Breeding Biology of the Whiskered Auklet (Aethia pygmaea): Postnesting Period

This is the third paper on the breeding biology of the whiskered auklet on Buldyr' Island (Aleutian Islands) based on material collected in 1993. Unlike other alcid birds, both adult and young whiskered auklets returned to the colony the night after the end of the breeding season. From the end of July until the third ten-day period of August, the number of adult birds that returned to the island was at approximately the same level, and then decreased, while the number of young birds that returned to the islands markedly varied, and peaks were noted every 5–8 nights. Adult birds continued to visit all the nest habitats, but not all nest chambers were visited equally frequently. In the first and third ten-day periods of August, the auklets visited 61% and 19.8% of the nest chambers, respectively. It remains unclear whether they were their hosts, or other birds used their nests for the next year. The return of adult and young birds to the colony to sleep after the breeding season appears to be related to the settled mode of life of the whiskered auklet and its feeding near the islands in water perturbations caused by tidal currents.     

Molting and Seasonal Bill-Plate Shedding in the Whiskered Auklet (Aethia pygmaea)

Feather molting and bill-late shedding were studied because of the unique features of the whiskered auklet biology; i.e., they continue to visit the colony after departure of their young. Like other auklets, the whiskered auklets begin to molt during breeding and do not lose their capacity for flight. The molt pattern of different wing feathers is adaptive and allows new feathers to be protected (when they are soft and could be easily injured) by old or full-grown new feathers during flight or feeding (diving) due to the different timing of the molt of primary feathers and their coverts. The possibility of combining breeding with molt appears to be related to the feeding features of the species. The species that feed on abundant and highly aggregated plankton are able to molt during breeding. The pattern of bill-plate shedding in the whiskered auklet is similar to that in the crested auklet.     

Population differentiation in whiskered auklets Aethia pygmaea: do diurnal and nocturnal colonies differ in genetics,morphometry and acoustics?

Despite a great number of empirical studies, the mechanisms of population differentiation and the factors that influence this process, particularly in seabirds, remain insufficiently understood. Here we analyzed population structure in the whiskered auklet Aethia pygmaea, a previously poorly studied alcid species with unusual differentiation in colony attendance rhythms (i.e. diurnal in the Sea of Okhotsk vs nocturnal in the Bering Sea), and examined the influence of it on intraspecific differentiation. For this study, we analyzed morphometric measurements, acoustic variables, mitochondrial control region fragment and five microsatellite loci from nine whiskered auklet colonies spanning the breeding range. Previous research has shown a clinal morphometric variation in this species. We build on this analysis by adding auklets from more colonies, for the first time analyzing vocalizations from different colonies and genetic structure of this species. Our data supports a clinal variation in morphometric and acoustic characters with the largest size and the lowest call frequency in western birds, and the smallest size and highest call frequency in the east. We also found two mitochondrial lineages – whiskered auklets from colonies in the Sea of Okhotsk and the Commander Is. (Bering Sea) and from the Aleutian Is. (Bering Sea), that were presumably formed during Sangamonian interglacial period (115 000–130 000 years ago). Genetic clusters found did not reflect differences in colony attendance rhythms, suggesting that they were shaped by other factors (e.g. differences in predator pressure) and are unlikely to have participated in the formation of population structure. Colony fidelity, mobility of birds, proximity of foraging grounds and location of colonies in relation to seasonal ice pack, seem to be more likely determinants of population differentiation.     

Heterospecific mating preferences for a feather ornament in least auklets

Auklets (Alddae, Aethiini) include five species of small, sociallymonogamous, sexually monomorphic seabirds that display a varietyof feather and bare-part ornaments during the breeding season.Previous experimental work on two auklet species has demonstratedthat some ornaments are likely to be favored by sexual selectionbecause mutual male and female mating preferences benefit individualswith the most elaborate expression of these traits. In thisstudy we experimentally investigated whether naturally crestlessleast auklets Aethia pusilla have a maring preference for foreheadcrests similar to the most prominent ornament of two other species,crested A. cristatella and whiskered auklets A. pygmaea. Ourobjective was to investigate the function of this ornament asa species-recognition mechanism or as a product of one or moreof three proposed sexual selection models that address the originof elaborate traits and preferences. During the experiment,least auklets reacted to realistic models equipped with artificialforehead crests with approximately an order of magnitude morefrequent sexual displays and greater interest, consistent withthe idea that they have a mating preference for crests, eventhough they do not naturally express this ornament This heterospecificpreference also favored large crest size. These results refutethe possibility that least auklet forehead ornamentation alonedetermines species recognition at present Among models of sexualselection considered, the results are consistent with the sensoryexploitation model, although this could not be established unequivocallybecause a viability indicator or Fisherian mechanism could havebeen involved if least auklets had an ancestor with a foreheadcrest.     

Assessment of 17 new whiskered auklet (Aethia pygmaea) microsatellite loci in 42 seabirds identifies 5–15 polymorphic markers for each of nine Alcinae species

We isolated 17 microsatellite loci in the whiskered auklet (Aethia pygmaea) and tested them for amplification in 48 species from 13 seabird families (including 42 seabirds). Fifteen of these loci were also tested for polymorphism in 38 of the species, which included nine species of Alcinae (four auklets, Atlantic puffin, dovekie, razorbill and two murre species). On the average, nine loci were polymorphic per Alcinae species.     

Reproductive performance of little penguins Eudyptula minor in relation to year, age, pair-bond duration, breeding date and individual quality

We measured breeding performance of little penguins Eudyptula minor at Phillip Island, Victoria, Australia, during a 21-year period. All birds considered in this paper (n=307) were of known age (2–22 y) and sex, and most were of known, or closely-estimated, pair-bond status (1–8 mates per bird; pair-bond durations 1–13 y). Breeding dates and breeding performance varied markedly from year to year; measures of annual performance were not associated with early breeding. Measures of individual breeding performance (clutch-size, hatching success, chick masses and productivity) were related to early laying, parental age, and duration of pair-bond. Dependence of breeding performance on parental age was curvilinear, levelling off at about 8 y of age. Productivity declined significantly among birds older than 8 y; this decline was not due to events in the last year of breeding ("terminal illness"). Breeding performance increased with duration of pair-bond at least through y 5. Early breeding was significantly related to age and duration of pair-bond. Most of these relationships were stronger among males than among females, and many of them were not significant when females were considered alone. After controlling for other factors, breeding performance varied significantly among birds, but autocorrelations were low and limited to intervals of one year. Parental quality (defined for birds studied in six or more years as the individual bird term in a GLM for productivity controlling for other factors) was not correlated with lifespan or other demographic parameters, but high-quality birds were less prone to change mates and burrows than low-quality birds. We know of no previous study in which simultaneous effects of laying date, age and pair-bond duration on breeding performance were measured, while controlling for year, individual quality and terminal illness.     

Is the citrus-like plumage odorant of crested auklets (Aethia cristatella) a defense against lice?

Plumage odors may function as chemical defenses against ectoparasites in birds. We tested this hypothesis for crested auklets (Aethia cristatella), a species of colonial seabird that emits a very strong citrus-like odor from its plumage. This odorant contains known chemical repellents. We evaluated evidence for chemical defense in this species using two approaches. First, we exposed pigeon lice to the volatiles emitted by freshly plucked plumage and by whole specimens. Louse survivorship was compared between these treatments and two controls. Second, we compared louse abundance on crested auklets versus a closely related congener that nests in close association. Louse survivorship did not differ between crested auklet treatments and controls. Comparison of ectoparasite loads showed that crested auklets had significantly higher louse abundance than least auklets (A. pusilla), even after controlling for body size. Our results failed to support two expectations for chemical defense. Presence of the crested auklet plumage odorant in our experiments did not reduce louse life span. Presence of the aldehyde odorant in nature did not reduce louse abundance on crested auklets. Hence we conclude that the aldehyde odorant is not immediately lethal to lice at natural concentrations in plumage.     

A tangerine-scented social odour in a monogamous seabird

Social odours, conspecific chemical signals, have been demonstrated in every class of vertebrate except birds. The apparent absence is surprising, as every bird examined has a functional olfactory system and many produce odours. The crested auklet (Aethia cristatella), a monogamous seabird, exhibits a distinctive tangerine-like scent closely associated with courtship. Using T-maze experiments, we tested whether auklets preferred conspecific odours and whether they distinguished between different types of scent, two prerequisites of chemical communication. Crested auklets exhibited: (i) an attraction to conspecific feather odour; (ii) a preference for two chemical components of feather scent (cis-4-decenal and octanal), which we identified as seasonally elevated; and (iii) differential responses to odours, as indicated by a preference for auklet odour, an aversion to mammalian musk, but no significant response to banana essence (amyl acetate). Our results suggest that crested auklets detect plumage odour and preferentially orientate towards this stimulus. The striking and well-described courtship display that involves the scented neck region, the 'ruff sniff', provides a conspicuous behavioural mechanism for odour transmission and the potential for scent assessment during sexual selection. Although the importance and full social function of chemical signals are just beginning to be understood in birds, including crested auklets, social odours promise to reveal a largely unexplored and possibly widespread means of avian communication.     

Behavior of crested auklets (<Emphasis Type="Italic">Aethia cristatella</Emphasis>, Charadriiformes,Alcidae) in the breeding season: Visual and acoustic displays

The crested auklet, a highly social planktivorous bird species of the Northern Pacific, is an important component of marine ecosystems. Although visual and acoustic modalities play a major role in the communication of these birds, the available data on the repertoire of their vocal signals and postures are scarce and lack quantitative analysis. This study deals with visual and acoustic displays of crested auklets on their breeding grounds and the occurrence frequencies of certain forms of social behavior in male and female birds. The data were collected on Talan Island (the Sea of Okhotsk) in 1987–1991 and 2008. They show that the rate of contacts between birds is very high and sex-specific: on average, males initiate 1.13 contacts/min, compared to 0.65 contacts/min initiated by females. Directionality of ruff-sniff displays differs depending on the posture of the recipient bird. The duration of the trumpeting display in males depends on their social surroundings. However, the duration of either the trumpeting display or the mutual cackling display during courtship is independent of the behavioral context. Vocalization of crested auklets is characterized by two independent basic frequencies occurring either sequentially or simultaneously. The role of different communicative modalities in the behavior of the crested auklet is discussed.     

Inter- and intra-season stability of vocal individual signatures in a social seabird, the crested auklet

Vocal plasticity due to changes of social context is well documented in passerine birds. In other bird species, the impact of social environment changes on the whole vocal structure and on individual specific signatures remains largely unexplored. Here, we assessed inter- and intra-season stability of specific features of individual signatures in advertising calls of crested auklet (Aethia cristatella) males and tested the effects of pair mate and territory changes on the stability of the calls. The crested auklet is a highly social seabird of the North Pacific that breeds in dense colonies, and its individuals switch pair mates and territories with probability of 25–54%. During summer 2008–2010, we recorded 464 trumpet calls from 21 individually marked males and determined their pair mates and positions of their displaying places on a breeding colony of Talan Island, Sea of Okhotsk. We found that strong individual specific features of crested auklet trumpet calls stay stable not only during one season but also from year to year. However, we failed to find any effects of pair mate or territory changes on individual signatures of crested auklet trumpet calls. Our results suggest that crested auklets can potentially use their individually specific trumpet calls to form long-term social bonds both between pair mates and between neighbors; however, future experimental studies should test whether this is indeed the case.     

Age of first breeding, dispersal and survival of Red Kites Milvus milvus in Wales

Twenty-nine Red Kites, that were tagged as nestlings in Wales, bred for the first time at 2–7 years old (mean 3–6). A minimum of 41% of tagged young had entered the breeding population by the 7th year. Individuals moved up to 22 km between birthplace and breeding place and, having bred, most stayed in the same locality from year to year. No differences in these various respects were found between the sexes, though two long movements by territorial birds both involved females. Annual survival of adult breeders was estimated at around 95%.     

Size of ornament is negatively correlated with baseline corticosterone in males of a socially monogamous colonial seabird

The Goymann–Wingfield model predicts that glucocorticoid levels in social animals reflect the costs of acquiring and maintaining social status. The crested auklet is one of the few avian colonial species where a mutual ornament in males and females is used in both sexual and aggressive displays. Previous studies of the crested auklet support the notion that the crest ornament is a badge of status in this species. Here, we examined the relationship between the crest ornament size and the adrenocortical function in breeding crested auklets. Crest length was negatively correlated with corticosterone at baseline in males, but not in females. Baseline corticosterone in females (but not in males) was negatively correlated with body condition index. Although male and female crested auklets are monomorphic in their ornamental traits, our results suggest that the socially mediated physiological costs associated with status signaling may differ between the sexes.     

Space use by Great Lakes Piping Plovers during the breeding season

ABSTRACT.   Identifying and protecting breeding habitat for imperiled species requires an understanding of the spatial and temporal movements of breeding individuals. During the 2003 and 2004 breeding seasons, we examined space use by Piping Plovers ( Charadrius melodus ) in the federally endangered Great Lakes population. We used coordinate geometry to estimate home range sizes of individual birds and examined relationships between home range size and breeding stage (incubation versus chick rearing), year, sex, number of locations, minimum plover age, distance to the nearest nest, and human beach use (high, medium, or low). The mean size of home ranges of Piping Plovers that fledged at least one chick was 2.9 ± 0.5 (SE) ha (range = 0.4–11.2 ha), and the mean linear beach distance traversed was 475 ± 53 m (range = 130–1435 m). Individuals used 3 times more beach area and 1.5 times more shoreline distance in 2003 than in 2004. Females used smaller areas than males overall and during chick rearing. Home ranges were smallest on beaches with low public use, suggesting that human disturbance may cause greater movement by individual plovers and that larger protected areas may be warranted on beaches frequented by the public to minimize disturbance to breeding birds. Our results demonstrate that nesting Great Lakes Piping Plovers occupy relatively small ranges and, therefore, that even relatively small areas of suitable habitat can have a high conservation value for this endangered population. However, the total area of habitat used varied substantially among individuals, and this should be considered when protecting habitat for the species.     

Yolk carotenoids and stable isotopes reveal links among environment, foraging behavior and seabird breeding success

Nutrients that are limited in availability, such as carotenoids, are potentially involved in trade-offs between homeostasis and reproduction. Despite their importance, factors that affect the capacity of female birds to meet their carotenoid requirements are poorly understood. We used δ¹⁵N stable isotope analysis to relate foraging behavior to yolk carotenoid deposition in two seabirds, Cassin’s auklet (Ptychoramphus aleuticus) and rhinoceros auklet (Cerorhinca monocerata), during each of five years. As expected from their narrower trophic range, Cassin’s auklets produced yolks with fewer carotenoid types than did rhinoceros auklets (one vs. three). Cassin’s auklets also fed on a lower trophic level diet richer in carotenoids, yet had lower total yolk carotenoid levels, which suggests a role for species-specific adaptations for carotenoid uptake and utilization. Within both species, lower trophic-level feeding was linked to higher yolk carotenoid levels, but through different mechanisms. In Cassin’s auklets, it was due to a population-wide response to environmental variation: in warm-water years, all females fed at a low trophic level and produced carotenoid-rich yolks. In rhinoceros auklets, it was due to individual differences similarly expressed in all years: females fed across a wide trophic range, and those that fed at a low trophic level produced carotenoid-rich yolks. Rhinoceros auklets bred more successfully in years when their yolks were rich in carotenoids, probably due to a correlated response to stronger marine primary production. Our results are novel because they link avian yolk carotenoid deposition to behavioral and environmental variations.     

Rates and consequences of relaying in Cassin's auklets Ptychoramphus aleuticus and rhinoceros auklets Cerorhinca monocerata breeding in a seasonal environment

We removed first eggs from early‐laying females to measure rates and consequences of relaying in Cassin's auklets Ptychoramphus aleuticus and rhinoceros auklets Cerorhinca monocerata at Triangle Island, British Columbia, Canada. Based on egg size and composition, the investment that Cassin's auklets made in first eggs was very close to that predicted from adult body mass, whereas rhinoceros auklets invested more. In both species, a high percentage of females relaid (90% of Cassin's and 87% of rhinoceros auklets). Breeding success declined weakly with later laying among control Cassin's auklet pairs, but pairs that we induced to relay bred more successfully than naturally late pairs, and similar to values predicted from laying dates of their first eggs. Their chicks also fledged heavier and younger than late control chicks, and similar to values in early control chicks, but followed the population‐wide seasonal decline in wing length at fledging. Nestling diets were dominated by Neocalanus copepods until late in the season, a sign that feeding conditions remained favourable until late. In contrast, rhinoceros auklet pairs induced to relay followed the population‐wide seasonal decline in breeding success, which was driven by a decline in hatching success. Pacific sandlance Ammodytes hexapterus, thought to be a preferred prey species, virtually disappeared from nestling diets in mid‐to‐late season, yet there was no seasonal decline in fledging mass. However, chicks from replacement eggs followed the declines among control chicks in both age and wing length at fledging. Despite the female having produced a replacement egg, and despite delayed breeding, there appeared to be little immediate consequence associated with relaying for Cassin's auklets, except for a tendency for their chicks to fledge with short wings. Consequences were more marked in rhinoceros auklets (greatly reduced hatching success, and having their chicks fledge with short wings), and this may have been due to the large investment made in eggs, and/or to delayed breeding. Results of this study show that attributes of Cassin's and rhinoceros auklets that lay at different times in the season can be important in driving seasonal declines in breeding performance, as found in studies on other Alcidae. They also show how decisions taken during the egg stage can have variable yet potentially important implications for fitness, even in relatively long‐lived species that lay single‐egg clutches.     

Population dynamics of the bearded vulture Gypaetus barbatus in southern Africa

The essential features of mortality and survivorship of bearded vultures Gypaetus barbatus in southern Africa were deduced from age class plumage characteristics. The population consisted of about 204 adult pairs within a breeding range of about 35,000 sq km. Pairs bred every year and produced, on average, about 0·9 young per pair per year. Young birds made up about 37% of the population, subadults 3·5% and adults 60%. About 182 fledged young were recruited to the population each year. The proportion of young birds in the population in different areas was inversely related to the breeding density of adult birds (range 24–47%). Young bird mortality over the four years to subadult age was 87%, the survival rate of adults was 94% and the mean lifespan of birds surviving to adulthood was 21·4 years. This study demonstrates the need to understand the relationship between adult breeding density and young bird numbers in different parts of their range to accurately deduce population dynamics characteristics.     

Reproduction and survival of Glaucous Gulls breeding in an Arctic seabird colony

ABSTRACT.   Despite being widespread and easily observed, little is known about the life history of Glaucous Gulls ( Larus hyperboreus ). From 1984 to 2007, we examined their breeding biology and demography at Coats Island, Nunavut, Canada, where they nest alongside a colony of 30,000 pairs of Thick-billed Murres ( Uria lomvia ). The gulls fed mainly on murre eggs and chicks and by scavenging adult carcasses. The median age at first breeding was 5 yr, and the mean age was 4.8 ± 0.9 yr. Adult survival was estimated as 0.84 ± 0.03 (SE). The mean clutch size was 2.56 eggs and the mean number of young reared per year was 1.6 (range = 0.9–2.2). Birds reared at the colony provided 40% of recruits. Assuming that survival of locally reared chicks that emigrated was similar to that of chicks that returned to the colony, about 22% of the young gulls survived to breeding age. The timing of breeding by Glaucous Gulls appeared related to the timing of laying by murres. Although the demographic characteristics of Glaucous Gulls in our study were similar to those of populations of other large gulls, adult survival was at the lower end of the range for populations of large Larus gulls. There is some evidence that Glaucous Gulls exhibit lower survival than large gulls breeding in temperate areas, possibly because of contaminant burdens. In general, however, the demographic characteristics of large gulls show little variation and are probably a product of their common phylogeny.     

American Kestrel reproduction: evidence for the selection hypothesis and the role of dispersal

Many hypotheses attempt to explain why younger, less experienced birds have a relatively low reproductive output. We evaluated reproductive patterns of marked American Kestrels Falco sparverius nesting in boxes in southwestern Idaho from 1992 to 2006 to test predictions of these hypotheses. Results were consistent with the selection (differential mortality) hypothesis and did not support the constraint, restraint or recruitment hypotheses. Most known-age Kestrels nested in their first year of life, and there was no apparent short-term or long-term reproductive advantage to delayed breeding. The number of years that Kestrels nested in study area boxes ranged from 1 to 6 years, with most Kestrels nesting in only 1 year. Reproductive rates were higher for birds with at least 1 year of nesting experience than for birds nesting in boxes for the first time. After 2 years of nesting, reproductive rates levelled off; there was no evidence for additional improvement or for senescence. Differences in reproductive output with experience/age were due to variation among and not within individuals. Individuals that nested in more than 1 year had similar reproductive rates in their first and second years. Poor producers either died or dispersed after 1 year of nesting in study area boxes. Successful females that nested early in the season and successful males that had been produced locally had the highest probability of returning to nest in a subsequent year.     

The effect of age and year on the survival of breeding adult Great Skuas Catharacta skua in Shetland

The survival rates of breeding adult Great Skuas Catharacta skua were examined at Foula, the largest colony in the world, where numbers have been declining since the late 1970s. Resightings of colour-ringed breeding adults over a 12-year period were analysed using Cormack-Jolly Seber models to estimate survival rates. Annual survival rates averaged 0.89 but varied among years between 0.82 and 0.93, with annual variations being temporally associated with variations in sandeel abundance during the breeding season. Most birds appeared to die outside the breeding season and so it is possible that nutritional stress and reproductive costs of breeding in years of poor food supply affect survivorship on migration or in the wintering range. Survival rates of adult Great Skuas were affected by their age according to a quadratic equation, with survival increasing significantly with age from 0.73 in 5-year-old-birds to between 0.85 and 0.96 in birds from 7 to 22 years old, with a sharp decline to between 0.75 and 0.87 in birds over 22 years old. Year effects were evident when controlling for age, indicating that annual variations in survival rates are not explained by changes in age-composition of the marked population among years.     

Sex-biased survival and breeding dispersal probability in a patchy population of the Rock Sparrow Petronia petronia

Demographic parameters of the polygynous Rock Sparrow Petronia petronia were investigated in a small patchy population in the Italian Alps. The population included two distinct breeding patches that differed in altitude and breeding success. Survival parameters were estimated by capture–recapture analysis of 170 individually marked animals. At the whole population level (Cormack–Jolly Seber model), no sex difference in local survival probability was detected. We then used a multisite capture–recapture approach (Arnason–Schwarz model) to investigate patch-specific survival probability and between-patch dispersal rate conditional on survival. Female local survival in the higher-altitude patch (mean ± se: 0.54 ± 0.04) was significantly greater than in the other patch (0.37 ± 0.04), probably because permanent emigration from the study area was greater. In the higher-altitude patch, breeding dispersal was constrained by the altitude limit and breeding movements were directed toward the patch at lower altitude. The probability of changing patch in the next breeding season was significantly higher for females (range 0.16–0.21) than for males (0.01–0.03). Breeding success varied between years and patches, being lower in the patch where frequency of polygamy and female local mortality were higher.