Saturday 12 November 2022

Vieillot’s Crested Fireback: a colour plate of a pheasant from 1955

In the days when colour printing was extremely expensive, the Avicultural Society had special appeals for funds to support the appearance in Avicultural Magazine of the occasional colour plate. A well-known bird artist was then commissioned. Although the whole run of the Society’s magazines can be found online, the plates rarely see the light of day. Therefore I decided to show one, now and again, on this site.

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This plate from the November-December 1956 issue is Vieillot’s Crested Fireback, a pheasant, also now known as the Malay Crested Fireback, from the Thai-Malay Peninsula and most of Sumatra. It has gone from being considered a subspecies, Lophura ignita rufa, to being split off as a full species, Lophura rufa, in 2014. Jean Delacour (1890-1985), the famous aviculturist and ornithologist, provided a short account of the birds to accompany the colour plate. It is found in lowland forest but now classed as ‘vulnerable’ because of the loss of habitat.

The plate was the work David Morrison Reid Henry (1919-1977) in 1955. He signed his work as D.M. Henry and was an artist favoured by the Avicultural Society for the plates published in this period.

Thursday 10 November 2022

The mystery of ‘Martha’ the last Passenger Pigeon

In a previous article I noted that a Wikipedia entry on Charles Otis Whitman of the University of Chicago stated that he sent the last Passenger Pigeon named ‘Martha’ to Cincinnati Zoo in 1902. Martha died on 1 September 1914 and the species became extinct. The claim that Martha came from Whitman is not supported by some contemporary accounts but can be deduced from another. This is confusing because both accounts arose from the same source.

The 1948 Version

There is no doubt that both Whitman and Cincinnati Zoo bred Passenger Pigeons. Both were unsuccessful in maintaining a breeding stock. An account of Martha’s origins and demise, written by William C. Herman, was published in The Auk. Herman wrote:

The man who, better than anyone else, is qualified to contribute the picture of the final act of this great tragedy is Mr. Sol A. Stephan of the Cincinnati Zoological Gardens in Cincinnati, Ohio (now still living at the age of 97) and from him the present writer obtained much of the information here presented.

Mr. Stephan took charge of the Cincinnati Zoological Gardens in 1878, previous to which time the Zoo had Wild [Passenger] Pigeons on exhibition and had had some success in raising them in captivity. At that time there were four pairs in the aviary which had been purchased in a western locality at a cost of $2.50 per pair; and others were added to this number. At this early date, Wild [Passenger] Pigeons were still to be found in large numbers, and some had visited the beech trees on the grounds that later were taken over by the Cincinnati Zoo. Even at this time Mr. Stephan realized that the Wild Pigeon was becoming scarce. As far back as 1857 a bill to protect it had been proposed by a committee of the Ohio Senate, but no action was taken. As prices became higher, Mr. Stephan became very anxious for the preservation of the species, and he determined to breed the birds in captivity in order to have them for purposes of exhibition. Their habits were carefully observed, with special attention to the diet. He learned that they thrived best on a mixed food of cracked corn, wheat, crackermeal, cooked liver, and eggs. While recent discoveries have been made in the feeding of birds and mammals in captivity, the diet used by Mr. Stephan seemed to be adequate.

Herman then went on to describe the breeding quarters and the nesting. Each nest contained one egg and the birds bred only once a year. Stephan was reported here as having bred 14. The birds became very tame and lived for 10-15 years. Eventually he was left with two birds, one male, one female. Herman continued:

When other zoological gardens learned that the Cincinnati Zoo had the only remaining pair, they offered prices which rose from $100 to $1000 for the pair. At this time Mr. Stephan was not anxious to dispose of such a valuable asset and wisely kept them, for they attracted ornithologists and other scientists from distant parts. The female of this last pair had been hatched in the Cincinnati Zoo in 1885, and was named 'Martha,' in memory of the wife of a friend of Mr. Stephan. This female pigeon became the last survivor of the billions that in flights once darkened the sky.

Martha and her mate built but one nest, and the lone egg that she laid in this proved to be infertile. Since both birds of this last pair were so old that it was apparently impossible for them to rear any young, eggs from Martha were placed under incubating Rock Doves (domestic pigeons), in the hope that the latter might hatch and rear the young to maturity. This failed because the eggs were infertile.

The male of the pair died having been in captivity for 26 years. Martha lived on and died aged 29 (‘an unusually old age in captivity’). She was found dead. Her skin was sent to the United States National Museum in Washington, D.C. Mr. William Palmer, the taxidermist, removed the skin. Dr. Robert W. Shufeldt made an anatomical dissection and published a description of this (Auk, 32: 29-41, pls. 4-6, 1915), giving the cause of death as advanced age’.

The 1908 Version

An account of Whitman’s work with Passenger Pigeons was published in The Auk in 1908 in an article written by Ruthven Deane (1851-1934), a leading amateur ornithologist of his day. Whitman had obtained his birds, as part of his vast study of the evolution of pigeons, from a David W. Whitaker of Milwaukee. A flock of 15 had been bred from a single pair ‘of young birds which he received from a young Indian who trapped them in Shawano County in northeastern Wisconsin’ in 1888. From 1896 to 1897 Whitman bought, in dribs and drabs, the whole flock. During 1897, 9 young were hatched but only four lived. in 1998, he gave 7 birds back to Whitaker. Again eggs were layed by his birds but only 2 hatched. Gradually the flock became depleted as even fewer of the eggs hatched while adults were lost or died. By the end of 1907 all of Whitman’s Passenger Pigeons were dead. He was left with two male Passenger Pigeon x Ring Dove hybrids which he found to be infertile.

Whitaker had four live males in 1908 which died presumably over the next few years.

What is clear from Deane’s paper is that Whitman sent a female bird to Cincinnati Zoo in 1902. But then things get confusing. Deane reported:

For years we have known of the Passenger Pigeons in the Gardens of the Cincinnati Zoölogical Co., and I am much indebted to Mr. S.A. Stephan, General Manager, for the following report of their flock, in a letter written November 9, 1907. 

The original flock, which came from Michigan in 1875, consisted of twenty-six birds, about half males and half females. A short time later, however, five or six of these escaped. They have bred from time to time and we have raised about twenty-three birds. In no instance has more than one egg been deposited at a time. At the present time our flock has been reduced to three, one male from the original flock, now about twenty-three years old, one male, which we raised, is about eighteen years old, and one female that we obtained from Prof. Whitman's flock in 1902, which is about twelve years old. We have never detected any particular disease which has caused the decrease of the flock, but have attributed it in most cases to old age. 

Deane concluded: 

The remnants of the Milwaukee and Cincinnati flocks now number but seven birds (6♂︎, 1 ♀︎) with little or no chance of further reproduction.

This is the version of the story that appeared win the world’s press after the death of the bird in 1914. Further media attention followed the publication of the paper describing the dissection of the bird at the Smithsonian by Robert Wilson Shufeldt (1850-1934) who was medically qualified. In it he wrote:

On February twenty-first, 1914, Mr. S. A. Stephan, General Manager of The Cincinnati Zoological Company, of Cincinnati, Ohio, wrote me that " Our Passenger Pigeon has been promised to the Smithsonian Institution when it dies. This bird is a female and now about 29 years old, and the last one of a flock of eight that we got in 1878." I have since learned that it was hatched in the Garden.

Shufeldt, himself a colourful character with a certain notoriety, noted two things that seem odd. First he wrote:

From Mr. Stephan, who wrote me on the 7th of September, 1914, I learn that "our female passenger pigeon died September 1st [1914] at 1 P. M. of old age, being about 29 years old." It was almost immediately packed in ice and shipped to the National Museum at Washington, D. C., where it was received in fine condition on the fourth of that month.

But external appearances were deceptive. He was with William Palmer of the museum who skinned the birds for taxidermy. Then, after a ‘late lunch’, Shufeldt began his dissection but had a surprise:

I found, on the right side of the abdomen, a slit-like opening, one-half a centimeter in length, which led freely into the abdominal cavity, and from which blood was oozing. This opening I enlarged in order to withdraw the viscera for the purpose of making a photograph of them, previous to proceeding with the dissection of the organs within. This has been my practice for a great many sears. 

Much to my surprise, I found a quantity of blood (not clotted) in the abdominal cavity, and the right lobe of the liver and the intestine almost entirely broken up, as though it had been done with some instrument. As to the intestine, it was missing altogether, while the right lobe of the liver was in scattered fragments The firmer organs were apparently intact, but did not occupy their normal positions.

Later in the paper he continued:

There was no evidence whatever of the presence of the intestine in any part of its continuity save a piece about 8 mm. in length, where it emerged from the gizzard and the ragged margin surrounding the abdominal boundary of the vent. All the portion referred to was not in the abdominal cavity. The entire right lobe of the rather large liver was in a disintegrated condition, showing its internal structure, and exposing the organs usually concealed by it to view. The heart was in its normal position, while the gizzard was rotated to the left side. I discovered no blood clots or parasites of any kind in the abdominal cavity 

The inference from this description and the very detailed of how the bird was received and handled at the Smithsonian is clear: somebody had done something to the specimen in Cincinnati. Had somebody poked and pulled inside the abdominal cavity with a long pair of forceps, the only way I can think of by which the whole intestine and chunks of liver could be removed through a half-centimetre slit? But who, and why?

Also of interest with respect to the alleged age of the birds is:

The feet were of a deep, flesh-colored pink, clean and healthy, while the claws presented no evidences indicative of unusual age, though not a few of wear. 

Two different accounts

The reader of these accounts is therefore in some doubt as to which version, if either, is correct. Both accounts are from the same source, Sol Stephan. In 1908 he wrote that the last surviving female was one sent by Whitman in 1902. The wording in Deane’s article can be taken to imply that this was one of the birds obtained from Whitaker in 1896-7. By contrast, in Shufeldt’s and Herman’s accounts written with information supplied by Stephan after the death of the last bird in 1914, Stephan stated that the female had been hatched in the Cincinnati Zoo in 1885, was named Martha in memory of the wife of a friend, and had died aged 29.

There is a great difference in the age of the last Passenger Pigeon at death, 29, if it the one bred at Cincinnati. If we calculate from Stephan’s account from 1907, then, had the bird come from Whitman, it would have been approximately 19 at its death, much closer to the 10-15 years lifespan quoted for other birds kept in captivity.

Different accounts pre-date the bird’s death. For example, in William T. Hornaday's Our Vanishing Wild Life (1913), the bird is described  as ‘twenty years old in 1912’.

A key question is of course, was possible to know the identities and history of the individual birds at Cincinnati Zoo? Were they ringed (banded in the U.S.A.)? Shufeldt made no mention of one being found at autopsy. I have looked at two photographs of Whitman’s birds that can be seen online and can see no trace of a ring.

All publicity is good publicity: A possible explanation

Salvator A ‘Sol’ Stephan was, in his younger days, a showman, working for a travelling menagerie and also as a representative for Carl Hagenbeck, the famous animal dealer of Hamburg. He arrived at the soon to be opened Cincinnati Zoo in 1875 with an elephant. Persuaded to stay on to settle in the animal, he retired 62 years later as Superintendent and General Manager. He died in 1949 aged 100.

Cincinnati Zoo had a difficult time in its early decades. It entered receivership in 1898 and in order to prevent liquidation the shareholders gave up their investments of nearly a quarter of a million dollars. Then it ran as a business for two years. The Cincinnati Traction Company, hoping apparently to use it as a marketing tool for its streetcars, operated the zoo until 1917 (in some accounts 1915).

I wonder if the opportunity was taken, with the death of the last Passenger Pigeon, to make sure that the attendant publicity (for which Sol Stephan was known) showed the Zoo in the best possible light. What better than a record longevity and the local breeding and care of a bird named Martha?

On the name there is even confusion in the literature. Stephan wrote that she was named after the wife of a friend. Other secondary sources say the name is after Martha Washington, with the male of the final remaining pair as George.

I cannot think of any other explanation, other than a marked loss of memory, for the difference in accounts given by Stephan in 1907 and 1914. In other words, my take on the origins of ‘Martha’ is that she was, most likely, the bird sent to Cincinnati by Whitman in 1902. Shufeldt also remarked that the information he was given by Stephan did not tally with what he was told later:

This bird is a female and now about 29 years old, and the last one of a flock of eight that we got in 1878. I have since learned that it was hatched in the Garden.

As outlined above, I have the feeling from reading between the lines that Shufeldt was suspicious over what he was told about the age of the bird and the circumstances of its death and preservation.

Errol Fuller dealt with the story of Martha’s death in his 2014 book on the Passenger Pigeon:

The truth is that we don't actually know when Martha died, at least not with any degree of exactitude. This lack of definitive information is largely due to differing accounts given by the main keeper at the zoo, Salvator "Sol" Stephans, and his son Joseph. Both kept changing their story. One of their accounts states that Martha died in her cage at precisely one o'clock on the afternoon of Tuesday, September 1, 1914. Another suggests her death might actually have occurred some four hours later. One version of the story relays the romantic idea that she died surrounded by a group of grieving keepers. Another maintains that just Sol and Joseph were with her. Yet another is less poetic and indicates she died alone and was found lying on the floor of her cage by an assistant keeper named William Bruntz. The truth hardly matters, of course. Dead is dead.

Furthermore, any serious attempt to go through written zoo records to solve the mystery is impossible; they were destroyed by fire in 1963. What we do know is that the first day of September was a swelteringly hot day with high humidity levels; perhaps it was all just too much for a frail old bird. So what else is there? The answer is, not a lot. It seems certain that Martha was born in captivity, but where? Mr. Stephans' recollections were as varied on this subject as they were on others. Perhaps this was due to captivity, but where? Mr. Stephans' recollections were as varied on this subject as they were on others. Perhaps this was due to poor note keeping; perhaps it was forgetfulness or just a lack of knowledge concerning past events that at the time of their occurrence would have seemed unimportant.


What would happen now?

The accounts by ornithologists and aviculturists describe the failure of the faltering and early attempts at what would today be described as a captive breeding programme for a highly endangered species. A useful discussion might be had on whether, with the vast increase in knowledge of wild animal husbandry, we could have done any better in 2022. What stands out in reading the accounts is: the failure of eggs to hatch (still a major problem), which could be related to infertility, or to poor conditions for incubation; the decline in fecundity as the females aged; the degree of inbreeding. All Whitaker’s and therefore Whitman’s birds were descended from a single pair of young birds which had been hand reared. My bet is they were from the same nest. Therefore, inbreeding depression could account for some of Whitman’s findings (a phenomenon he described as ‘weakness of the germ’) and that explanation appeared in print in 1913. The group originally kept in Cincinnati was larger and therefore more genetically diverse. Nevertheless that population also declined over the years. Nutrition may also have been inadequate in captive birds. Wallace Craig recorded the behaviour of Whitman’s birds. He wrote:

A word as to the care of Passenger Pigeons, in case we may be so fortunate as to find some still living. Professor Whitman kept his in the same pen with other species, supplied with the pigeonstaples of mixed seed, grit, oyster shells, salt, and plenty of green food such as lettuce. After he had had his flock many years, he discovered that they would greedily devour earthworms, and when abundantly supplied with this delicacy the birds improved so much in health and vigor that Professor Whitman thought if only he had known of this diet early enough he might have saved his stock from dying away.


As unsatisfactory as the different accounts of the death of what is still presumed to be the last Passenger Pigeon (Ectopistes migratorius) are, they are immaterial to the extinction of the species that occurred over a relatively short period. I started this series of two articles with the achievements of Oscar Riddle in discovering, firstly, the hormone prolactin and, secondly, the latter’s effect on the pigeon crop sac. Because of Riddle’s close links to Charles Otis Whitman, I became fascinated by the history of the extinction of the Passenger Pigeon and of those who kept and bred the bird in captivity. I still have much more to read.

Martha's feathers were not in very good condition when she died and
her skin was not displayed by the National Museum in Washington for
many years. However, it is now on display, as described here.
Photographed in 2015 by Ph0705.

Deane R. 1896. Some notes on the Passenger Pigeon (Ectopistes migratorius) in confinement. Auk 13, 234-237.

Deane R. 1908. The Passenger Pigeon (Ectopistes migratorius) in confinement. Auk 25, 181-183.

Fuller E. 2014. The Passenger Pigeon. Princeton and Oxford: Princeton University Press.

Grant W. 1913. Recollections of the Passenger Pigeon in captivity. Bird Lore 15,  93-99

Herman WC. 1948. The last Passenger Pigeon. Auk 65, 77-80.

Shufeldt RW. 1915. Notes on the Passenger Pigeon (Ectopistes migratorius) lately living in the Cincinnati Zoölogical Gardens. Auk 32, 29-41.


Tuesday 8 November 2022

What—and who—connects the last Passenger Pigeons with the discovery of a hormone?

Oscar Riddle was a scientist who came good. After an inauspicious and tedious early research career he is remembered for discovering the hormone prolactin. Prolactin from the pituitary gland is essential for lactation as well as being involved in a whole host of physiological processes in vertebrates, acting both through the blood stream as a hormone and as a local controlling factor within tissues and organs.

Oscar Riddle
from here
Around 1930 Riddle became interested in trying to find the stimulus to milk secretion. He knew of then recent research which showed that aqueous extracts of the anterior pituitary will induce milk secretion in rabbits. Attempts by others to isolate and identify the chemical factor had, however, failed. With the assistance of a chemist he had taken on, Robert Wesley Bates (1904-1994), and of Simon W. Dykshorn, a research student, he succeeded in isolating a compound that had the stimulatory effect on the mammary gland but was not the same as the putative hormones present in anterior pituitary extracts which affected other tissues and organs. Riddle had a new hormone, and the name he gave it, prolactin, still stands.

Working on something mammalian was a major diversion for Riddle. He had for over 20 years   worked almost exclusively on pigeons, particularly in the 1920s on metabolism, reproduction and endocrinology. He was therefore well prepared to ask the simple question, is the secretion of crop ‘milk’ in pigeons also stimulated by his newly-extracted hormone. Yes, was the answer and Riddle, Bates and Dykshorn soon developed the pigeon crop sac as a bioassay for prolactin activity. The lasting importance of this discovery is sometimes overlooked by modern endocrinologists who all seem to be based in the increasingly inward looking sub-discipline of clinical endocrinology. Because they had to wait until the 1970s for a reliable method of measuring the concentrations of prolactin in blood, the bioassay is of no interest. However, it continued to be used, certainly into the 1980s, by those looking for prolactin-like hormones produced in other tissues, the physiologically very important placental lactogens produced by the placenta, for example.

On 26 December 1932, shortly after the publication of their work, Simon Dykshorn, variously described then as a research student or research fellow, was found shot dead in woods, where he had gone hunting, about a mile west of the Cold Spring Harbor Laboratory on Long Island, New York, where Riddle had worked since 1912. Dykshorn was 30.

After this tragedy, with Bates and Ernest Lester Lahr (1897-1982), Riddle went on to further purify their prolactin preparation and to identify it as a protein.

Riddle's Prolactin Team
From Family Trees on

The reason Riddle had spent much of his time studying pigeons and making little headway for some years was that he completed his PhD in Chicago under the supervision of Charles Otis Whitman. Whitman was trying to find the cause of the pattern of alternate light and dark bars on the feathers of many species of birds. This question arose out of Whitman’s long interest in the evolution of birds. There were many dead ends and misinterpretations, not helped by Whitman’s rejection of both Mendelian genetics and natural selection. His devotion to the study of pigeons was such that he worked increasingly at home where for a period of 15 years he usually had around 500 individuals of 40 species in dovecotes around his house. He hybridised 40 species. Foy years Whitman moved his pigeons each summer to Marine Laboratory at Woods Hole in Massachusetts (where had had been its director) by rail, and then moved them back to Chicago in September. Initially the University of Chicago paid for the pigeons to be moved but then refused and thereafter Whitman and his wife paid.

Riddle valued highly the companionship and guidance of Whitman. He wrote: ‘Whitman became nearer to being a father to me than anyone I have known.’ Whitman died suddenly in 1910, aged 57. Riddle undertook to write up Whitman’s work. However, the new regime in Chicago, not impressed by Whitman’s research, did not want his disciple. Whitman though had been a influential figure in American zoology and In 1912, the Carnegie Institute of Washington took on Riddle as a research associate, together with Whitman’s pigeons and papers. By 1913 all were ensconced at Cold Spring Harbor. There is something odd in that the director of the lab, Charles Benedict Davenport (1866-1944), must have acquiesced to Riddle’s appointment—perhaps he had no choice—but did nothing to provide him with adequate facilities. Whitman’s views were the exact opposite of the main thrust of work, Mendelian genetics, at the lab and it must have come as some embarrassment when Whitman’s work was eventually pulled together over the next 6 years and published in three volumes, when the title of the first was Orthogenetic Evolution in Pigeons. Whitman really believed he had demonstrated orthogenetic evolution or evolution along pre-determined pathways. However, Davenport wrote an extensive obituary of Whitman. Perhaps they were friends and Davenport felt under some obligation to provide some means of concluding Whitman’s work while not appreciating the direction Whitman was heading. In the meantime Davenport was earning opprobrium of his own as one of the leading American exponents of eugenics. His views were so extreme and his notions from Mendelian genetics so warped that other eugenicists disowned him. He was, and remained, a supporter of the Nazi party in Germany before and during the Second World War. Perhaps then there is a simpler explanation for Davenport’s lack of support for Riddle: was neither a Mendelian geneticist nor a eugenicist who did not fit into Davenport’s organisation.

Whitman with his pigeons
From here

Most of the immense amount of work to sort and write up Whitman’s notes fell to Riddle. But even this labour of love ran into difficulties. For some reason, Whitman’s widow did not allow Riddle access to all of her husband’s papers. The very long and arduous episode in Riddle’s life must be one of the best illustrations of ‘no good deed goes unpunished’. The publications were not well received, particularly the one on orthogenesis. Reviewers of that volume pointed out that many of his ideas had already been, in kinder words, shot down in flames. The three volumes can be found online and even a quick look provides some appreciation of the amount of work and the level of detail involved. Two artists were engaged to provide the colour plates and other illustrations. The cost to the Carnegie Institute must have been enormous.

Volume 1 of the posthumous works of Whitman

Eventually, Riddle, by developing interests in how birds work and into the burgeoning fields of metabolism and endocrinology, pulled away from Whitman’s ideas on evolution. He was by 1930 very well equipped to discover something really important.

And it was Whitman who provides the link I referred to in the title of this article. Lord Walter Rothschild in his 1907 book, Extinct Birds, quoted from notes sent to him by James H. Fleming of Toronto”

For all practical purposes, the close of the Nineteenth Century saw the final extinction of the Passenger Pigeon in a wild state, and there remained only the small flock, numbering in 1903 not more than a dozen, that had been bred in captivity by Prof. C. O. Whitman, of Chicago; these birds are the descendants of a single pair, and have long ago ceased to breed. It was in an effort to obtain fresh blood for this flock that I started a newspaper enquiry that brought many replies, none of which could be substantiated as  records of the Passenger Pigeon, and many referred to the Mourning Dove. I am aware that there has been lately wide-spread and persistent rumours of the return of the pigeons, but no rumour has borne investigation, and I feel that Prof. Whitman's small flock, now reduced (in 1906) to five birds, are the last representatives of a species around whose disappearance mystery and fable will always gather.

Rothschild’s correspondent seems to have overlooked the Passenger Pigeons at Cincinnati Zoo, where they had also bred and where the last one, ‘Martha’, died in 1914. The entry for Whitman on Wikipedia states that he sent Martha to Cincinnati in 1902. However, some contemporary evidence indicates that was not the case while another account—from the same source—suggests that the last living Passenger Pigeon was one received from Whitman. I will return to Martha and her origins in another article.

Oscar Riddle was elected to the U.S. National Academy of Sciences in 1939 for his work on prolactin. It was as a result of his earlier career with Whitman that he realised the importance of studying the effect of prolactin on the pigeon’s crop. The results of that second discovery were then developed into a vital bioassay that was used—and could well be still used—throughout the world for studying the biological activity prolactin-like compounds in all vertebrates.

Riddle was a major player in his later life in promoting the study and teaching of evolution in the USA where belief in the supernatural then—and still does—trumps rationality. He really did, after a shaky start, come good.

Oscar Riddle died on 29 November 1968, aged 91.

Female Passenger Pigeon by K. Hayashi
K. Hayashi and K. Toda were the artists commissioned to provide the illustrations
to Whitman's posthumous works. This is from Volume 2

Corner GW. 1974. Oscar Riddle 1877-1968. National Academy of Sciences. Biographical Memoirs: Volume 45. p 448-488. Washington, DC: The National Academies Press.

Davenport, CB. 1917. The personality, heredity and work of Charles Otis Whitman. 1843-1910. American Naturalist 51, 5-30.

Wednesday 2 November 2022

Shedding light on gulls’ eggs: how light exposure triggers different development in the last egg of a clutch

In one of those quirks of circumstance a photograph of a much smaller than usual Black-headed Gull appeared on the Ayrshire Nature Facebook page. A short time later, news of a new paper offering a possible explanation arrived in my inbox.

In gulls the young hatch in the order in which eggs are laid. Small young gulls are those that hatched last and are at the receiving end of intense competition for resources from their earlier hatched siblings. These last hatched chicks are known to exhibit a resilient “junior phenotype” ‘characterized by accelerated hatching, increased begging behavior and a slower growth rate’. Is there some cue from the outside world that causes them to develop these physiological and behavioural features?

Francisco Ruiz-Raya, Jose Noguera and Alberto Velando of the University of Vigo in Spain considered that light might be the trigger for changing the pre-hatching development to the junior phenotype. As senior birds hatch, the parents spend less time incubating and more time feeding them. The last egg is therefore exposed to light for longer. To test the hypothesis they studied Yellow-legged Gulls (Larus michahellis), which lay three eggs per clutch at intervals of 1-3 days with incubation beginning after the second egg is laid. Junior birds typically hatch 1-3 days after their siblings. The difference of exposure of the eggs to light was marked. Third-laid eggs spent 82% of their time exposed to high light intensities during a six-hour period two days before hatching. By contrast senior eggs spent only 0.05% of their time. If light is the trigger, then the signal is loud (well, bright) and clear.

Yellow-legged Gull (Larus michahellis) in the Gulf of Olbia (Sardinia, Italy)
Gzzz, CC BY-SA 3.0 <>, via Wikimedia Commons

By manipulating the exposure of eggs to light it became clear that the junior phenotype of the can indeed be triggered by their exposure to light while still in the egg. The authors also found corresponding physiological changes associated with different patterns of gene expression. Somehow light exposure at perhaps a critical time before hatching results in the production of chicks with different physiological and behavioural characteristics from the same clutch of eggs.

Ruiz-Raya F, Noguera JC, Velando A. 2022. Light received by embryos promotes postnatal junior phenotypes in a seabird. Behavioral Ecology