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

The Spring Rivalry of Birds

BY: Bob Montgomerie, Queen’s University | 28 May 2018

Unless you have been living in a cave for the past couple of months, you will have been well aware of the spectacle of mature, powerful males posturing to one another, showing off their weapons, advertising their prowess, and intimidating their neighbours. Some of them even coerced females into unwanted sexual acts, or spent some time cheating on their mates. I refer, of course, to what Charles Bethune Moffat called ‘The Spring Rivalry of Birds‘ in his 1903 paper in The Irish Naturalist.

American Coots fighting at a territory boundary (PHOTO Bruce Lyon)

Moffat was born in January 1859 on the Isle of Man in the Irish Sea, 10 months before the publication of Darwin’s Origin of Species. Moffat’s family soon moved to Ireland where he grew up and eventually spent his entire professional career as a lawyer and journalist.

IrishNatBut Moffat was also a consummate naturalist who published about birds in popular articles in Dublin’s Daily Express, and in scientific papers in The Irish Naturalist [1] and The Irish Naturalists’s Journal. His paper on the ‘spring rivalry’ is best known because it was probably the first publication to present, in English [2], the idea that male birds defend a territory: “…that the battles fought between the male birds in spring have for their object, not the winning of particular females, but the acquiring of suitable plots of land, and that the song and bright plumage of the male are a warning to other males and an intimation to a female that a suitable territory has been acquired.” [3]

Reading Moffat’s spring rivalry paper, I get the distinct impression of a man who was thoughtful, logical and a keen observer—all traits that would have made him an excellent lawyer and journalist (both of which he was) and a really good scientist. He noted, for example, “…that we seldom find in close proximity to each other two nests belonging to the same species of bird.”, “…that cock birds in early spring spend a great deal of their time in fighting one another.”, and “..that we must have a very large number of non-breeding birds of both sexes, prevented from breeding simply by the fact that they have no suitable ground.” [3]

Moffat liked Darwin’s ideas about evolution and natural selection but he thought—like many others at the time—that Darwin was simply wrong about sexual selection, especially with regard to female choice:

…the number of hen-birds, so far as we can gather, is fully equal to the number of cock-birds, so that when all the fighting is over, there is nothing to prevent all the birds from marrying and settling down to ‘ live happily ever after.’ We may suppose, in our sentimental way of looking at things, that even then the poor beaten cock-bird suffers from a certain amount of depression when he thinks of the greater charms of her to whom he first paid court. But we have the assurance of experts that no such thing happens; that one hen-bird is quite as good as another, and that every cock-bird is perfectly content with the first mate he can get. That is sometimes laid down as the reason why hen-birds, as a rule, have not developed bright nuptial colours or melodious voice…I think we must infer that there is very little free choice or aesthetic selection, and that the hen bird is mainly guided by prudential motives in accepting the owner of the soil. [3]

Dark-eyed Junco fighting his reflection in a car window (PHOTO: Bruce Lyon)

Having observed male Blackbirds and Chaffinches continually battling their reflections in his windows, Moffat quite perceptively concluded that these fights were about space, as there was no female in sight and those reflected interlopers had nether sung nor shown any interest in the male’s mate: “the imaginary enemies, on whom so much fury was expended, were guilty of no crime beyond that of being in the spot where they were.” [3]. Even when 35 Starlings were shot one at a time, consecutively, from a single breeding pair, the remaining bird almost immediately got a new partner, suggesting to Moffat that birds did not really care who they mated with, and that space was therefore of primary importance.

But why ‘space’? Moffat was also skeptical about Darwin’s idea that—at least in birds—many more offspring are produced than could possibly survive to reproduce: “I cannot believe that the theory of Natural Selection — for which I have a great respect, and which I must carefully guard myself against appearing for a moment to call in question— requires this sacrifice, or anything like it…as regards birds I am altogether unable to find grounds for believing in so great a death-rate..” [3]. Indeed, his censuses of his local House Martins suggested to him that the annual mortality rate was very low, for just about as many birds arrived back in spring as had departed the previous autumn [4].

VCWE1962His solution to this conundrum of territoriality—anticipating V. C. Wynne-Edwards’s ideas on group selection published 60 years later—was: “..that there are checks of a prudential kind on the marriage of birds, and that these checks may be a very important factor in keeping the number of birds absolutely permanent.” [3]. Thus Moffat argued that birds were simply being prudent, dividing up the available land in such a way that would keep the population stable, without the needless waste of reproduction wherein the excess individuals would die off as Darwin had argued.

He was certainly not alone in his skepticism about sexual selection and population regulation, and it took the reaction to Wynne-Edwards’s ideas—mainly by David Lack and George Williams—to set the record straight with regard to the logic of natural selection. And that set the stage for a re-examination of sexual selection and its influence on the songs, plumage colours and ornaments, and courtship behaviours of birds—traits that benefit individuals not species.

So, next time you hear the twitter of North America’s Orange-crowned Warbler, see European Coots threaten their neighbours, watch the Siberian Grouse perform his flutter-jump, or hear the Oriental Cuckoo whistle his ridiculous ‘poo-poo’, remember that none of this male behaviour is performed for the good of the species.


  • Altum B (1868) Der Vogel und sein Leben. Münster: Niemann. [available here]

  • Kennedy PG (1946) Charles Bethune Moffat. (1859-1945). British Birds 39:81–82.

  • Moffat CB (1903) The spring rivalry of birds. Some views on the limit to multiplication. The Irish Naturalist 12:152–166.

  • Stresemann E (1947) Baron von Pernau, pioneer student of bird behavior. The Auk 64:35–52.

  • von Pernauer FJA [published anonymously without his consent] (1702) Unterricht, was mit dem lieblichen Geschöpff, denen Vögeln, auch ausser dem Fang, nur durch die Ergründung deren Eigenschafften und Zahmmachung oder anderer Abrichtung, man sich vor Lust und Zeitvertreib machen könne, gestellt Durch den Hoch- und Wohlgeborhrnen Hn. Freyherrnn: Herrn von P [ available here]
  • White G (1772) Letter XI to The Honourable Daines Barrington. [available here]

  • Wynne-Edwards VC (1962) Animal Dispersion in Relation to Social Behaviour. Edinburgh: Oliver and Boyd.


  1. papers in Irish Naturalist: he published 40 papers and short notes in this journal, as well as 40 book reviews
  2. first presentation in English: Ferdinand Johann Adam von Pernauer (1702) and, especially, Bernard Altum (1868) had previously introduced and developed the idea of territoriality and the concept of ‘territory’ in birds. Moffat also notes that Gilbert White had a similar view that he expressed in a letter written in 1772: “such a jealousy prevails between the male birds that they can hardly bear to be together in the same hedge or field…it is to thisspirit of jealousy that I chiefly attribute the equal dispersion of birds in the spring over the face of the country.”
  3. quotations: all from Moffat (1903)
  4. House Martin observations: his mistake here is that he assumed that these were the same individuals, not realizing that overwinter mortality would have left openings to be filled by birds that might otherwise have been non-breeders

Professor Bumpus and his Sparrows

Guest Post

BY: Ted R. Anderson | 5 March 2018

Possibly the most influential ornithological paper published inNorth America in the 19th century was actually written by an invertebrate embryologist who was not even a member of the American Ornithologists’ Union.  The paper “The elimination of the unfit as illustrated by the introduced sparrow, Passer domesticus” was written by Professor Hermon Carey Bumpus at Brown University in Providence, Rhode Island  It was actually the second of two interesting papers that Bumpus published on the recently introduced house sparrow, but more on these below.

Hermon Bumpus

Bumpus was born in Maine in 1862, and entered Brown in 1879 to study biology, graduating in 1884.  In 1886, he accepted a professorship at Olivet College in Michigan, a position he left in 1889 to complete a doctorate at the newly established Clark University, where he received the first PhD awarded by that university.  In 1890 he returned to Brown as assistant professor of zoology and was promoted to professor of comparative anatomy two years later.  He left Brown in 1900 to become assistant to Morris Jessup, president of the board of the American Museum of Natural History in New York City.  A year later Jessup promoted him to become the museum’s first director.

In 1911 Bumpus moved into academic administration as business manager of the University of Wisconsin, a position he held until 1914.  He then moved to Tufts College (now University) as President from 1915 to 1919.  He resigned from Tufts to pursue his interest in building or remodeling homes including a Philippine bungalow on Long Island Sound (constructed of Philippine lumber from the Philippine Hall at the St. Louis Exposition), an Italian villa in a Boston suburb and the King Caesar House in Duxbury, Mass.  Bumpus died in Pasadena, California in 1943.

pexels-photo-460960.jpegWhile teaching at Brown, Bumpus spent his summers conducting research on the development of marine invertebrates at the Marine Biological Laboratory at Woods Hole, Massachusetts, where he also served as assistant director from 1893 to 1895, and as director of the Biological Laboratory of the US Fish Commission.  In 1896 he presented the inaugural lecture in a summer seminar series at the Marine Biological Laboratory entitled “The variations and mutations of the introduced sparrow, Passer domesticus”, which was published in 1898.

In that 1898 paper he was undoubtedly the first scientist to suggest that the introduction of house sparrows and their subsequent rapid spread across North America represented a huge experiment that could be used to study Darwinian natural selection.  Taking advantage of that natural experiment, he compared the size, shape and coloration of 868 sparrow eggs from Massachusetts with an equal number of sparrow eggs from England, to test the hypothesis that the rapid population growth of sparrows in North America would result in relaxed selection.  Without the benefit of statistical analysis—Francis Galton and Karl Pearson were just then developing some rudimentary statistical tests—he concluded from his graphs that eggs from Massachusetts were shorter and more variable in size and coloration than eggs from England.  He also raised the question of whether the observed differences were phenotypic (‘ontogenetic’) or adaptive (‘phylogenetic’) and suggested that a common garden experiment would be needed to differentiate between these alternatives.

Bumpus’s graph of the length of house sparrow eggs from North America (dotted line) and Europe (solid line) [1]

On 1 February 1898, a winter storm in Providence provided Bumpus with the material for another summer lecture at Woods Hole, which he then published.  After the storm, 136 immobilized sparrows were brought to Bumpus’s anatomy lab, where 72 subsequently revived but the remaining 64 died.  Bumpus identified the sex and measured nine morphological traits of each bird.  Bumpus concluded from his graphs that males survived better than females and that shorter, lighter birds with longer legs, wings and sternums and larger brain size (“skull width”) also survived better. He concluded that his analyses showed:

Natural selection is most destructive of those birds which have departed most from the ideal type, and its activity raises the general standard of excellence by favoring those birds which approach the structural ideal.

…the birds which perished have certain average structural peculiarities which distinguish them from the survivors, and that the intensity of selective elimination has been felt most by birds of extreme structure [2]

In his 1899 publication, the entire dataset is reproduced in an appendix, thereby permitting many other evolutionary biologists, as well as innumerable students in evolution classes, to analyze Bumpus’s data statistically.  Harris published the first  statistical analysis, and at least ten other papers have been published since then, including papers by John Calhoun, Peter Grant , Richard F. Johnston and colleagues, and one by Russell Lande and Steven Arnold.  Increasing complex and sophisticated statistical analyses were employed in these papers, and the conclusions of the various authors differ from those of Bumpus and from each other, in part due to the fact that many of the analyses use only subsets of the original data.

I do not know of another dataset of birds that has been subjected to so many analyses and so many different interpretations The history of reanalysis of Bumpus’s data is a nice example of a century of progress in both statistics and evolutionary biology


  • Anderson TR (2006) Biology of the Ubiquitous House Sparrow, from Genes to Populations. Oxford: Oxford University Press
  • Bumpus HC (1898) The variations and mutations of the introduced sparrow, Passer domesticus. Biological Lectures Delivered at the Marine Biological Laboratory of Woods Holl, 1896-1897, pp. 1-15.
  • Bumpus HC (1899) The elimination of the unfit as illustrated by the introduced sparrow, Passer domesticus. Biological Lectures from the Marine Biological Laboratory of Woods Holl, Mass. 1898, pp 209-228.
  • Calhoun JB (1947) The role of temperature and natural selection in relation to the variations in size of the English sparrow in the United States. American Naturalist 81:203-228.
  • Grant PR (1972) Centripetal selection and the house sparrow. Systematic Zoology 21:23-30.
  • Harris JA (1911) A neglected paper on natural selection in the English sparrow. American Naturalist 45:314-319.
  • Johnston RF, Niles DM, Rohwer SA (1972) Hermon Bumpus and natural selection in the house sparrow Passer domesticus. Evolution 26:20-31.
  • Lande R, Arnold SJ (1983) The measurement of selection on correlated characters. Evolution 37:1210-1226.


  1. graph: Bumpus 1898 page 5
  2. quotation: Bumpus 1899 pages 217 and 218