Feather steroid hormone concentrations in relation to age, sex, and molting time in a long-distance migratory passerine

Effects of Heat Stress on the Laying Performance, Egg Quality, and Physiological Response of Laying Hens

As high temperature and relative humidity (RH) are the main environmental factors causing heat stress, the temperature-humidity index (THI) serves as an indicator of heat stress in livestock animals. This study aimed to determine the effects of heat stress on the laying performance, physiological responses, egg quality, and blood profile of laying hens by subjecting them to environmental conditions with varying THI levels (68-85) for 28 days. The indicators of laying performance, such as feed intake (-30%) and egg production rate (-11%), significantly decreased in the hens exposed to severe heat stress (33 °C, 66% RH) compared to those exposed to thermoneutral conditions (21 °C, 68% RH). Moreover, severe heat stress reduced the egg yolk color, eggshell thickness and strength, and Haugh units of the eggs produced by the laying hens. Furthermore, a significant increase in serum K+ and a decrease in Na+ levels were observed in the hens subjected to severe heat stress compared with those under thermoneutral conditions. Our results indicate that heat stress alters the physiological responses and metabolism of laying hens, resulting in a lower egg quality and production rate.

Time is of the essence: The importance of considering biological rhythms in an increasingly polluted world

Biological rhythms have a crucial role in shaping the biology and ecology of organisms. Light pollution is known to disrupt these rhythms, and evidence is emerging that chemical pollutants can cause similar disruption. Conversely, biological rhythms can influence the effects and toxicity of chemicals. Thus, by drawing insights from the extensive study of biological rhythms in biomedical and light pollution research, we can greatly improve our understanding of chemical pollution. This Essay advocates for the integration of biological rhythmicity into chemical pollution research to gain a more comprehensive understanding of how chemical pollutants affect wildlife and ecosystems. Despite historical barriers, recent experimental and technological advancements now facilitate the integration of biological rhythms into ecotoxicology, offering unprecedented, high-resolution data across spatiotemporal scales. Recognizing the importance of biological rhythms will be essential for understanding, predicting, and mitigating the complex ecological repercussions of chemical pollution.

Long term stability of corticosterone in feathers

Measuring corticosterone in feathers allows researchers to make long-term, retrospective assessments of physiology with non-invasive sampling. To date, there is little evidence that steroids degrade within the feather matrix, however this has yet to be determined from the same sample over many years. In 2009, we made a pool of European starling (Sturnus vulgaris) feathers that had been ground to a homogenous powder using a ball mill and stored on a laboratory bench. Over the past 14 years, a subset of this pooled sample has been assayed via radioimmunoassay (RIA) 19 times to quantify corticosterone. Despite high variability across time (though low variability within assays), there was no effect of time on measured feather corticosterone concentration. In contrast, two enzyme immunoassays (EIA) produced higher concentrations than the samples assayed with RIA, though this difference is likely due to different binding affinities of the antibodies used. The present study provides further support for researchers to use specimens stored long-term and from museums for feather corticosterone quantification, and likely applies to corticosteroid measurements in other keratinized tissues.

Chewing lice of passerine birds in reed beds in Slovakia, with a special focus on Panurus biarmicus

A total of 1185 passerine birds representing five species were examined for chewing lice in reed beds in southwestern Slovakia in spring (April) 2008, 2009 and 2016. Additional collecting focused only on chewing lice from Panurus biarmicus (Linnaeus, 1758) (Passeriformes: Panuridae) was carried out in spring (April), summer (July) and autumn (October) 2019. A total of 283 (24%) birds were parasitized by 10 species of chewing lice of four genera: Penenirmus, Menacanthus, Philopterus, and Brueelia. Most birds showed only very light (1-10 lice/host; 74%) to light infestations (11-20 lice/host; 16%). The authors found significantly higher prevalences and mean abundances of chewing lice on residents/short-distance migrants, that is, P. biarmicus, Acrocephalus melanopogon (Temminck, 1823) (Passeriformes: Acrocephalidae), than on long-distance migratory birds, that is, Acrocephalus scirpaceus (Hermann, 1804), Acrocephalus schoenobaenus (Linnaeus, 1758) (Passeriformes: Acrocephalidae), Locustella luscinioides (Savi, 1824) (Passeriformes: Locustellidae). No significant difference was found in the total mean intensity of chewing lice between these two groups of birds. Ischnoceran lice were more prevalent and abundant than amblyceran lice on residents and short-distance migrants, whereas the opposite was found on bird species that migrate long distances. A total of 146 (58%, n = 251) P. biarmicus were parasitized by 1490 chewing lice. Males of P. biarmicus showed higher prevalence and mean abundance than females with gradually descending values of prevalence, mean abundance and mean intensity from spring to autumn. The knowledge of the occurrence and population dynamics of lice on wild passerine birds can be useful in endangered species conservation programs and can also be applied to captive passerine birds, which may be analogous to resident birds in this sense.

Inter-annual repeatability and age-dependent changes in plasma testosterone levels in a longitudinally monitored free-living passerine bird

While seasonal trends in testosterone levels are known from cross-cohort studies, data on testosterone inter-annual individual repeatability in wild birds are rare. Also, our understanding of hormonal age-dependent changes in testosterone levels is limited. We assessed plasma testosterone levels in 105 samples originating from 49 repeatedly captured free-living great tits (Parus major) sampled during the nesting to investigate their relative long-term repeatability and within-individual changes. Furthermore, we examined the inter-annual repeatability of condition-related traits (carotenoid- and melanin-based plumage ornamentation, ptilochronological feather growth rate, body mass, and haematological heterophil/lymphocyte ratio) and their relationships to testosterone levels. We show that testosterone levels are inter-annually repeatable in females, with a non-significant pattern in males, both in absolute values and individual ranks (indicating the maintenance of relative status in a population). In males, we found a quadratic dependence of testosterone levels on age, with a peak in midlife. In contrast, female testosterone levels showed no age-dependent trends. The inter-annual repeatability of condition-related traits ranged from zero to moderate and was mostly unrelated to plasma testosterone concentrations. However, males with elevated testosterone had significantly higher carotenoid-pigmented yellow plumage brightness, a trait presumably involved in mating. Showing inter-annual repeatability in testosterone levels, this research opens the way to further understanding the causes of variation in condition-related traits. Based on a longitudinal dataset, this study demonstrates that male plasma testosterone undergoes age-related changes that may regulate resource allocation. Our results thus suggest that, unlike females, male birds undergo hormonal senescence similar to mammals.

Feather Corticosterone Measurements and Behavioral Observations in the Great White Pelican (Pelecanus onocrotalus) Living under Different Flight Restraint Conditions in German Zoos

The pinioning of birds was previously one of the most-accepted forms of mutilation in zoos. Despite a lack of knowledge on the effects of deflighting procedures with regard to the well-being of deflighted birds, pelicans are often reversibly deflighted by feather-clipping to keep them in open enclosures, including those with ponds without netting. In the present study, we focused on the welfare implications of flight restraint on one of the most commonly kept types of birds in German zoos, the great white pelican. A combination of behavioral observations and feather corticosterone concentrations (CORTf) of pelicans with different deflighting statuses (i.e., irreversibly deflighted, reversibly deflighted, and airworthy) was used to evaluate the effects of deflighting status on pelican welfare. We observed 215 individuals in 21 different German zoos. The pelicans lived in differently designed exhibits. An ethogram for these species was developed and their behavior was evaluated by scan sampling. Feather samples from 182 individuals were collected to determine if different deflighting conditions influenced the CORTf and therefore stress levels. The hypothesis was that the CORTf values of airworthy pelicans differ from those of deflighted pelicans. Tendencies with regard to the flight status groups were found. Conversely, reversibly deflighted pelicans had higher CORTf levels than irreversible deflighted and airworthy pelicans. Tendencies with regard to CORTf values and the group size of the kept pelicans were observed. The CORTf values were lower in groups consisting of more than 10 animals. In addition, the frequency of fluttering behavior was positively associated with CORTf values. Pelicans that frequently showed fluttering had higher CORTf values. Therefore, fluttering behavior might be considered a sign of stress levels in pelicans. This study is one of the first important steps in assessing the impact of deflighting procedures on the welfare of great white pelicans kept in zoos.

Early-Life Corticosterone Body Condition Influence Social Status and Survival in a Food-Caching Passerine

Individuals undergo profound changes throughout their early life as they grow and transition between life-history stages. As a result, the conditions that individuals experience during development can have both immediate and lasting effects on their physiology, behavior, and, ultimately, fitness. In a population of Canada jays in Algonquin Provincial Park, Ontario, Canada, we characterized the diet composition and physiological profile of young jays at three key time points during development (nestling, pre-fledge, and pre-dispersal) by quantifying stable-carbon (δ13C) and -nitrogen (δ15N) isotopes and corticosterone concentrations in feathers. We then investigated the downstream effects of early-life diet composition, feather corticosterone, and environmental conditions on a juvenile's social status, body condition, and probability of being observed in the fall following hatch. Across the three time points, the diet of Canada jay young was composed primarily of vertebrate tissue and human food with the proportion of these food items increasing as the jays neared dispersal. Feather corticosterone concentrations also shifted across the three time points, decreasing from nestling to pre-dispersal. Dominant juveniles had elevated corticosterone concentrations in their feathers grown pre-dispersal compared with subordinates. High body condition as nestlings was associated with high body condition as juveniles and an increased probability of being observed in the fall. Together, our results demonstrate that nestling physiology and body condition influence the social status and body condition once individuals are independent, with potential long-term consequences on survival and fitness.

Effects of feather processing methods on quantity of extracted corticosterone in broiler chickens

Corticosterone is known as a biological stress index in many species including birds. Feather corticosterone concentration (FCC) has increasingly been used as a measure for chronic stress status in broiler chickens. As sample preparation is the first step of analytical process, different techniques of feather matrix disruption need to be validated for obtaining better result in analysing corticosterone extraction. The current study was a validation of pulverizing the feather by bead beater (BB) and surgical scissors (SS) processing prior to corticosterone extraction in feather of broiler chickens. The type of feather processing prior to the hormone extraction may alter the final output. Thereby, finding a standard method according to laboratory facilities is pivotal. This study carried out to determine the effects of feather pulverization methods on the extraction amount of corticosterone in broiler chickens. Feathers were sampled from four weeks old Ross 308 broiler chickens (n = 12 birds). All broiler chickens were kept under the same environmental condition and had access to feed and water. Feather samples were assigned to one of the following processing methods 1) using a BB for pulverizing and 2) using a SS for chopping into tiny pieces. Each sample was duplicated into two wells during enzyme immunoassay (EIA) analysis to improve the accuracy of the obtained data. The results showed lower standard errors and constant output of FCC by using the BB method compared with the SS method. Overall comparison of FCC showed a significantly higher (p < 0.001) amount of the FCC in the BB compared with the SS. Overall, using the BB method is recommended over the SS method for feather processing due to the ability to homogenize a large number of samples simultaneously, ease of use and greater extraction of feather corticosterone.