Red Bill Research Articles

Evaluating different metrics to study small color differences: the red bill and plumage of common waxbills as a case study

Evaluating different metrics to study small color differences: the red bill and plumage of common waxbills as a case study

Second Records of the Caspian Tern Hydroprogne caspia in Lebanon 2022

Caspian Tern Hydroprogne caspia is a monotypic, cosmopolitan species occurring in North America, North Europe, Africa, Madagascar, Asia, Australia, and New Zealand. There are only three European populations of approximately 4,500 breeding pairs along the coasts of the Caspian, Black, and Baltic Seas. It’s the largest of the terns, with a wingspan averaging. It has a body length of 48 - 56 cm, a weight of 570-780 gram and a wing span of 127-140 cm. Its size, stout red bill, and lack of a deeply forked tail distinguishes it from other white terns found in the state. Its black cap, large red bill, and tern-like habit of flying slowly with its bill pointed downward separates it from the gulls. The low harsh call of the Caspian tern sounds similar to karrr or kraa-ah and is given frequently while in flight. The orange feet of immature birds distinguish them from fall-plumaged adults which have black feet. Recently it was recorded for the first time in Lebanon in 15th of September 2021 and the second record was made in 18th of January 2022, both records were made by Michel Sawan in north Lebanon.

First Records of the Caspian Tern Hydroprogne caspia in Lebanon 2021

Caspian Tern Hydroprogne caspia is a monotypic, cosmopolitan species occurring in North America, North Europe, Africa, Madagascar, Asia, Australia, and New Zealand. There are only three European populations of approximately 4,500 breeding pairs along the coasts of the Caspian, Black, and Baltic Seas. It’s the largest of the terns, with a wingspan averaging. It has a body length of 48 - 56 cm, a weight of 570-780 gram and a wing span of 127-140 cm. Its size, stout red bill, and lack of a deeply forked tail distinguishes it from other white terns found in the state. Its black cap, large red bill, and tern-like habit of flying slowly with its bill pointed downward separates it from the gulls. The low harsh call of the Caspian tern sounds similar to karrr or kraa-ah and is given frequently while in flight. The orange feet of immature birds distinguish them from fall-plumaged adults which have black feet. Recently it was recorded for the first time in Lebanon in 15th of September 2021 at Cheikh Zennad, Akkar District, North Lebanon by Michel Sawan.

Testosterone, signal coloration, and signal color perception in male zebra finch contests.

Many animals use assessment signals to resolve contests over limited resources while minimizing the costs of those contests. The carotenoid-based orange to red bills of male zebra finches (Taeniopygia guttata) are thought to function as assessment signals in male-male contests, but behavioral analyses relating contest behaviors and outcomes to bill coloration have yielded mixed results. We examined the relationship between bill color and contests while incorporating measurements of color perception and testosterone (T) production, for an integrative view of aggressive signal behavior, production, and perception. We assayed the T production capabilities of 12 males in response to a gonadotropin-releasing hormone (GnRH) challenge. We then quantified the initiation, escalation, and outcome of over 400 contests in the group, and measured bill color using calibrated photography. Finally, because signal perception can influence signal function, we tested how males perceive variation in bill coloration, asking if males exhibit categorical perception of bill color, as has been shown recently in female zebra finches. The data suggest that males with greater T production capabilities than their rivals were more likely to initiate contests against those rivals, while males with redder bills than their rivals were more likely to win contests. Males exhibited categorical color perception, but individual variation in the effect of categorical perception on color discrimination abilities did not predict any aspects of contest behavior or outcomes. Our results are consistent with the hypotheses that T plays a role in zebra finch contests and that bill coloration functions as an aggressive signal. We suggest future approaches, based on animal contest theory, for how links among signals, perception, and assessment can be tested.

Ecological effects on female bill colour explain plastic sexual dichromatism in a mutually-ornamented bird

Sex differences in ornamentation are common and, in species with conventional sex roles, are generally thought of as stable, due to stronger sexual selection on males. Yet, especially in gregarious species, ornaments can also have non-sexual social functions, raising the possibility that observed sex differences in ornamentation are plastic. For example, females may invest in costly ornamentation more plastically, to protect body and reproductive ability in more adverse ecological conditions. We tested this hypothesis with experimental work on the mutually-ornamented common waxbill (Estrilda astrild), supplementing their diets either with pigmentary (lutein, a carotenoid) or non-pigmentary (vitamin E) antioxidants, or alleviating winter cold temperature. We found that both lutein and vitamin E supplementation increased red bill colour saturation in females, reaching the same mean saturation as males, which supports the hypothesis that female bill colour is more sensitive to environmental or physiological conditions. The effect of vitamin E, a non-pigment antioxidant, suggests that carotenoids were released from their antioxidant functions. Alleviating winter cold did not increase bill colour saturation in either sex, but increased the stability of female bill colour over time, suggesting that female investment in bill colour is sensitive to cold-mediated stress. Together, results show that waxbill bill sexual dichromatism is not stable. Instead, sexual dichromatism can be modulated, and even disappear completely, due to ecology-mediated plastic adjustments in female bill colour.

Carbon δ13C Isotopic Marker Values Correlate with Carotenoid-Based Bill Colouration in Adult Yellow-Legged Gulls Larus michahellis

La coloracion basada en carotenoides que presentan muchas aves puede reflejar honestamente la calidad del individuo, ya que deben ser obtenidos mediante la dieta. Estos pigmentos son importantes para varias funciones fisiologicas y los individuos pueden buscar compensar entre la distribucion de los carotenoides para estos usos y su acumulacion para atributos sexuales secundarios y sociales. La gaviota patiamarilla Larus michahellis es una especie oportunista que se alimenta de una gran variedad de presas. En este trabajo hemos estudiado si la coloracion basada en carotenoides (pico, mancha roja, anillo orbital) esta relacionada con la ecologia trofica inferida a partir de la composicion isotopica de plumas de aves adultas en tres colonias de esta especie. El marcador isotopico del δ13C correlaciono negativamente con la coloracion basada en carotenoides (area de la mancha roja). Contrariamente a la prediccion hecha a priori, el marcador indica que un mayor consumo de presas terrestres y recursos de vertedero podria ayudar a generar una mancha roja del pico mayor en gaviotas de cualquier sexo. En hembras, no se detecto ninguna correlacion entre las signaturas isotopicas y el volumen de los huevos. El resultado de que un consumo mayor de presas marinas implica una mancha roja menor apoya otros descritos en estudios anteriores que muestran efectos aparentemente positivos de comer en ambientes terrestres humanos sobre el fenotipo de aves adultas. Los resultados pueden sugerir que un mayor consumo de presas marinas puede no ser tan positivo como el presentado en estudios previos. Sin embargo, el efecto de los componentes toxicos potenciales que se pueden obtener de algunas fuentes de alimentacion deberia ser estudiado mas a fondo. Deberiamos de considerar tambien los probables efectos subletales retardados asociados a estos habitats y que se ejercerian sobre los adultos y, probablemente tambien, sobre los pollos.

Genetic Basis of De Novo Appearance of Carotenoid Ornamentation in Bare Parts of Canaries

Unlike wild and domestic canaries (Serinus canaria), or any of the three dozen species of finches in genus Serinus, the domestic urucum breed of canaries exhibits bright red bills and legs. This novel trait offers a unique opportunity to understand the mechanisms of bare-part coloration in birds. To identify the mutation producing the colorful phenotype, we resequenced the genome of urucum canaries and performed a range of analyses to search for genotype-to-phenotype associations across the genome. We identified a nonsynonymous mutation in the gene BCO2 (beta-carotene oxygenase 2, also known as BCDO2), an enzyme involved in the cleavage and breakdown of full-length carotenoids into short apocarotenoids. Protein structural models and in vitro functional assays indicate that the urucum mutation abrogates the carotenoid-cleavage activity of BCO2. Consistent with the predicted loss of carotenoid-cleavage activity, urucum canaries tended to have increased levels of full-length carotenoid pigments in bill tissue and reduced levels of carotenoid-cleavage products (apocarotenoids) in retinal tissue compared with other breeds of canaries. We hypothesize that carotenoid-based bare-part coloration might be readily gained, modified, or lost through simple switches in the enzymatic activity or regulation of BCO2 and this gene may be an important mediator in the evolution of bare-part coloration among bird species.

Release from ecological constraint erases sex difference in social ornamentation

Sex differences in animal ornamentation are thought largely genetically fixed due to stronger sexual selection on males of species with conventional sex roles. But, other types of sex differences are not genetically fixed. For example, several differences in human social behavior result instead from sociocultural or economic constraints on women. Since gregarious animals use ornamentation for various social functions, perhaps some of their sex differences are, similarly to human behavior, due to social coercion or ecological constraint (their closest equivalents to human social and economic constraints, respectively). We found sex differences in ornamentation that disappear plastically in a social species with conventional sex roles. The red bill of common waxbills (Estrilda astrild) is on average more saturated in males, but in our experiment female bill color correlated with night temperature, an important energetic stressor, suggesting that sexual dichromatism disappears when ecological conditions are favorable to females. Female ornamentation may be more adversely affected by ecology because of their life history that requires balancing investment in ornamentation with maintaining reproductive condition. Manipulation of stress-related physiology (ACTH challenge) suggests that this effect was not mediated by stress mechanisms. Social coercion appears to not explain sexual dichromatism: males were not more aggressive than females, aggressiveness was not related to bill color, and manipulation of reproductive axis’ physiology (GnRH challenge, which in many species mediates aggressiveness) did not increase bill color. Our results show parallels to the plastic sex differences of humans in social animals and suggest that studying their ecological vs. social causes provides a biological backdrop for understanding the human case as well. Many sex differences in human social behavior result from economic or sociocultural constraints on women, while sex differences in the ornamentation of animals with conventional sex roles are thought largely genetically fixed. We show that a sex difference in ornamentation—the redder bills of male than female common waxbills—disappears plastically in an animal with conventional sex roles due to, in part, changes in female ornamentation. Social coercion did not explain reduced female ornamentation: aggressiveness did not predict bill color, and males were not dominant over females. Instead, female bill color was reduced during colder weather, perhaps because females under energetic stress need to balance investment in social ornamentation vs. maintaining reproductive condition. Similarly to humans, some sex differences of gregarious animals may be due to females requiring appropriate conditions to express their full social potential.

Long-Distance Love Affair, or How to Root for a Team That's Three Thousand Miles Away

Long-Distance Love Affair, or How to Root for a Team That's Three Thousand Miles Away Paul Hensler (bio) As a lifelong Connectican whose first baseball idol was Mickey Mantle, I was possessed of a fandom that wandered from the New York Yankees in early 1967, to Boston later that year when the Red Sox survived a four-team scramble to win the American League pennant—and almost capture the World Series—and then back to New York in 1969 when the Mets stunned the Baltimore Orioles in the fall classic. With three major league franchises in such close proximity to my hometown, there is a natural inclination for others to assume that one of them is my team of choice. However, when a baseball conversation prompts the question of which club I root for—a group currently titled the Los Angeles Angels—that answer elicits a follow-up query. "Oh, you're from California?" My reply can only be sufficient by way of what follows. After divulging that I've lived in Connecticut my entire life, I explain a number of factors that entered into my confounding selection that occurred in 1970, give or take a year. In the late 1960s, the California Angels—and we'll revisit that name in a bit—were a mediocre team, but their shortstop, Jim Fregosi, was one of the better players at his position, and his keystone partner, Bobby Knoop, wasn't too shabby either. The supporting cast, however, was only fair to middling, so the Angels were destined to be a .500 team. Yet they displayed one sartorial dash that was unique: an actual halo of white that was stitched into the caps they wore. The navy panels of the hats were augmented by a bright red bill, and the white interlocking "CA" at the front made this headgear pretty classy looking, so classy, in fact, that I commandeered a copy of The Sporting News, and got Mom write a check to accompany the coupon [End Page 99] to be sent to a sporting goods dealer—in Chicago, if memory serves—for an Angels cap. After the passage of requisite time, a shoebox-sized carton arrived in the mail, and my excitement was at a level akin to Christmas morning. I couldn't wait to open the package and proudly outfit my pate with my halo-crested cap. Imagine my reaction when I uncrated the contents and discovered that the much-awaited item, while remaining faithful to the color scheme, featured two crushing revisions. Missing was the "CA," its space now occupied by an elongated lower-case "a," but worst of all was the absence of the cherished halo once adorning the top. Well, the halo wasn't completely gone, but it had become miniaturized and placed at a jaunty angle as if to be hanging from the top left of the new "a." Crestfallen but still loyal, I soon after broke out a little bottle of white Testor's model paint and did my own retro-update of the original halo around the top, the new reality and authenticity be damned. With the cap now conforming to my stilted standard, it was time to embark on the business of root, root, rooting for my home team, though located on the other side of the country. In an era predating the arrival of the internet, this posed a serious challenge to finding out the scores of many games, especially those played at night in Anaheim. Our most important local newspaper printed morning and afternoon editions, but you could always count on the composite posting of results to look like this, from May 14, 1976: Boston 2, Milwaukee 1 Baltimore 6, New York 2 Cleveland 6, Detroit 3 Kansas City 7, Chicago 1 Minnesota at California, late Texas at Oakland, late If the game—any game, for that matter—wasn't completed by 11:00 p.m., press time for the morning paper, that result would receive the "late" designation, and if you could hold out for the afternoon newspaper, at least you had the opportunity to catch up on the score. But unless the Yankees or Red Sox were involved...

Subspecific variation in sperm morphology and performance in the Long-tailed Finch (Poephila acuticauda)

Evolutionary biology endeavours to explain biological diversity, and as such it is critical to develop an understanding of the adaptive and functional significance of trait variation. Spermatozoa exhibit remarkable levels of morphological diversification. However, our understanding of the evolutionary causes and functional significance of this variation is limited, especially at the intraspecific level. We quantified variation in sperm morphology and performance between two subspecies of Long-tailed Finch (Poephila acuticauda acuticauda and P. a. hecki), a small grassfinch found in tropical northern Australia. Despite a zone of secondary contact, these subspecies are maintained as two distinct forms: P. a. acuticauda occurs in the western part of the species’ range and has a yellow bill, while P. a. hecki exhibits a red bill and is found in the eastern part of the range. We found small, but significant differences in sperm size between these subspecies (P. a. acuticauda had longer and narrower sperm than P. a. hecki), which was surprising given the recent evolutionary origins of these two taxa (i.e. 0.3 million years ago). Additionally, both subspecies exhibited high values of between- and within-male variation in sperm morphology, though in the case of sperm midpiece length this variation was significantly lower in P. a. acuticauda relative to P. a. hecki. We suggest these observed differences in sperm morphology are the result of genetic drift and reflect historical processes associated with divergence between the eastern and western populations of these two subspecies. Finally, we discuss the potential implications of our findings for the process of population divergence and reproductive isolation.

Assortative Pairings in Diamond Firetails (Stagonopleura guttata) are not the Result of Mutual Mate Choice for an Ornament

Positive assortative mating occurs when individuals with similar phenotypes mate more frequently with each other than is expected by chance. In species in which both the males and females are ornamented, assortative pairings could arise from mutual mate choice on the same trait. We test this mechanism of mate choice and assortative pairing in the Diamond Firetail (Stagonopleura guttata), an Australian estrildid finch in which both sexes are ornamented with red bills, red rumps and white flank spots. We have previously shown sex differences in the degree of ornamentation as females have more flank spots than males. These white flank spots are used during sexual display, being fully displayed by courting males and by females when approaching a displaying male. Here, we experimentally test whether mutual mate preference is based on the number of flank spots. There was no evidence for a direct mutual preference for spot number. Given a choice of potential mates with a natural or experimentally manipulated number of flank spots, males preferred females with more spots, while female preference was not solely based on flank spots. Intriguingly, in both wild and captive Diamond Firetails, we found the number of flank spots in pairs was correlated suggesting a basis for positive assortative pairing. Nevertheless, we conclude that assortative pairing in Diamond Firetails is not due to mutual choice of mates based on the number of flank spots. We discuss different selection pathways for this trait in each sex.

Zebra finch females prefer males with redder bills independent of song rate—a meta-analysis

Male zebra finches display multiple secondary sexual traits such as song and red bill coloration. This color is dependent on carotenoids, which enhance immune function and are antioxidants. A red bill may thus function as an indicator signal. The zebra finch is extensively used in the study of carotenoid-dependent signaling. However, studies of female mate preferences for redder bills show mixed results. Here, we report a meta-analysis of mate-choice studies that reveals that female zebra finches do prefer males with redder bills (r = 0.61), except when there was reduced opportunity for imprinting or when bill color was experimentally manipulated, which both reduced preference for red bills to approximately zero. The latter may either be due to aspects of the experimental design or due to bill color being correlated with another trait such as song rate as was previously suggested. We show, however, in a separate meta-analysis on a different set of studies that the correlation between bill coloration and song rate (r = 0.14) was significantly lower than the r = 0.61 between bill color and attractiveness. We conclude, therefore, that the role of bill coloration in mate choice cannot be solely due to an association with song rate. Thus, we conclude that females do prefer males with redder bills when there was sufficient opportunity for sexual imprinting, but to what extent this is causally related to the bill color remains to be established.

Oil pollution increases plasma antioxidants but reduces coloration in a seabird

It has been suggested that condition-dependent signals may be a useful measure of environmental quality. In this study, we tested the hypothesis that oil pollution enhances oxidative stress and impairs expression of a carotenoid-based signal in a wild population of the yellow-legged gull (Larus michahellis). During the courtship period, a group of gulls were fed a supplementary diet containing heavy fuel oil from the Prestige oil spill and were compared with control gulls fed a similar supplementary diet without fuel oil. Blood levels of polycyclic aromatic hydrocarbons, the most toxic components of crude oils, were higher (30%) in the Prestige oil-fed gulls than in the control gulls. Plasma concentrations of vitamin E and carotenoids were also significantly higher in the Prestige oil-fed gulls (31 and 27%, respectively). Although, the plasma levels of lipid peroxidation markers were higher (13%) in gulls fed with Prestige oil than in the control gulls, these differences were not significant, possibly because of the small number of gulls analyzed. The red bill spot was significantly smaller (16%) in the oil-fed gulls than in the control individuals. This study provides the first experimental evidence that a carotenoid-based signal in a free-living seabird is affected by exposure to oil pollution and is hence indicative of environmental quality. Since the yellow-legged gull belongs to a complex of species widely distributed throughout the northern hemisphere, the method described may constitute a useful tool for evaluating sub-lethal effects of oil spills in seabirds.

Sublethal effects on seabirds after the Prestige oil-spill are mirrored in sexual signals

It has been suggested that sexual signals may be a useful measure of environmental quality as they represent the sum of environmental pressures on the animal. Accordingly, it has been proposed that carotenoid-based coloration may be especially valuable in monitoring and detecting the sublethal effects of toxic pollutants in the environment. Here, we evaluate whether the carotenoid-based coloration in the bill of adult yellow-legged gulls reflects oil-induced sublethal effects in breeding colonies affected by the Prestige oil spill. In 2004, we took blood samples from 27 adult birds at four insular breeding colonies located in the pathway of the Prestige oil spill. We measured the size of the red bill spot area and analysed plasma biochemical parameters indicative of sublethal effects of oil contamination in gulls, including glucose, total protein, creatinine, inorganic phosphorus, aspartate aminotransferase (AST) and gamma-glutamyl transferase. We showed that the size of their red bill spot area was positively related to body condition, while negatively related with AST levels, an enzyme that is commonly used as an indication of hepatic damage in birds. Hence, the present study provides support for the idea that carotenoid-based colour integuments may be a useful measure of environmental quality.

Multigene phylogeny and DNA barcoding indicate that the Sandwich tern complex ( Thalasseus sandvicensis, Laridae, Sternini) comprises two species

The crested terns are a group of six species of seabirds with a world-wide distribution closely allied to but larger than typical Sterna species. They are black-capped with elongated crest feathers and most have a bright yellow or orange to orange–red bill (Gochfeld and Burger, 1996). The taxonomic status of this group as a separate genus, Thalasseus, is gaining increasing acceptance following the publication of a molecular phylogeny demonstrating they form a strongly supported monophyletic clade (Bridge et al., 2005). One of the remaining taxonomic uncertainties in the Sternini is in the classification of the species complex of the Sandwich tern (Thalasseus sandvicensis), a taxon whose definition and limits have been controversial over the last century. Within this complex, there are three forms that have been classified either as subspecies or species. The most frequent treatment is to consider them as three subspecies: the Sandwich tern (T. s. sandvicensis) that breeds on the Atlantic and Mediterranean coasts of Europe, Cabot’s tern (T. s. acuflavidus) that breeds on the Atlantic coasts of North America and the Caribbean, and Cayenne tern (T. s. eurygnathus) that breeds on the Atlantic coast of South America from Argentina north to the Caribbean. The three races of Sandwich tern were originally described as distinct species (Baird et al., 1884), and due to their morphological and behavioral similarities were later suggested to be part of the same species complex (Baird et al., 1884; Junge and Voous, 1955), an issue that is still controversial (Gochfeld and Burger, 1996; Hayes, 2004). These taxa are morphologically very similar, with a few distinctions: the Sandwich tern is slightly larger with wider white margin on outer primaries, shorter bill and, paler upperparts (Olsen and Larsson, 1995). Cabot’s and Cayenne terns are virtually identical

Ornithology, evolution, and philosophy: the life and science of Ernst Mayr, 1904-2005

The young naturalist in Germany. Childhood and youth. The family. Birdwatching. The duck with a red bill. University student in Greifswald and Berlin. Friendships at school and university.- The budding scientist. PhD thesis and examination. The influence of teachers. Erwin Stresemann - teacher and friend. Assistant curator at the Museum of Natural History in Berlin. Expeditions to New Guinea and the Solomon Islands.- Ornithologist in New York. The New York years (1931 - 1953). Emigration to the United States and life in New York City. Curator of ornithology at the American Museum of Natural History. Ornithologist and zoogeographer. Birds of Oceania. Birds of Australia, the Malay Archipelago, and SE Asia. Descriptions of new species and subspecies of birds. Zoogeography.- Biological species and speciation - Mayr's first synthesis. A modern unified theory of evolution. Community architect.- Life in New York during World War II. New York City and Tenafly, New Jersey. Cold Spring Harbor (1943 - 1952). Citizenship.- Professor of Zoology at Harvard University. The Harvard years (1953 - 2005). Teaching and PhD students. Director of the Museum of Comparative Zoology. Evolutionary biology - Mayr's second synthesis. Overviews of evolutionary biology. Integrated gene complexes versus beanbag genetics. Animal Species and Evolution. Behavior and evolution. Particular topics of evolutionary biology.-Ernst Mayr - The man. Personality and general views. Health. The farm near Wilton, New Hampshire. Residence in Cambridge, Massachusetts. Advisor to the National Academy of Sciences and the NSF. National and international recognition.- Systematics and classification. Diversity. Classification. Zoological nomenclature.- History and philosophy of biology - Mayr's third synthesis. History of biology. Philosophy of biology.-

Availability of nonpigmentary antioxidant affects red coloration in gulls

Red, orange, and yellow carotenoid-based colorations displayed by fishes and birds may function as honest sexual signals of the bearer's quality. However, the mechanisms underlying the expression of these traits and the information they convey are still controversial. Because carotenoids are antioxidants and carotenoid-based pigmentation is bleached as a consequence of oxidative processes, it has been suggested that the pigmentation may signal antioxidant status. We tested this hypothesis in the yellow-legged gull (Larus michahellis), a seabird that exhibits a carotenoid-based red spot on the lower mandible. The availability of a nonpigmentary antioxidant (i.e., vitamin E) to the gulls was modified before egg laying by means of a supplementary feeding experiment. During the incubation period, breeding pairs were captured to assess the intensity of the color and the size of the red bill spots. We measured the plasma level of lipid peroxidation, total antioxidant capacity, and carotenoids. We found that males that received vitamin E supplements had larger red spot than control birds but that color intensity was not affected by the supplements. Moreover, we found that only those plasma carotenoids involved in the red coloration were affected by the antioxidant supplementation, suggesting an active mechanism to increase red coloration. Overall, our results provide experimental evidence for the hypothesis that carotenoid-based coloration reflects the bearer's antioxidant status in male gulls.

Carotenoid-based ornamentation as a dynamic but consistent individual trait

Carotenoid-based ornaments act as signals of quality in many animal species. In contrast to feathers, which are relatively stable structures, carotenoid-pigmented integuments (e.g. bills, lores, tarsi) can change colour rapidly and may better reflect changes in physiological condition. I studied the seasonal variations in plasma carotenoids in red-legged partridges (Alectoris rufa) kept on a constant diet and free of intestinal parasites. Furthermore, I analyzed whether seasonal changes in circulating carotenoids were mirrored by the carotenoid-based coloration of eye rings and bill of this species. Plasma carotenoids showed seasonal variation, with higher levels coinciding with the end of the mating and the start of the laying season. Eye ring pigmentation was related to plasma carotenoid levels, and changes in bill hue (but not changes in UV or red bill chroma) mirrored the variation in plasma carotenoids during the breeding season. Despite the seasonal variation, individual differences in eye ring pigmentation and bill hue, UV and red chroma were consistent throughout the breeding season. Similarly, individual differences in eye ring pigmentation and bill hue and red chroma remained consistent between consecutive years. These results suggest that carotenoid based integumentary colorations act as dynamic traits that accurately reflect the carotenoid-status of individuals, thus reliably indicating consistent differences in individual quality. Furthermore, variability in signal expression appears to have a relevant genetic/phenotypic basis independently of environmental conditions.

Plumage Characteristics and Return Rate of One-Year-Old tropical Roseate Terns

We report an unusually high return rate (16%) of one-year-old Roseate Terns (Sterna dougallii) to their natal colony on Aride Island, Seychelles, in 2005. Detailed accounts of these birds are provided in terms of timing of arrival, breeding status, and plumage characteristics, and compared with those of two other age classes (2-year-olds and 3 to 6 year-olds) in the same colony and with temperate populations. One-year-old individuals returned on average three weeks later than older birds and did not attempt to breed. Their immature plumage dress (‘portlandica phase’) differed from their one-year-old temperate counterparts, with most birds showing several characteristics of adults in full breeding plumage, such as red bill and red legs, long tail-streamers, and absence of a dark carpal bar. Contrary to expectations from temperate studies, nonbreeding two-year-old individuals did not retain any characteristic of the portlandica plumage, and were virtually inseparable from breeding adults. The ad hoc return rate of Roseate Tern one-year-olds found in this particular year is high compared to recapture/resighting data from colonies in temperate areas, but is comparable to observations made at other tropical (Caribbean) breeding colonies. Altogether, these findings suggest that tropical Roseate Terns are prone to return to their natal site earlier than their temperate counterparts, and show a more rapid acquisition of the adult plumage. This may be especially the case in years of good food supply conditions, since the 2005 event coincided with the two years (2004-2005) of highest marine productivity recorded in the vicinity of Aride Island over the 1997-2005 period.

Sexual maturity, factors affecting the breeding season and breeding in consecutive seasons in populations of overabundant Victorian koalas (Phascolarctos cinereus)

It is important to have knowledge of basic population parameters to understand how these vary geographically and temporally and how they contribute to population dynamics. This paper investigates three of these parameters in Victorian koala populations: sexual maturity, aspects of the breeding season, and the continuity of individuals’ breeding. The investigation was carried out in koalas of known-age in two free-living (Redbill Creek on French Island and Brisbane Ranges) and one semi-captive (the Koala Conservation Centre on Phillip Island) population as well as koalas of unknown age in four Victorian populations of overabundant koalas: Mt Eccles and Framlingham in south-west Victoria, French Island in Western Port and Snake Island in south Gippsland. At sexual maturity, female koalas had a mean age (±95% confidence interval) of 24.4 months (23.5–25.3 months), a mean head length of 125 mm (124–127 mm) and a mean body mass of 6.6 kg (6.3–6.8 kg). Only 7.4% of independent females (of unknown age) were carrying young when they weighed less than 6 kg. The breeding season was more restricted in the south-west populations. At Framlingham and Mt Eccles 85% and 91% of births, respectively, occurred between December and March. At Snake and French Islands only 46% and 53% of births, respectively, were recorded in the same period. In the Chlamydia-free population (Red Bill Creek) none of the koalas that were monitored stopped breeding and then resumed breeding in a subsequent season whereas many females from Chlamydia-infected populations (Brisbane Ranges and the Koala Conservation Centre) did so. This variation in reproductive patterns is likely to make an important contribution to the variation in the demography observed in different koala populations.