Journal of Ornithology最新文献

One of the most critical functions of nests in parids is thermal insulation, particularly during egg incubation by females and during the first week of the hatchlings’ life when they are poikilothermic. Several avian studies reported associations between aspects of breeding success and nest parameters. In this study, we present results regarding long-term (eleven breeding seasons) impact of nest parameters on breeding characteristics in Great Tits (Parus major) and Eurasian Blue Tits (Cyanistes caeruleus) in a deciduous forest and an urban parkland study area. Our findings indicate that in Great Tits and Eurasian Blue Tits the number of fledglings (and in Eurasian Blue Tits also clutch size tended to be) was positively associated with lining mass and was influenced by the study area, with higher values observed in the forest. Additionally, there was a relationship between lining mass and higher hatching success in both tit species. We also demonstrated that both clutch size and number of fledglings were higher in Great Tits in the forest and in Eurasian Blue Tits the number of fledglings was higher in the forest. The study site also impacted hatching success, with Great Tits showing higher rates in the forest, and fledging success for Eurasian Blue Tits being higher in the forest. The number of fledglings differed between years in Great Tits and hatching success and fledging success differed between years in both Great and Eurasian Blue Tit species. We conclude that avian nests play an important role during reproduction, and the materials used to construct nests contribute to various functional properties. However, further studies are needed to establish clear relationships between nest parameters and breeding performance.

The association between migratory strategies and life-history traits helps explain how migratory organisms balance the energetic costs and survival risks with the benefits of migration. However, there is no consensus on how life-history traits associate with migration, and on migrant’s position at the slow–fast continuum of life history. Birds subject to different selective pressures are likely to show distinct patterns from each other. We used data from egg collections to investigate the relationship between reproduction and migration by assessing clutch size and egg size of 58 migratory and non-migratory tyrant flycatchers breeding in South America. We first compared clutch size and egg size of migrants and non-migrants, and then we assessed how migrants balance these reproductive traits with migration distance. Despite energy expenditure faced by migrants during their journey, migratory behavior was not a factor influencing clutch size and egg size of migrants and non-migrants. On the other hand, migration distance positively correlated with clutch size in migrants. Our study provides evidence that migration distance may constrain migrants in terms of costs and pressure reproduction in the direction of a faster life-history strategy, while migratory behavior per se may not be a determinant to place migrants in the slow–fast continuum of life history. Thus, among tyrant flycatchers breeding in South America variation in migratory strategies might be more important than migratory behavior in interacting with life-history traits. This study also demonstrates the potential of museum egg collections to test ecological hypotheses that investigate large-scale variation in breeding parameters of birds.

We analysed the migratory behaviour of adult Northern Gannets (Morus bassanus) breeding at Helgoland in the North Sea, based on data obtained from geolocation devices in the non-breeding season 2016–2017. Birds moved east and south-west to a broad range of wintering sites, ranging from the western Baltic Sea to North-West Africa. Three out of 12 birds spent the winter in Africa, while 9 birds wintered in Europe, with the primary wintering sites in the North Sea. All but one tagged bird spent some time in the Baltic Sea or in the transitional waters between the North Sea and Baltic Sea. We also analysed data from online databases (dofbasen.dk, ornitho.de) and the German Seabirds at Sea database to explore the extent to which Northern Gannets used the western Baltic Sea, as well as the Kattegat and Skagerrak, during the winter months. Records of Northern Gannets in Danish waters have increased substantially over the last 18 winters, with particular increases in the Baltic Sea. There was also a notable increase in sightings of Northern Gannets in German Baltic Sea waters, but this occurred later than in the more northerly Danish waters. Both analyses demonstrated that Northern Gannets explored the western part of the Baltic Sea, as well as the Kattegat and Skagerrak, increasingly intensively. This recent increase in sightings is in accord with the establishment and exponential increase in the nearest breeding colony of Northern Gannets at Helgoland.

Among territorial birds, the number of conspecific neighbours sets the social context of communication. There have been many investigations of vocal behaviour and its important role in territory defense and mate attraction in birds; however, the effect of the density of conspecific neighbours on avian communication has received little attention. In this study, we reviewed the literature on the influence of local density on vocal communication in birds, exploring how the number of conspecific neighbours influences avian vocal behaviour, by conducting a literature review following the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) in two databases: Web of Science and Scopus. We also included additional articles from a more flexible search in Google Scholar. We found 19 studies of birds that included data on vocal behaviour in relation to the number of conspecific neighbours. The majority of these studies (14 of 19) showed that local density influences avian vocal behaviour. Overall, these studies revealed an effect of local density of conspecifics on song rate (expressed as song rate, syllable rate, solo song rate, or singing rate). Other vocal behaviours that were shown to vary with local density included song-type switching, song duration, peak frequency, and song variation. Most studies focused on temperate-zone species where males are the predominant singers. Our results reveal a bias towards the study of male songs in the context of local density, with very few studies on female song; this corresponds with a historical geographical focus on temperate birds. We present experimental design suggestions for future investigations, including predictions for males and females of tropical and temperate species. Finally, we argue that more research on this topic is needed, and that investigations of vocal communication will benefit from further study of the influence of density on avian vocal behaviour.

Climate change is a key driver of biodiversity loss in multiple ecosystems, which can act at multiple stages of a species life- and annual cycle. Identifying where, when, and how these impacts may happen is key to understanding, and planning for, the population-level effects of climate change. This study assesses how climate change will impact the breeding and non-breeding areas of the European Bee-eater Merops apiaster, a long-distance migratory bird, by combining correlative species distribution models with recent tracking data to account for population connectivity between breeding and non-breeding sites. The three populations studied (Iberian, German, and Bulgarian) demonstrated different levels of exposure to climate change, as well as different patterns of connectivity. The Iberian breeding population showed high exposure to climate change in both its breeding and non-breeding sites, which may result in significant, interacting impacts on this population. In contrast, breeding populations in Germany are likely to benefit from climate change, both in their breeding and non-breeding range. Connectivity also varied; while most populations demonstrated extremely high connectivity between breeding and non-breeding sites, the Iberian population was substantially more behaviourally flexible, indicating there may be some adaptive capacity of this population to change non-breeding sites if some become less suitable due to climate change. Incorporating breeding and non-breeding areas into species distribution modelling highlights how the impacts of climate change may combine into multiplicative impacts across a species’ annual cycle, and how combining methodologies and data sources can provide greater insight into the impact of climate change on migratory species and, in turn, inform conservation action.

Collecting empirical data is essential for understanding the ecology and biology of a species. If the data collection procedure includes direct interaction with the study subject, particularly regarding repeated measures, there may be a risk of introducing biases on the collected dataset due to changes in the behaviour and/or physiology of the studied individuals. This can be particularly relevant during the breeding season when disturbance by researchers can affect birds on various aspects, including nest and chick survival, physiology, and chick body condition. Researcher effects on the chicks’ body condition have been shown in some species, but were apparently absent in others. Here, we investigate whether varying levels of handling influences the body condition of Eurasian whimbrel (Numenius phaeopus) chicks, using data collected on 88 individuals handled up to 11 times, during two breeding seasons. We found that neither the handling event (ordinal occasion when a chick was handled) nor the handling interval (period between two consecutive handling events) affected the chick’s body condition, but we found evidence that body condition is individually consistent during development. Hence, the levels of handling in our study did not have an apparent effect on Eurasian whimbrel chicks’ body condition. Although other potential effects may arise via researchers’ disturbance, our findings contribute to the discussion on researchers’ impacts on their study subjects, emphasizing the importance of species-specific evaluations to improve research methodologies and ethical practices.

The present study provides data on clutches with dwarf eggs from a large sampling in a colony of Yellow-legged Gulls (Larus michahellis) over 31 years. Their occurrence was very low, with a global percentage of 0.26%. Significant variations were not detected among periods of 10 or 11 years. In all the cases, only one dwarf egg was found per clutch. Mean volume of dwarf eggs was 34% of that of non-dwarf eggs. Their content was mostly albumen and a very reduced quantity of yolk, and they were infertile. Several results of the study (the laying order of the dwarf eggs, their mean clutch size and the mean size of the non-dwarf eggs from clutches with dwarf eggs) support the hypotheses that runt eggs occur from a temporary disturbance to the reproductive tract.

An equal sex ratio at the population level is the usual, evolutionarily stable condition. However, at the individual level, it may be adaptive for parents to manipulate the sex of their offspring, especially in species with sexual size dimorphism (SSD) when the costs and benefits of producing sons and daughters can vary. In this study, we investigated the hatching sex ratio (HSR) and fledging sex ratio (FSR) in the Whiskered Tern (Chlidonias hybrida). Despite the fact that SSD exists in Whiskered Terns already at the chick stage, HSR and FSR did not deviate from parity at the population level. We tested the dependence of HSR, FSR and the survival probability of males and females on the individual hatching date, average egg volume (in a clutch) and the number of nestlings. None of these factors influenced HSR. Survival probability was negatively correlated with the number of hatchlings. The proportion of females among the fledglings was positively correlated with the average egg volume per clutch. To better explore the effect of egg volume on the sex ratio, we tested the relationship between exact egg volume and hatchling sex or hatching success at the individual level; but despite the quite large sample size, our analyses failed to reveal any relationship. The sex ratio was equal among chicks that were found dead in a nest, mostly due to starvation, but more female than male chicks disappeared from nests (mostly due to predation), primarily in the first week of life. This indicates that females may be easier to predate, very likely by frogs hunting small chicks.

Sexing bird species with monomorphic plumage is generally challenging, and sexual size dimorphism (SSD) is often used to develop morphometric-based sexing tools, e.g., using discriminant functions. Within species, local selection pressures, age-related and season-related growth may, however, induce geographical and temporal variations in body size and SSD. Such variations may complicate the development of reliable morphometric-based sexing methods at a broad scale. We first investigated body size variations in a migratory shorebird species with wide breeding and wintering ranges, the Sanderling Calidris alba, within the two breeding populations (Greenland and Russia) and three staging/wintering populations (United Kingdom, Iceland and Mauritania), which belong to the same flyway. Then, for samples from each region, we tested whether site-specific (i.e., “regional”) functions performed better than functions developed for birds from the other sites (i.e., “foreign” functions) or than an overall (“flyway”) function that combined all sampled individuals. We found minor variations in SSD between regions, but significant differences in body size between sexes and regions. Females were larger than males and, for instance, breeders had longer wings than staging and wintering birds. Regional functions had similar sexing efficiency as any other functions applied to sample from each region, except for Western Africa where the regional function performed slightly better than some of the other functions. Furthermore, the flyway function developed after merging all subsamples had a similar efficiency than the regional functions, i.e., from 75.4% to 90% of correct sex assignment depending on the region. Given the small or lack of benefit in using regional functions, we conclude that the flyway function can be used reliably to sex Sanderlings measured at different sites, years or seasons within the East Atlantic flyway. Our results may help to develop global sexing function for other bird species.

Eurasian Jays (Garrulus glandarius) typically store seeds on the ground in shallow caches, promoting tree recruitment. However, speculation exists that Eurasian Jays occasionally store a portion of seeds in microhabitats unsuitable for proper germination. Here, we report that unexpected caching sites in Eurasian Jays can be much more widespread than previously considered and despite their accidental character it seems to be a durable aspect of Eurasian Jay’s hoarding behavior. Out of 259 removed acorns of Pedunculate Oak (Quercus robur), we localized 31 consumed and 222 stored acorns. Six experimental acorns (3% of stored acorns) were found stored by jays in unexpected caching sites: (i) above the ground on individuals of Scots Pine (Pinus sylvestris), (ii) inside the woody stems of Reynoutria sp. individuals, (iii) in a rotten trunk, and (iv) among ruin debris. Our findings suggest the need to revise our understanding of so-called unexpected caching in Eurasian Jays. This highlights a previously overlooked aspect of oak-jay interactions, offering a valuable piece to the puzzle.