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This article explores the complexities and conflicting terminologies surrounding the study of avian moult. It discusses two main nomenclatures, the 'life-cycle' system and the Humphrey-Parkes or 'H-P' system, and argues for a standardized and globally applicable terminology based on scientific evidence. The text also delves into the different patterns of molting in bird species, such as preformative molt and simultaneous molt, and discusses the evolution of molting patterns in different bird groups. It concludes that molting patterns have evolved multiple times within the passerine group, with the simultaneous alternate molt being more common in migratory and resident species in harsh habitats. [Extracted from the article]

The presence of foraging bears in Arctic breeding bird colonies has been increasingly reported in the literature, and these may constitute disturbance events which cause incubating birds to leave their nest. Avian predators may associate with bears during such events, likely to capitalize on unattended nests in the presence of bears. Here, we estimated changes in daily nest attendance of lesser snow geese Anser caerulescens caerulescens in the presence of foraging bears, and estimated the association between foraging bears and avian predators. We predicted decreased nest attendance by geese on days with bears, and close associations between avian predators and bears. We monitored snow goose nests with cameras from 2013 to 2018 to assess nest attendance behaviours on days when bears were in the colony compared to control days without bears. When bears were present in colonies, we estimated the probability of avian predator occurrence compared to control periods. When controlling for day of incubation and camera placement types, we found no significant effects of bears on daily nest attendance behaviours of snow geese (n = 85). We found a significantly higher probability of observing avian predators when bears were present (0.72) compared to control periods without bears (0.11). We show that snow geese do not alter daily nest attendance in the presence of foraging bears, and suggest this is due to the presence of avian predators. [ABSTRACT FROM AUTHOR]

The conservation of migratory species poses significant challenges that may be countered by detailed knowledge about the sites used by migrants throughout the annual cycle. We present the first GPS‐tracking data on the migration of declining Caspian terns Hydroprogne caspia breeding in the Baltic Sea. For 39 Caspian terns from colonies along a latitudinal gradient from 57 to 65°N, we identified key migratory routes, stopovers and wintering areas. In autumn these seabirds migrated using coastal and freshwater stopovers along six routes to reach their wintering areas across the Sahel, the Nile River Basin and the southern Iberian Peninsula. In spring, adults returned to the breeding grounds in the Baltic using a time optimizing strategy by reducing time at stopover by 78%, whereas most subadults remained sedentary and some performed only partial return migrations. Of the stopover sites used in both seasons, 58% are protected and have a reported management plan. Conservation strategies in wintering areas, stopover sites that are not protected or had not been previously recognized, and the inclusion of the species in important migratory flyways across Europe and Africa will be important to prevent further population declines of a species that depends on aquatic habitats. [ABSTRACT FROM AUTHOR]

Trade‐offs between current and future reproduction are central to the evolution of life histories. Experiments that manipulate brood size provide an effective approach to investigating future costs of current reproduction. Most manipulative studies to date, however, have addressed only the short‐term effects of brood size manipulation. Our goal was to determine whether survival or breeding costs of reproduction in a long‐lived species manifest beyond the subsequent breeding season. To this end, we investigated long‐term survival and breeding effects of a multi‐year reproductive cost experiment conducted on black‐legged kittiwakes Rissa tridactyla, a long‐lived colonial nesting seabird. We used multi‐state capture–recapture modeling to assess hypotheses regarding the role of experimentally reduced breeding effort and other factors, including climate phase and colony size and productivity, on future survival and breeding probabilities during the 16‐yr period following the experiment. We found that forced nest failures had a positive effect on breeding probability over time, but had no effect on long‐term survival. This apparent canalization of survival suggests that adult survival is the most important parameter influencing fitness in this long‐lived species, and that adults should pay reproductive costs in ways that do not compromise this critical life history parameter. When declines in adult survival rate are observed, they may indicate populations of conservation concern. [ABSTRACT FROM AUTHOR]

Collecting information of ecological and behavioural processes often requires continuous field monitoring, however, reiterative human presence necessary to obtain monitoring data can disturb both the environment and the study species. An example of this phenomenon is the monitoring of the formation and dynamics of seabird colonies; one of the reasons for colony failure is disturbances caused by the presence of researchers or conservation managers during data collection. In this study, an unmanned aircraft system (UAS) was used throughout the breeding period to monitor the temporal and spatial dynamics of a black-headed gull colony in the interior of a difficult-to-access island. This methodology permitted weekly visits to the colony without disturbance, which allowed for the continuous collection of spatial and temporal data on the process of colony formation. We obtained detailed information about nesting success and its relation with the distance to the nearest incubating neighbour, as well as the colony boundary along breeding season. Thus, we successfully monitored the dynamics of a bird colony and identified factors affecting individual decision making in colony formation using a UAS. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Much effort has been devoted to identify ecological and life-history traits which facilitate urban colonization by wild avian species, but surprisingly little is known about the population-level mechanisms of urbanization processes. In general, two different patterns of urban colonization have been proposed: 1) the model of independent colonization predicts that birds colonize cities independently in different geographical regions; 2) the model of leapfrog colonization assumes a single colonization event, while additional urban populations are established from the initial urban populations. The aim of this paper was to determine the pattern of urban colonization in a common waterbird, the Eurasian coot Fulica atra. For this purpose, we analysed microsatellite variation in three pairs of urban and rural coot populations from central Poland. We found that a newly-established urban population was genetically more similar to neighbouring rural populations than to long-established urban populations, as indicated by the analysis of fixation index, genetic distance and Bayesian assignment of individuals to genetic clusters. These results are consistent with the model of independent colonization, where neighbouring rural populations are a source of individuals that colonize new urban areas. However, our analysis also showed significant differentiation between long-established urban populations and adjacent rural populations, suggesting that genetic connectivity between two types of habitat decreases with increasing time since urbanization. Our study shows high complexity of urbanization processes in wild animal populations, as well as it underpins utility of molecular tools in studying population-level mechanisms of urbanization. [ABSTRACT FROM AUTHOR]

Nesting is a critical yet hazardous life stage for many birds. For colonial-breeding birds, the conspicuousness of the colony to predators suggests immense pressure to select optimal colonial nesting sites. But what drives selection of those sites? As with solitary nesting birds, reducing access by predators may be the single most important factor. If so, knowledge of the predators involved and the attributes of different potential colony sites can allow us to predict the features that make a site especially safe. We examined the attributes of trees used by breeding colonies of metallic starlings Aplonis metallica in tropical Australia, and experimentally tested if those attributes prevented nest access by predatory snakes. Our surveys confirmed that tree choice by starling nesting colonies is highly non-random, with all colonies located in tall trees in rainforest clearings, with no low branches and smooth bark. Experimental tests demonstrated that the climbing ability of predatory snakes depends upon bark rugosity, and that colony access by snakes depends on tree attributes such as bark rugosity and canopy connectivity. Our study confirms that colonial-nesting starlings select colony sites that provide a safe refuge from predation. Intense predation pressure may have driven the evolution of stringent breeding habitat criteria in many other species of colonial-breeding birds. [ABSTRACT FROM AUTHOR]

Habitat selection in avian species is a hierarchical process driven by different factors acting at multiple scales. Habitat preferences and site fidelity are two main factors affecting how colonial birds choose their breeding locations. Although these two factors affect how colonial species choose their habitats, previous studies have only focused on one factor at a time to explain the distribution of species at regional scales. Here we used 28 yr of colony location data of herons and egrets around Ibaraki prefecture in Japan in order to analyze the relative importance of habitat preferences and colony site fidelity for selecting breeding locations. We used Landsat satellite images together with a ground survey-based map to create land-use maps for past years and determine the habitats surrounding the herons and egrets colonies. Combining the estimated colony site fidelity with the habitat data, we used a random forest algorithm to create habitat selection models, which allowed us to analyze the changes in the importance of those factors over the years. We found high levels of colony site fidelity for each year of study, with its relative importance as a predictor for explaining colony distribution increasing drastically in the most recent five years. The increase in collective site fidelity could have been caused by recent changes in the population size of grey herons Ardea cinerea, a key species for colony establishment. We observed a balance between habitat preferences and colony site fidelity: habitat preferences were a more powerful predictor of colony distribution until 2008, when colony site fidelity levels were lower. Considering changes in the relative importance of these factors can lead to a better understanding of the habitat selection process and help to analyze bird species' responses to environmental changes. [ABSTRACT FROM AUTHOR]

Islands provide refuges for populations of many species where they find safety from predators, but the introduction of predators frequently results in elimination or dramatic reductions in island-dwelling organisms. When predators are removed, re-colonization for some species occurs naturally, and inter-island phylogeographic relationships and current movement patterns can illuminate processes of colonization. We studied a case of re-colonization of common eiders Somateria mollissima following removal of introduced arctic foxes Vulpes lagopus in the Aleutian Archipelago, Alaska. We expected common eiders to resume nesting on islands cleared of foxes and to re-colonize from nearby islets, islands, and island groups. We thus expected common eiders to show limited genetic structure indicative of extensive mixing among island populations. Satellite telemetry was used to record current movement patterns of female common eiders from six islands across three island groups. We collected genetic data from these and other nesting common eiders at 14 microsatellite loci and the mitochondrial DNA control region to examine population genetic structure, historical fluctuations in population demography, and gene flow. Our results suggest recent interchange among islands. Analysis of microsatellite data supports satellite telemetry data of increased dispersal of common eiders to nearby areas and little between island groups. Although evidence from mtDNA is suggestive of female dispersal among island groups, gene flow is insufficient to account for recolonization and rapid population growth. Instead, near-by remnant populations of common eiders contributed substantially to population expansion, without which re-colonization would have likely occurred at a much lower rate. Genetic and morphometric data of common eiders within one island group two and three decades after re-colonization suggests reduced movement of eiders among islands and little movement between island groups after populations were re-established. We predict that re-colonization of an island group where all common eiders are extirpated could take decades. [ABSTRACT FROM AUTHOR]

When the northern fulmar expanded its northeast Atlantic breeding range from the two known colonies, Grimsey in northern Iceland and St Kilda in the Outer Hebrides, Scotland, about 350 yr ago, the geographical pattern of colonisation - initially the Faroes, then Scotland, followed by Ireland and southern Britain - led James Fisher to propose a sole Icelandic source for the colonists. However, previously-analysed mitochondrial DNA from contemporary samples indicated a St Kildan origin for at least some colonists. If Fisher's hypothesis is correct and Iceland and not St Kilda was the source population for all of the new colonies, the Icelandic signal should be stronger in museum samples collected 100 yr ago when St Kilda was populated by people who harvested large numbers of fulmars. Patterns of genetic, specifically, nucleotide, diversity suggest an Icelandic origin for the pre-1940 samples. St Kilda birds contained a number of closely related haplotypes whereas Grimsey, Iceland, the other putative source population, contained diverse haplotypes. These two patterns are indicative of a younger and older population, respectively. When both nuclear aldolase and mitochondrial control region sequence data from historical samples collected on the newly colonized islands were examined, they contained highly divergent haplotypes characteristic of Grimsey, not St Kilda. Comparison of mitochondrial data from samples collected in the early and late 20th century showed an interesting pattern of haplotype turnover on St Kilda. Prior to 1940 the haplotypes present on St Kilda were genetically similar to one another, yet haplotype sampling in the 1990s showed highly divergent haplotypes on the island. We propose that these new haplotypes are not the result of mutation, but immigration from other colonies in the North Atlantic. [ABSTRACT FROM AUTHOR]

Long-lived animals sometimes skip one or more breeding seasons; however, little is known about their movements and activities during such 'sabbatical' periods. Here we present novel data on year-round movements and activities of two male black-tailed gulls Larus crassirostris during a sabbatical year. We compare the data with those in a year when they bred and with those of two other breeding males. The year-round migration routes of two sabbatical males were consistent with those of the breeding males: they returned to the breeding area but did not visit the colony in the sabbatical year. They landed more frequently on water (a potential index of foraging effort) during the non-breeding autumn and winter prior to the sabbatical year than before breeding. Sabbatical gulls may forage more intensively to recover body condition immediately after breeding. [ABSTRACT FROM AUTHOR]

Central-place foraging seabirds alter the availability of their prey around colonies, forming a “halo” of reduced prey access that ultimately constrains population size. This has been indicated indirectly by an inverse correlation between colony size and reproductive success, numbers of conspecifics at other colonies within foraging range, foraging effort (i.e. trip duration), diet quality and colony growth rate. Although ultimately mediated by density dependence relative to food through intraspecific exploitative or interference competition, the proximate mechanism involved has yet to be elucidated. Herein, we show that Adélie penguin Pygoscelis adeliae colony size positively correlates to foraging trip duration and metabolic rate, that the metabolic rate while foraging may be approaching an energetic ceiling for birds at the largest colonies, and that total energy expended increases with trip duration although uncompensated by increased mass gain. We propose that a competition-induced reduction in prey availability results in higher energy expenditure for birds foraging in the halo around large colonies, and that to escape the halo a bird must increase its foraging distance. Ultimately, the total energetic cost of a trip determines the maximum successful trip distance, as on longer trips food acquired is used more for self maintenance than for chick provisioning. When the net cost of foraging trips becomes too high, with chicks receiving insufficient food, chick survival suffers and subsequent colony growth is limited. Though the existence of energetic studies of the same species at multiple colonies is rare, because foraging metabolic rate increases with colony size in at least two other seabird species, we suggest that an energetic constraint to colony size may generally apply to other seabirds. [ABSTRACT FROM AUTHOR]

Ornithologists interested in the drivers of nest success and brood parasitism benefit from the development of new analytical approaches. One example is the development of so-called “log exposure” models for analyzing nest success. However, analyses of brood parasitism data have not kept pace with developments in nest success analyses. The standard approach uses logistic regression which does not account for multiple parasitism events, nor does it prevent bias from using observed proportions of parasitized nests. Likewise, logistic regression analyses do not capture fine scale temporal variation in parasitism. At first glance, it might be tempting to apply log exposure models to parasitism data, but the process of parasitism is inherently different from the process of nest predation. We modeled daily parasitism rate as a Poisson process, which allowed us to correct potential biases in parasitism rate. We were also able to use our estimated parasitism rate to model parasitism risk as the probability of one or more parasitism events. We applied this model to red-winged blackbird Agelaius phoeniceus nesting colonies subject to parasitism by brown-headed cowbirds Molothrus ater. Our approach allowed us to model parasitism using a wider rage of covariates, especially functions of time. We found strong support for models combining temporal fluctuations in parasitism rate and nest-site characteristics. Similarly, we found that our annual predicted parasitism risk was lower on average than the risk estimated from observed parasitism levels. Our approach improves upon traditional logistic regression analyses and opens the door for more mechanistic modeling of the process of parasitism. [ABSTRACT FROM AUTHOR]

While the factors influencing reproduction and survival in colonial populations are relatively well studied, factors involved in dispersal and settlement decisions are not well understood. The present study investigated exchanges of great cormorants Phalacrocorax carbo sinensis among six breeding colonies over a 13-year period when the breeding population in Denmark increased from 2800 to 36 400 nests. We used a multistate capture-recapture model that combined multisite resightings and recoveries to examine simultaneously recruitment, natal dispersal, breeding dispersal and annual survival of first-year, immature and breeding great cormorants. Mean survival of first-year birds (0.50±0.09, range=0.42–0.66 among colonies) was lower than survival of breeders (0.90±0.06, range=0.81–0.97). Mean survival of immature birds over the study period was 0.87±0.08. Dispersal from a colony increased with decreasing mean brood size in the colony in both first-time and experienced breeders. The choice of the settlement colony in first-time breeders was affected by conditions in the natal colony and in the colonies prospected during the pre-breeding years. In particular, first-time breeders recruited to colonies where they could expect better breeding success. Experienced breeders relied mainly on cues present early in the season and on their own breeding experience to choose a new breeding colony. Newly established colonies resulted mainly from the immigration of first-time breeders originating from denser colonies. Dispersal was distance-dependent and first-time breeders dispersed longer distances than breeders. We suggest that the prospecting behaviour allows first-time breeders to recruit in nearby as well as more distant potential breeding colonies. Dispersing breeders preferred to settle in neighbouring colonies likely to benefit from their experience with foraging areas. We discuss the importance of these movements for growth and expansion of the breeding population. [ABSTRACT FROM AUTHOR]

Despite many decades of study, scientists cannot answer why colonial breeding has evolved. This paper shows that the evolution of colonial breeding cannot be sufficiently explained by the evolutionary conditions proposed in previous studies. Until now, studies have compared colonial breeding with only solitary non-territorial breeding (two-state comparison) and have discussed factors that facilitate evolution of the former. Here, I propose a new approach, a three-state comparison, which compares colonial breeding with not only solitary non-territorial breeding but also solitary territorial breeding. This three-state comparison indicates that (i) merely determining the factors that make colonial breeding advantageous over non-territorial solitary breeding is not sufficient to explain the evolution of colonial breeding, (ii) the disadvantages of solitary territorial breeding can promote the evolution of colonial breeding, and (iii) the evolution of colonial breeding is far more influenced by different selection pressures than has been predicted by previous studies. Thus, the three-state comparison provides a more precise description of the conditions that lead to the evolution of colonial breeding. [ABSTRACT FROM AUTHOR]