Journal of Ornithology最新文献

Avian visual fields have been predicted to be highly conserved at the intraspecific level and be repeatable within an individual, yet this has never been previously determined empirically. Typically, only 2–3 individuals of a species are measured during visual field procedures, and these individuals are measured just once. Using the ophthalmoscopic technique, we measured the visual fields of five Homing Pigeons (Columba livia) over time to assess the repeatability at both the individual and population levels. Using a series of repeatability estimates, we found that visual field measurements were highly repeatable at the individual level, and moderately repeatable at the population levels; visual fields are statistically consistently similar between individuals of the same species and over repeated measures of the same individual. We conclude the ophthalmoscopic technique is a repeatable measure of the visual fields of an individual, and small numbers of individuals are moderately representative of the species. Still, caution should be applied when looking at certain elevations, and higher sample sizes should be used when and where available.

There are many environmental, life-history, and physiological predictors of disease in animals, but we need more studies that examine multiple factors simultaneously to better understand comparative risks of infection in wildlife. The House Finch (Haemorhous mexicanus) is a North American songbird that has served as a model ecological system for assessing avian disease predictors and responses. Among its various diseases is coccidiosis, an intestinal parasitic infection that is more common in urban finches and in males with drab plumage. Here, we examined additional nutritional–physiological predictors of coccidiosis presence and severity in House Finches, with an emphasis on plasma concentrations of lipid-soluble vitamins (retinol, or vitamin A; tocopherol, or vitamin E) as well as blood glucose and ketones. We found that plasma retinol concentration significantly predicted the presence of coccidiosis; coccidia-infected finches had lower levels of retinol than those without coccidiosis. We also found an effect of the sex*retinol level interaction on coccidiosis severity; retinol levels were lower in more-infected females, but no such pattern was found in males. Overall, we demonstrate a unique link between retinol and intestinal disease status in a wild bird species; to date, such a relationship had only been uncovered in domestic chickens. Mechanistically it is possible that, due to the antioxidant and immunosupportive properties of retinol, animals deficient in retinol are more susceptible to coccidial infections, or that, as in poultry, infection directly lowers retinol levels; experimental manipulations are needed to disentangle these possibilities and to understand why the negative relationship between retinol and coccidiosis severity exists in females but not males.

The most important cause of the declining numbers of wading birds is a combination of habitat loss and degradation, as well as low productivity due to predation. Knowledge of the habitat requirements of this endangered group of species is critical for maintaining and restoring suitable breeding habitats. The aim of this paper is to characterize those habitat components of the Eurasian Curlew (Numenius arquata) which determine its choice of nesting site. This study was undertaken in three sites in Poland, the most important breeding areas of this species in this country. Our results showed that macrohabitat factors affect curlew nest-site selection in different ways. The most important ones were distance to a forest edge, the percentage cover of managed farmland in the vicinity and the number of farmland plots close to the nest. Other habitat components, such as distance to scattered trees, distance to roads and soil category, were of lesser importance and could be treated as localized. This study is a contribution to the knowledge of the Eurasian Curlew’s nest-site selection in farmland grasslands, which may have implications for its conservation.

Benefits gained from participating in mixed-species bird flocks include improved foraging efficiency and reduced predation risk. However, distinguishing between these two benefits in the wild is challenging. To investigate this problem, we observed flocking behavior of attendant species and measured the heterospecific preference of association to their nearest neighbors, especially to the dominant nuclear species, Grey-cheeked Fulvetta (Alcippe morrisonia), in a subtropical forest of Taiwan. We found that different foraging guilds of attendant species exhibited significantly different heterospecific preferences of association in mixed flocks. Based on these preferences, we identified at least three different types of attendant species in terms of benefits gained. Two aerial foraging canopy species actively associated with foliage/perch gleaners (thus demonstrating high heterospecific preference) to catch flushed prey, consequently gaining direct foraging benefits. Three understory species and a woodpecker species followed at a distance behind the flock (thus demonstrating low heterospecific preference) to predominantly gain anti-predation benefits, because they could still eavesdrop on heterospecific alarm calls. Two regular attendant species, White-bellied Erpornis (Erpornis zantholeuca) and Rufous-capped Babbler (Cyanoderma ruficeps), likely gained both foraging and anti-predation benefits, because they stayed very close to the nuclear species for a long period of time. Our results suggest that attendant species that forage mainly on surface prey usually have higher heterospecific preferences of association in order to maintain activity matching and direct foraging benefits. On the other hand, attendant species that mainly exploit concealed prey have lower heterospecific preferences of association and primarily derive anti-predation benefits even when they are at a distance from the moving flock.

This study examines the bird fossils unearthed from the natural tank deposits of the João Cativo Paleontological Site (JCPS), nestled in Itapipoca, Ceará State, Brazil. These deposits, a cornerstone in our understanding of the paleoecology of the Brazilian Intertropical Region during the Quaternary period, have conserved a staggering diversity of fauna, notably the Quaternary megafauna. In addition to the megafauna, the JCPS natural tanks have safeguarded unidentified bird fossil remains. Our research uncovers the presence of birds from the Accipitridae family, a group with a broad distribution across the American continent, and the record of Rhea americana, a terrestrial bird that populates biomes such as Cerrado, Caatinga, and the Pampa grasslands. The existence of these fossils underscores the JCPS's pivotal role as an exceptionally diversified deposit, not only in mammals but also in birds and other animal groups.

Extra-pair paternity is common among socially monogamous bird species and considered an important driver of post-copulatory sexual selection on ejaculate traits including sperm traits. Patterns of extra-pair paternity and sperm size both show substantial variation among populations, yet we know little about the expression of these key reproductive traits at high latitudes. Here we report patterns of extra-pair paternity and describe variation in sperm dimensions in a Norwegian population of the socially monogamous Great Tit (Parus major) breeding beyond the polar circle at 69° northern latitude. Across six study years, we detected extra-pair paternity in 19.2% of 26 broods, and on average 4.7% of nestlings per brood were extra-pair offspring. As expected from results of previous intraspecific analyses of latitudinal variation in extra-pair paternity rates, the observed rate of extra-pair offspring was low in comparison to published estimates from more southern Great Tit populations (range: 2.9 − 20.4%). Our results therefore support a pattern of decreasing levels of extra-pair paternity with increasing latitude in this species also for extremely high latitudes. Overall mean sperm total length amounted to 97.5 ± 0.6 (SE) μm and 30.6% of the total phenotypic variation in sperm total length was explained by differences among sperm samples. The among-sample coefficient of variation in mean sperm total length per sample was 1.93%. Using previous comparative work as a yardstick, this value is substantially lower than expected for the observed frequency of 4.7% extra-pair offspring.

Body condition serves as a critical indicator not only of an individual’s overall health but also provides valuable insights into the strategies adopted by organisms in response to factors like resource availability, climate, and biological interactions. In this study, we dove into a comprehensive dataset sourced from the Atlantic Forest Biome, encompassing 4152 individuals spanning 114 bird species across 27 families and 8 orders. Here, we tested the macro-ecological determinants of body condition, assessed through the scaled mass index, a metric derived from body mass and length. Our analytical approach involved hypothesis testing, considering several factors as predictors, including forest cover, local species diversity, mean annual temperature, mean annual rainfall, and habitat breadth. We employed a phylogenetic generalized linear mixed model (PGLMM) to investigate the impact of these factors on body condition. Our findings reveal a negative association between habitat breadth and body condition, suggesting that habitat-specialist species might reap the rewards of enhanced resource predictability or wield a competitive edge over generalist species, thereby potentially elevating their body condition. Furthermore, we discovered an important association: individuals in habitats with higher local diversity exhibited lower levels of body condition. We discuss potential explanations for this, such as increased competition, heightened susceptibility to pathogens, or a higher vulnerability to diseases. Lastly, we found a positive association between mean annual rainfall and body condition, suggesting that potentially increased food and water availability in areas with greater rainfall could contribute to enhanced body condition. Our study highlights the crucial role of species interactions and habitat usage in influencing the body condition. These findings have significant implications for conservation strategies, offering insights that can guide targeted interventions in areas where bird populations show lower body condition, indicating potential vulnerability to disturbances.

The foraging ranges of breeding seabirds differ between species and colonies, depending on species locomotion traits, food availability, environmental characteristics, and social factors. The Common Tern (Sterna hirundo) is a generalist seabird that breeds and forages in a wide variety of habitats in both freshwater and marine environments. Using GPS loggers, we compared the foraging range, foraging patterns, and the colony attendance of Common Terns from freshwater and marine colonies during the incubation and chick-rearing periods. Common Terns from freshwater colonies foraged at lower distances from colonies and had higher daily colony attendance than conspecifics from marine colonies in the Adriatic Sea. Maximum distance to the colony and 50% and 95% utilisation distributions were higher during the chick-rearing phase. Colony attendance was higher during the incubation and among females. Compared to freshwater terns, marine birds foraged later in the evening. Freshwater terns mainly foraged along rivers but also visited smaller lakes. Terns from marine populations were not recorded to forage in freshwater sites within the foraging range. Tracking studies with finer temporal scale and detailed spatio-temporal data on wind and tide dynamics are needed to understand environmental factors affecting foraging dynamics of Common Terns in the Adriatic Sea.

Trace metals produced by anthropogenic activities in particular in urban environments, such as lead and zinc, can induce oxidative damage in exposed individuals. Therefore, trace metals could act as a selective pressure for higher resistance to oxidative damage by favoring individuals able to plastically produce antioxidants once exposed to metal to counterbalance the oxidative damage production. In this study, we experimentally challenge this hypothesis in 69 feral pigeons (Columba livia var. domestica) originating from an urban environment by exposing a subset of them to zinc (n = 18), lead (n = 17) or zinc and lead (n = 16) during 14 weeks to see if exposed individuals showed an increased anti-oxidant production compared to controls (n = 18). Our results reported that zinc exposure induced oxidative stress by increasing oxidative damage but failed to detect a compensatory production of antioxidants in exposed individuals. However, our results report lower oxidative damage for reproducing individuals, which is consistent with an oxidative shielding phenomenon occurring prior to reproduction in males to protect the sperm, and during egg-laying in females to protect offspring. In conclusion, our study does not support an adaptive antioxidative response in individuals exposed to trace metals, but it does partly support the oxidative shielding hypothesis.