of birds in the Vatican manuscript of De arte venandi cum avibus of Frederick II. Annals of Science 40: 597–634


  1. Frederick II’s manuscript: see my earlier post on this ornithologically important masterpiece here
  2. articles in popular press: but curiously not (yet) The New York Times or any of the other leading American and Canadian news media outlets.
  3. Parergon: is the journal of the Australian and New Zealand Association of Medieval and Early Modern Studies (Inc.), and has been publishing refereed articles since 1983.
  4. Frederick’s manuscript in the Vatican Library: is also available for study online in two spectacularly reproduced digital copies here and here.
  5. Quotations 1, 2, 4 & 5: from Dalton et al. 2018
  6. Quotation 3: from the headline in The Telegraph (UK)
  7. Quotation 6: Helen Dalton quoted in The Guardian (UK)
  8. previous authors on this cockatoo: see, for example, Wood and Fyfe (1943), Stresemann (1975), Willemsen (1980), Yapp (1983), Kinzelbach (2008)
  9. yellowish back and flanks: I would be inclined to interpret this colour as shading rather than as the colour of the feathers.
  10. peacocks: would probably have been a very familiar bird in the courtyards of Italy in the 13th century, having been traded along the Silk Road for centuries before. Like the cockatoo, those drawings would have been based on live speciemens
  11. likely species: Dalton et al. (2018) do seem to favour the Yellow-crested Cockatoo in their analysis, so it is curious to me that they make such a fuss about the trade routes, since the range of the Yellow-crested on one of those mediaeval routes

IMAGES: Cockatoos and peacocks from De Arte copied from the online versions; Frederick II and Silk Road map from Wikipedia; Cockatoos and range map from Handbook of Birds of the World (Rowley 2018); page from Wood and Fyfe scanned from the author’s copy.

Why Woodpeckers are Scarce in the North

BY: Bob Montgomerie, Queen’s University | 18 June 2018

On the 18th of June 1858, one hundred and sixty years ago today, Darwin claims [1] to have received that fateful letter from Alfred Russel Wallace—probably the most famous letter in the history of science. The original letter was lost but it was transcribed and read to the Linnean Society of London on 1 July and published later in their journal. That letter is well worth reading, especially because it contains some interesting insights into avian ecology. While Wallace had some useful ideas relevant to natural selection, it could be argued that his argument was not nearly as well-formed as Darwin’s [2]. In a way, his ecological and biogeographical insights are more original, in my opinion.

Wallace in 1862

Wallace wrote that letter on Ternate in the Mollucas in February 1858, sent it out on a mail steamer on 5 April. He was in the South Pacific for 8 years on a collecting trip, in part to obtain specimens that he could sell back in England but also to gather material for books that he thought, rightly so, would provide him with a lifetime of fame and fortune. He brought home more than 125,000 specimens, including more than 8000 bird skins.


I found three things to be remarkable about Wallace’s letter. First, he develops some of the same ideas about selection as Darwin,  and uses some of the same language: “state of nature”, “struggle for existence”, “stability of species”, “geometrical ratio”, “origin of…species”,  “conditions of existence”, and “superior varieties.” These are not phrases you would be likely to read in a recent paper on evolutionary biology, but may well have been argots of the scientific literature in the 1800s.

Second, he makes clear his objections to Lamarck’s ideas:

The hypothesis of Lamarck—that progressive changes in species have been produced by the attempts of animals to increase the development of their own organs, and thus modify their structure and habits—has been repeatedly and easily refuted…the view here developed renders such an hypothesis quite unnecessary, by showing that similar results must be produced by the action of principles constantly at work in nature. [3]

And third, he is remarkably insightful and creative about what today we would call evolutionary ecology with respect to passenger pigeons, woodpeckers, and clutch size.

On clutch size, he makes the perceptive observation that a species’ population size—and rate of increase—has nothing to do with the number of offspring in a brood:

…large broods are superfluous. On the average all above one become food for hawks and kites, wild cats and weasels, or perish of cold and hunger as winter comes on. This is strikingly proved by the case of particular species; for we find that their abundance in individuals bears no relation whatever to their fertility in producing offspring. Perhaps the most remarkable instance of an immense bird population is that of the passenger pigeon of the United States, which lays only one, or at most two eggs, and is said to rear generally but one young one. [3]

Great Spotted Woodpecker

On woodpeckers, he argues that they are more scarce in the temperate zone than in the tropics due to the uncertainty of overwinter food in the north, and the various morphological adaptations that would make long-distance migration difficult. I don’t even know if these observations are true, but the idea is immensely creative and demonstrates his excellent ecological insights:


Those whose organization does not permit them to migrate when their food becomes periodically scarce, can never attain a large population. This is probably the reason why woodpeckers are scarce with us, while in the tropics they are among the most abundant of solitary birds. Thus the house sparrow is more abundant than the redbreast, because its food is more constant and plentiful,- seeds of grasses being preserved during the winter, and our farm-yards and stubble-fields furnishing an almost inexhaustible supply. [3]

On the Passenger Pigeon, he reasons—correctly, I think—that its unbelievably huge populations were a product of the bird’s ability to move efficiently to track the vagaries of its occasionally superabundant food supply:

Perhaps the most remarkable instance of an immense bird population is that of the passenger pigeon of the United States, which lays only one, or at most two eggs, and is said to rear generally but one young one. Why is this bird so extraordinarily abundant, while others producing two or three times as many young are much less plentiful? The explanation is not difficult. The food most congenial to this species, and on which it thrives best, is abundantly distributed over a very extensive region, offering such difference of soil and climate, that in one part or another of the area the supply never fails. The bird is capable of a very rapid and long-continued flight, so that it can pass without fatigue over the whole of the district it inhabits, and as soon as the supply of food begins to fail in one place is able to discover a fresh feeding-ground. [3]

Like his contemporaries, however, Wallace reasoned that this species’ populations were just too big to fail: “This example strikingly shows us that the procuring a constant supply of wholesome food is almost the sole condition requisite for ensuring the rapid increase of a given species, since neither the limited fecundity, nor the unrestrained attacks of birds of prey and of man are here sufficient to check it. In no other birds are these peculiar circumstances so strikingly combined.” [3] This is one of those rare cases where we could actually learn from history and maybe not repeat Wallace’s mistake in our dealings with other species.


  • Bock WJ (2009) The Darwin-Wallace myth of 1858. Proceedings of the Zoological Society 62:1–12.

  • Davies R (2008) The Darwin conspiracy: origins of a scientific crime. London: Golden Square Books
  • Davies R (2012) How Charles Darwin received Wallace’s Ternate paper 15 days earlier than he claimed: a comment on van Wyhe and Rookmaaker (2012). Biological Journal of the Linnean Society 105:472–477.

  • Darwin CR, Wallace AR (1858) On the tendency of species to form varieties; and on the perpetuation of varieties and species by natural means of selection. Journal of the Proceedings of the Linnean Society of London, Zoology 3:46–50.

  • Davies R (2012) How Charles Darwin received Wallace’s Ternate paper 15 days earlier than he claimed: a comment on van Wyhe and Rookmaaker (2012). Biological Journal of the Linnean Society 105:472–477.

  • Gould E, Gould J, Lear E (1837) The Birds of Europe. (v. 1-5). London: pub. by the author.
  • Smith CH (2013) A further look at the 1858 Wallace–Darwin mail delivery question. Biological Journal of the Linnean Society 108:715–718.


  1.  Darwin’s claim about Wallace’s letter: Davies (2008) in particular, claimed that Darwin received the letter earlier and plagiarized it in his own notes so that he could claim priority, This seems highly unlikely to me, based on what I know of Darwin’s character and what Darwin himself says about the letter. van why and Rookmaaker (2012) present a convincing counter argument (but also see Davies 2012)
  2. Wallace’s ideas on natural selection: see Bock (2008) for details on what Wallace did have to say about selection
  3. Quotations: are all from the transcribed version of Wallace’s letter, available here

Audubon’s Legendary Experiments

BY: Bob Montgomerie, Queen’s University | 11 June 2018

In his Ornithological Biography [1], John James Audubon describes two experiments that have become legends in the annals of ornithology. Both were ingenious ideas, but Audubon’s conclusions were misleading and remained uncorrected for more than a century. According to  a new paper by Matthew Halley in Archives of Natural History, one of those experiments might never have been conducted at all.

mill grove
Audubon mansion at Mill Grove

In the spring of 1804, just before his 19th birthday [2], Audubon found an Eastern Phoebe nest in a cave near where he was living, at the plantation his father had purchased at Mill Grove, Pennsylvania [3]. Audubon had arrived from France a few months earlier and immediately began exploring the countryside where, he said “Hunting, fishing, drawing, and music occupied my every moment; cares I knew not, and cared naught about them. I purchased excellent and beautiful horses, visited all such neighbors as I found congenial spirits, and was as happy as happy could be.” [4]

Audubon wondered whether his phoebes might exhibit what we would now call ‘natal philopatry’: “I had at that period an idea that the whole of these birds were descended from the same stock.” [5]. To test that idea, he put some ‘light threads’ on the legs of the 5 nestlings. The birds, or their parents, repeatedly removed those threads but finally gave up [6]. Once the birds had habituated to the threads, Audubon says that “when they were about to leave the nest, I fixed a light silver thread to the leg of each, loose enough not to hurt the part, but so fastened that no exertions of theirs could remove it.” [7]. Others have, I think, misinterpreted Audubon’s ‘silver thread’ as being silver-coloured yarn but the term is (and was) also used for wire made of silver. Audubon later refers to these as ‘rings’ (see below) suggesting that they were solid and unlikely to be removable by the birds.


The next year, Audubon claims, he found two of those marked phoebes—which he called pewees—nesting near where they were born:

…I had ample proof afterwards that the brood of young Pewees, raised in the cave, returned the following spring, and established themselves farther up on the creek…At the season when the Pewee returns to Pennsylvania, I had the satisfaction to observe those of the cave in and about it. There again, in the very same nest, two broods were raised. I found several Pewees nests at some distance up the creek, particularly under a bridge, and several others in the adjoining meadows, attached to the inner part of sheds erected for the protection of hay and grain. Having caught several of these birds on the nest, I had the pleasure of finding that two of them had the little ring on the leg.” [8]

Now Halley—correctly I think—calls into question the veracity of these observations of natal philopatry, First, he points out, the 40% return rate (2 of 5 banded) of Audubon’s nestling phoebes far exceeds the rate of natal philopatry for this species—and indeed all passerine birds [9]—revealed in subsequent research with large sample sizes. Work done from 1988-90 at my own institution’s field station by Kelvin Conrad, for example, showed a 1.3% return rate of 217 banded nestlings [10]. A much larger study in Indiana [11] found that only 218 of 11,847 (1.8%) phoebe nestlings returned to anywhere within a 250-kmstudy area. Based on those numbers, the chance that 2 of Audubon’s 5 nestlings actually returned is almost zero.

Second, Halley checked the dates of Audubon’s return to France (12 March 1805) and subsequent arrival back in Mill Grove (4 June 1806). Based on the normal first egg dates from nearby sites, Halley argues that Audubon could not have been at Mill Grove during the 1805 breeding season and could therefore not have observed the returns he claimed. While I think Halley is correct, it is always possible that Audubon was mistaken about the years when he conducted this experiment.

My guess, though, is that Audubon did actually make up this story, not about banding the birds [12] but about them returning to their natal site. Audubon was well known to be desperate to establish his reputation as an ornithologist, in part, at least, to enhance the sales of his fabulous collection of etchings based on his paintings of North American birds. Audubon was often at odds with Alexander Wilson and George Ord, sometimes plagiarizing Wilson and fabricating evidence so that he would be seen as the first to record a species of bird or an interesting observation [13]. Elliott Coues, for example, said that Audubon: “..loved warmth, color, action; he liked to exaggerate and ’embroider,’ and make his page glow like a hummingbird’s throat, or like on of his many marvellous pictures; he had no genius for accuracy, no taste for dull, dry detail, no care for a specimen after he had drawn it.” [14]

Audubon’s other misleading experiment was designed to assess the ability of Black Vultures to detect odours, but that is a story for another day. Whether or not Audubon was always accurate in his descriptions of bird behaviour or his timelines of events, his experiments were certainly ingenious. He probably does deserve credit as the first person to band birds in North America, and he really could paint a marvellous picture:

Audubon’s Black Vultures


  • Audubon JJ (1831-1839) Ornithological biography : or an account of the habits of the birds of the United States of America; accompanied by descriptions of the objects represented in the work entitled The Birds of America, and interspersed with delineations of American scenery and manners.  5 volumes. Edinburgh: Adam & Charles Black

  • Audubon JJ (1827-1838) The Birds of America. Edinburgh & London: J. J. Audubon.

  • Audubon MR (1897) Audubon and His Journals, with Zoological and Other Notes by Elliott Coues, vol. 1. New York: Charles Scribner’s Sons.

  • Burns FL (1908) Alexander Wilson: II. The Mystery of the Small-Headed Flycatcher. The Wilson Bulletin 20:63–79.

  • Halley MR (2018) Audubon’s famous banding experiment: fact or fiction. Archives of natural history 45:118–121.

  • Weatherhead PJ, Forbes MRL (1994) Natal philopatry and the cost of dispersal in Passerine birds. Behavioural Ecology 5:426–433.

  • Weeks Jr HP (2011) Eastern Phoebe (Sayornis phoebe), version 2.0. In The Birds of North America (A. F. Poole, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA.


  1. Ornithological Biography: designed by Audubon, with the help of William MacGillivray, to accompany his paintings in Birds of North America. This 5-volume treatise (available here) contains many interesting details and insights about birds but is not an easy read.
  2. 19th birthday: Audubon was born on 26 April 1785 in the French colony that is now Haiti
  3. Audubon’s home: Audubon travelled from France to Mill Grove by himself, on the orders of his father to manage the plantation but was more interested in natural history and he eventually drove the plantation into bankruptcy
  4. quotation about hunting etc: from Audubon 1897, page ; one of the neighbours he talks about was William Blakewell, father of the woman he married a couple of years later
  5. quotation about phoebe philopatry: from Audubon (1831-39) vol 2, 1834, page 125
  6. phoebes removing threads: this thread removal and habituation must have occurred over less than two weeks as phoebes leave the nest after 16-18 days
  7. quotation about silver threads: from Audubon (1831-39) vol 2, 1834, page 125
  8. quotation about returning phoebes: from Audubon (1831-39) vol 2, 1834, page 125-127
  9. natal philopatry of passerines: Weatherhead and Forbes (1994) summarized the rates of natal philopatry for 32 migratory passerines from various published and unpublished studies. The highest recorded rate of natal philopatry was 13.5%, and the majority of species had rates <5%, much lower than Audubon recorded for his phoebes
  10. natal philopatry in Ontario: unpublished data summarized in Weatherhead and Forbes (1994)
  11. natal philopatry in Indiana: unpublished data summarized in Weeks (2011)
  12. Audubon banding birds: I am inclined to believe that Audubon did band those birds as the details ring true. He thus deserves his reputation as America’s first bander, preceding by almost a century the next attempt to band birds in the America’s
  13. Audubon’s conflicts and plagiarism: see Halley (2018) for a brief summary
  14. Elliott Coues quotation: as quoted by Burns 1908 page 68

IMAGES: Audubon mansion from Audubon (1897);  Audubon’s paintings from his Birds of America (1827-38)

Callow Youth

BY: Bob Montgomerie, Queen’s University | 11 December 2017

In science, controversies often arise over complex issues when researchers approach a problem from different points of view, backgrounds, and philosophies—think, for example, of the debates over nature vs nurture, selection vs drift, group vs kin vs individual selection, gradualism vs punctuated equilibria, and mechanisms of sexual selection. As Ledyard Stebbins pointed out in 1982, the resolution of these controversies often settles somewhere in the middle because, in fact, both sides were correct to some extent [1]. Usually scientific controversies churn away towards some resolution with some degree of civility, at least in public forums. But not always…

I can still remember my first experience with a less-than-polite public argument among ornithologists. This occurred during a talk at an AOU meeting in the 1970s when two prominent systematists got into a shouting match during the question period after a graduate student’s talk. The issue was whether the approach taken by the student was correct, and the argument seemed to be between the cladists and the pheneticists.

I learned later that these clashes among systematists were commonplace in the 1960s and early 70s, during a period that was later referred to as the ‘Systematics Wars’ [2]. I was doubly surprised at such ad hominem attacks because the systematists that I knew from my years as a young volunteer and employee at the Royal Ontario Museum—L.L. Snyder, Jim Baillie, Jon Barlow, Jim Rising, and Allan Baker—seemed like the kindest of men. My own field of behavioural ecology, while often dealing in controversy, does not seem to have descended into the sort of personal attacks that characterized those arguments about systematics in the mid 1900s.

While scouring some older literature, we recently discovered [3] that the ‘Systematics Wars’ period was not the first time that avian systematists had engaged in rather nasty exchanges. During the 1830s, for example, two young  brothers—Charles Thorold Wood and Neville Wood, tried to change the rules about naming birds in a way that involved heated debate, vitriol, and ad hominem attacks in their publications.

The Wood boys were wealthy, aristocratic, well-educated, and precocious. In 1835, when he was only 18, Charles published a quirky book—The Ornithological Guide—comprising 236 pages of poetry about birds, a compendium of ornithological books, each briefly reviewed, and a catalog (list) of the birds of Britain. Not to be outdone by his older brother, Neville published two books the next year, when he turned 18—British Song Birds and Ornithologists’ Text-book. British Song Birds alone ran to 400 pages, and, though it appeared not to include any novel observations, summarized much of what was then known about each species. Notably, none of the Woods’ publications included any illustrations.

The Woods felt that the names of birds—both scientific and English—were in a chaotic state and needed rules to make them more ‘scientific’. They were right. Even though Linnaeus had proposed his binomial system almost a century earlier [4], rules for zoological nomenclature that would provide some consistent structure and process were just beginning to be proposed in the 1830s [5].

Female and male European Bullfinches, by John Gould 1837 in his Birds of Europe

The English names were more confusing and disorganized. In England, some birds were even given different English names in different parts of the country. In the 1800s, for example the European Bullfinch was variously called: Bull Flinch (Yorks), Bull Head, Bulldog, Bull Spink, Bully (Yorks), Thick Bill (Lancs), Alpe, Hoop, Hope (SW), Tope, Hoof, Cock Hoop (Hereford), Olf (E Suffolk), Nope (Staffs/Shrops), Mwope (Dorset), Mawp (Lancs), Pope (Dorset), Red Hoop (m, Dorset), Blood Olp (m, Surrey/Norfolk), Tawny (f, Somerset), Tony Hoop, Tonnihood (f, Somerset), Black Cap (Lincs), Billy Black Cap, Black Nob (Shrops), Monk, Bud Bird, Bud Finch, Bud Picker (Devon), Budding Bird (Hereford), Plum Bird, and Lum Budder (Shrops) [6].

The Woods were sure that some logic and rules for the structure of English names were needed if ornithology was to develop as a science. As Neville said in one paper ”“If the proper English generic names were applied to every bird, how greatly would the acquisition of this fascinating study be facilitated! . . . By using the names which I have given above, this [confusion] is remedied, and all becomes plain and easy to understand.” [7] Their solution, for English names, was to make every bird within a genus have the same ’surname’, just as every genus had the same first name in the Linnaean system of Latin names. Thus, for example, Neville proposed:


It was also suggested  at the time [8] that English names be cleansed of modifiers that indicate size, abundance, location, or honorific. Thus present-day names like Little Cuckoo, Common Cuckoo, Moluccan Cuckoo, and Klaas’s Cuckoo would all have to be changed in the Cuculidae alone. Fortunately, cooler heads prevailed, as Hugh Strickland argued that common names were “consecrated by usage as much as any other part of the English language”. As he noted “the science of ornithology does not suffer by this incorrect application of English names, because those familiar appellations have no real or necessary connection with science”. Despite his admonition, the English names of birds are still in a state of flux today and may always be.

The Woods’ proposals were well reasoned, if sometimes seeming to be a little bizarre today. But their suggestions were often presented in such a way that demeaned those who had different points of view. In the Preface to his Bird Song Birds, Neville says: “while I agree with my predecessors in many points, I have found much to correct, and still more to add, to the meagre and unsatisfactory accounts of most of our British Ornithologists.” Ouch!

Neville’s review of Eleazar Albin’s Natural History of Birds claimed that it was “of no use in the present day” and of Jennings Ornithologia that he ”never had the misfortune to meet with a book so full of errors . . . We should have considered such a work beneath our notice, as it is impossible it can have the smallest connection with the advancement of Ornithology”. [9] Their writings are sprinkled with derogatory epithets and harsh criticism that even today strikes me as ungentlemanly, possibly simply the result of the Woods being callow youth [10].

Possibly because they gained few converts, and appear not have been well liked, both Charles and Neville drifted off to other pursuits before their 35th birthdays, never again to write about birds or to heap opprobrium on their fellow ornithologists. Charles published his last paper on birds (again on nomenclature) when he was 19 and then seems to have vanished from the public record; Neville trained as a doctor, and at the age of 26 moved to London where he practiced the new medical system called ‘homeopathy’ for the rest of his life. At least if he had stayed with birds he would have done something potentially useful.

Stebbins ended his 1982 address to the American Association for the Advancement of Science [11] by saying that: “My final hope is that evolutionists having different backgrounds and viewpoints will reduce their rivalry and collaborate increasingly in zealous research toward finding answers to these and other questions of major significance.” This was a noble sentiment but ignored those ineluctable human (or at least male) foibles of ego, ambition, and competitiveness. I would argue that controversies are are valuable part of scientific progress, and I have certainly enjoyed watching the systematics wars from the sidelines. We should always try to maintain civility but the controversies that arise from different points of view often move a field forward faster and more profitably than would the absence of skepticism about published research.


  • Albin E (1731) A Natural History of Birds : Illustrated With a Hundred and One Copper Plates, Curiously Engraven From the Life. Vol I. London: Printed for the author and sold by William Innys in St. Paul’s Church yard, John Clarke under the Royal-Exchange, Cornhill, and John Brindley at the King’s Arms in New Bond-Street. <available here>

  • Anonymous “N. F.” (1835) Remarks on vernacular and scientific ornithological literature. The Analyst 2: 305–307.

  • Birkhead TR, Montgomerie R (2016) A vile passion for altering names: the contributions of Charles Thorold Wood jun. and Neville Wood to ornithology in the 1830s. Archives of Natural History 43:221–236.

  • Greenoak F (1997) British Birds: their folklore, names, and literature. London: Christopher Helm.

  • Jennings J (1829) Ornithologia, or, the Birds: A Poem, in Two Parts : With an Introduction to Their Natural History; and Copious Notes. London: Sherwood, Gilbert, and Piper. <available here>

  • Stebbins GL. (1982a). Modal themes: a new framework for evolutionary synthesis. in Milkman R (Ed.), Perspectives on Evolution (pp. 12-14). Sunderland, MA: Sinauer Associates.
  • Stebbins GL (1982b) Perspectives in evolutionary theory. Evolution 36:1109–1118.
  • Sterner B, Lidgard S (2017) Moving past the Systematics Wars. Journal of the History of Biology
  • Wood CT (1835) The ornithological guide: in which are discussed several interesting points in ornithology. London Whittaker. <available here>
  • Wood N (1836a) British song birds: being popular descriptions and anecdotes of the choristers of the groves. London: John W. Parker. <available here>
  • WOOD N (1836b) The ornithologists’ text-book: being reviews of ornithological works on various topics of interest. London: John W. Parker. <available here>


  1. Stebbins (1982a) argued that modal themes were often the correct resolution of these conflicts, as has proven to be more-or-less the case in all the controversies listed here, with the notable exception that group selection is still controversial (and mistaken in my opinion)
  2. see, for example, Sterner and Lidgard (2017) for an overview
  3. Tim Birkhead made this discovery while researching for the project on Francis Willughby that he wrote here about a few weeks ago
  4. Linnaeus Systema Naturae had built on Willughby and Ray’s attempt at organizing and logically giving each species a scientific name (Ray (1678), but in the subsequent century there were many attempts to apply Linnaeus system to the birds with each author claiming authority and none of today’s rules about priority, coordination or homonymy.
  5. The International Zoological Congresses of 1889 and 1892 saw the first discussions about some universal rules in zoology but the International Rules on Zoological Nomenclature were not published until 1905.  Earlier, the ornithologist Hugh Strickland had published a set of 22 rules for the formulation of scientific names that formed some of the basis for this later code.
  6. the sex that was so named,  and the county or general area where each name was used, are shown in brackets, from Greenoak (1997).
  7. quotation from Wood 1835a: 238
  8. this was proposed in a paper in The Analyst signed simply N.F. (Anonymous 1835), who I think may well have been Neville Wood based on what N.F. says and the style of writing.
  9. see Birkhead and Montgomerie (2016) for some other gems. The paper is behind a paywall but send me an email if you cannot get it and would like a copy.
  10. ‘callow’ seems to me to be a particularly good adjective to describe these young men, as it refers to someone who is “inexperienced and immature”,  but in the 17th century the term was applied to birds, and meant ‘without feathers’ or immature and not ready to fly.
  11. presented on 7 Jan 1982, at a AAAS symposium marking the 100th anniversary of the death of Charles Darwin; quotation from Stebbins (1982b)

The Sparrow Question

BY: Bob Montgomerie, Queen’s University | 2 Oct 2017

John Gould’s House Sparrow 1873

When I visited England at the beginning of last month, the English House Sparrow (Passer domesticus) was notable for its scarcity. I spent a week in London, Sheffield and the Peak District and only once heard the familiar and once ubiquitous jib-jib (see recent post) in a small park near St Pancras International in central London. Just as well that we don’t call it the ‘English’ Sparrow anymore. Actually they have far from disappeared from the English landscape but their population size did drop by about half from the 1970s to the 1990s, having more-or-less stabilized at present-day numbers by the turn of the millennium.

The precipitous decline in House Sparrow populations in the UK has been well-documented but the causes are thought to be complex—changes in farming practices reducing food availability, competition with other birds, loss of nest sites in cities. and the usual problems with pesticides. Once considered a pest, this species is now of conservation concern in the UK and Europe. North American Breeding Bird Survey data also show a similar decline in numbers from 1966-2004 with a loss of about 2% per year continent-wide.

Because it was so common and readily breeds in nest boxes, the House Sparrow became a model bird species for studies in behaviour and ecology in the latter half of the 20th century, along with species like the Zebra Finch, Rock Pigeon, Red-winged Blackbird, Great Tit, Blue Tit, and Pied Flycatcher. Because it was introduced to North America in the 1850s and spread rapidly across the continent, the House Sparrow was/is considered to be a pest and is not protected by the Migratory Birds Convention Act. This may be one reason that large collections of this bird were possible in the 1960s and 70s for the purpose of looking for morphological evolution (adaptation and drift) across the continent, among other things. The species is still common enough to be the focus of several exciting research programs in both North America and Europe, and has been the subject of more than 5000 papers, at least two ‘recent’ science-based books, and an AOU Ornithological Monograph.


A new paper by Matthew Holmes in the Journal of the History of Biology documents an interesting and largely forgotten period of debate about the House Sparrow in the UK in the late 1800s, one that ushered in a new research discipline called ‘Economic Ornithology’: “Economic ornithology would examine the economic impact of birds on agriculture, a topic neglected by ‘‘recognized text-books on ornithology’’ which only provided readers with ‘‘vague and agriculturally useless statements’’ (Cathcart, 1892).

The debate centred around the sparrow’s influence on agricultural with one side claiming disaster and the other that the bird was at worst harmless, at best beneficial because it consumed insect pests. Thousands of sparrows were slaughtered in the late 1800s both in a vain attempt at control and to collect data on the sparrow’s diet. The House Sparrow, like all good pests, was oblivious to these control attempts and continued to thrive despite widespread concern: “Local meetings of agricultural societies and so-called ‘‘sparrow clubs’’ uniformly condemned sparrows’ consumption of crops. Once labelled as ‘‘vermin,’’ non-productive species were freely persecuted in the fields of Victorian Britain…” A farmer, Charles Newman, encapsulated the attitudes of the day in 1861: “No doubt many persons are opposed to their [sparrows’] destruction, considering that this feathered race were created for some wise purpose. Such was undoubtedly the case in the original order. But the Great Creator made man to rule over the fowls of the air and the beasts of the field, leaving it to his judgment to destroy such that were found more destructive than beneficial.”

In this new paper, Holmes argues that “Nineteenth-century naturalists of all stripes were driven by an overarching sense of purpose, or participation in a grand intellectual endeavour. Acquiring and systematising knowledge gleaned from study of the natural world was associated with moral, religious and social wellbeing.” By the early 20th century this kind of ‘natural history’ had given way to economic ornithology and a general shift to evidence-based science. By the beginning of the 21st century ‘natural history’ was firmly grounded in evidence such that most field biologists are now proud to call themselves natural historians.

Anderson TR (2006) Biology of the Ubiquitous House Sparrow: from genes to populations. Oxford University Press, Oxford
Cathcart AF (1892) ‘Agriculturally economic ornithology.’ The Times, 16 May.
Holmes M (2017) The sparrow question: social and scientific accord in Britain, 1850–1900. Journal of the History of Biology 50:645-671
Kendeigh SC, ed. (1973) A Symposium on the House Sparrow (Passer domesticus) and European Tree Sparrow (P. montanus) in North America. Ornithological Monograph No. 14
Summers-Smith JD (1963) The House Sparrow. Collins New Naturalist Series Monograph No.19, London

Birds and Revolutions

BY: Bob Montgomerie, Queen’s University | 28 Aug 2017

This month [see footnote 1] marks the anniversary of the famous 1858 Darwin-Wallace publication on natural selection published in the Journal of the Proceedings of the Linnean Society of London, Zoology (PDF here). [Note that it was read at a meeting of the Linnean Society on 1 July and published a mere 7 weeks later!] This joint paper ushered in what is arguably the greatest scientific and cultural revolution in human history, a fine example in support of Thomas Kuhn’s (1962) argument that scientific revolutions are driven by ideas. Last week I presented, on this blog, some evidence that tools also fuel revolutions in science.


How did the study of birds figure into Darwin and Wallace’s arguments? We know from Darwin’s many books, and much of Wallace’s writing, that both men studied birds and used examples from birds to illustrate and support many—if not most—of their ideas. This 1858 paper marks the beginning of the association between birds and natural selection. We cannot argue that the study of birds was in any direct way responsible for this scientific revolution but there can be no doubt that this revolution forever influenced how we study birds.

In this publication, Darwin first uses birds as an example of Malthus’s ideas about population:

Suppose in a certain spot there are eight pairs of birds, and that only four pairs of them annually (including double hatches) rear only four young, and that these go on rearing their young at the same rate, then at the end of seven years (a short life, excluding violent deaths, for any bird) there will be 2048 birds, instead of the original sixteen. As this increase is quite impossible, we must conclude either that birds do not rear nearly half their young, or that the average life of a bird is, from accident, not nearly seven years. Both checks probably concur. The same kind of calculation applied to all plants and animals affords results more or less striking, but in very few instances more striking than in man

He then introduces his arguments about sexual selection that he will work on for another 13 years before publishing in 1871 in Descent of Man.

These struggles are generally decided by the law of battle, but in the case of birds, apparently, by the charms of their song, by their beauty or their power of courtship, as in the dancing rock-thrush of Guiana. The most vigorous and healthy males, implying perfect adaptation, must generally gain the victory in their contests. This kind of selection, however, is less rigorous than the other; it does not require the death of the less successful, but gives to them fewer descendants. The struggle falls, moreover, at a time of year when food is generally abundant, and perhaps the effect chiefly produced would be the modification of the secondary sexual characters, which are not related to the power of obtaining food, or to defence from enemies, but to fighting with or rivalling other males.

Wallace also uses birds to illustrate Malthus’s ideas, though, unlike Darwin, he never refers directly to Malthus in his essay:

For example, our own observation must convince us that birds do not go on increasing every year in a geometrical ratio, as they would do, were there not some powerful check to their natural increase. Very few birds produce less than two young ones each year, while many have six, eight, or ten; four will certainly be below the average; and if we suppose that each pair produce young only four times in their life, that will also be below the average, supposing them not to die either by violence or want of food. Yet at this rate how tremendous would be the increase in a few years from a single pair! A simple calculation will show that in fifteen years each pair of birds would have increased to nearly ten millions! whereas we have no reason to believe that the number of the birds of any country increases at all in fifteen or in one hundred and fifty years. With such powers of increase the population must have reached its limits, and have become stationary, in a very few years after the origin of each species. It is evident, therefore, that each year an immense number of birds must perish—as many in fact as are born; and as on the lowest calculation the progeny are each year twice as numerous as their parents, it follows that, whatever be the average number of individuals existing in any given country, twice that number must perish annually,—a striking result, but one which seems at least highly probable, and is perhaps under rather than over the truth.

Finally, I particularly like the following passage from Wallace’s contribution to this publication, where he makes an ecological argument for the abundance of the passenger pigeon:

Perhaps the most remarkable instance of an immense bird population is that of the passenger pigeon of the United States, which lays only one, or at most two eggs, and is said to rear generally but one young one. Why is this bird so extraordinarily abundant, while others producing two or three times as many young are much less plentiful? The explanation is not difficult. The food most congenial to this species, and on which it thrives best, is abundantly distributed over a very extensive region, offering such differences of soil and climate, that in one part or another of the area the supply never fails. The bird is capable of a very rapid and long-continued flight, so that it can pass without fatigue over the whole of the district it inhabits, and as soon as the supply of food begins to fail in one place is able to discover a fresh feeding-ground. This example strikingly shows us that the procuring a constant supply of wholesome food is almost the sole condition requisite for ensuring the rapid increase of a given species, since neither the limited fecundity, nor the unrestrained attacks of birds of prey and of man are here sufficient to check it.

…and continues with ideas about the adaptive significance of migration and factors that influence the relative abundance of species:

In no other birds are these peculiar circumstances so strikingly combined. Either their food is more liable to failure, or they have not sufficient power of wing to search for it over an extensive area, or during some season of the year it becomes very scarce, and less wholesome substitutes have to be found; and thus, though more fertile in offspring, they can never increase beyond the supply of food in the least favourable seasons. Many birds can only exist by migrating, when their food becomes scarce, to regions possessing a milder, or at least a different climate, though, as these migrating birds are seldom excessively abundant, it is evident that the countries they visit are still deficient in a constant and abundant supply of wholesome food. Those whose organization does not permit them to migrate when their food becomes periodically scarce, can never attain a large population. This is probably the reason why woodpeckers are scarce with us, while in the tropics they are among the most abundant of solitary birds. Thus the house sparrow is more abundant than the redbreast, because its food is more constant and plentiful,—seeds of grasses being preserved during the winter, and our farm-yards and stubble-fields furnishing an almost inexhaustible supply. Why, as a general rule, are aquatic, and especially sea birds, very numerous in individuals? Not because they are more prolific than others, generally the contrary; but because their food never fails, the sea-shores and river-banks daily swarming with a fresh supply of small mollusca and crustacea.

Most biologists have read little of what Darwin and Wallace wrote, in part because they think it’s out of date (it’s not) and both convoluted and a bit dry to read (it is, but not uninteresting). If you read nothing else written by these two men, this initial publication, with essays by both of them, is well worth the few minutes invested to read and, particularly, to think about the revolution they started 159 years ago.


Darwin CR (1871) The Descent of Man and Selection in Relation to Sex. John Murray, London.

Darwin CR, Wallace AR (1858) On the tendency of species to form varieties; and on the perpetuation of varieties and species by natural means of selection. Journal of the Proceedings of the Linnean Society of London, Zoology 3:46-50

Kuhn TS (1962) The Structure of Scientific Revolutions. University of Chicago Press, Chicago.


  1. There seems to be some confusion about the actual date. Wikipedia says “the papers appeared in print on 20 August 1858” as does the Royal Society’s twitter feed, which (strangely) links the reader to Wikipedia (see below). Darwin Online, however, says “August 30th, when it appeared in print”.