Avian Research最新文献

Birds, a fascinating and diverse group occupying various habitats worldwide, exhibit a wide range of life-history traits, reproductive methods, and migratory behaviors, all of which influence their immune systems. The association between major histocompatibility complex (MHC) genes and certain ecological factors in response to pathogen selection has been extensively studied; however, the role of the co-working molecule T cell receptor (TCR) remains poorly understood. This study aimed to analyze the copy numbers of TCR-V genes, the selection pressure (ω value) on MHC genes using available genomic data, and their potential ecological correlates across 93 species from 13 orders. The study was conducted using the publicly available genome data of birds. Our findings suggested that phylogeny influences the variability in TCR-V gene copy numbers and MHC selection pressure. The phylogenetic generalized least squares regression model revealed that TCR-Vαδ copy number and MHC-I selection pressure were positively associated with body mass. Clutch size was correlated with MHC selection pressure, and Migration was correlated with TCR-Vβ copy number. Further analyses revealed that the TCR-Vβ copy number was positively correlated with MHC-IIB selection pressure, while the TCR-Vγ copy number was negatively correlated with MHC-I peptide-binding region selection pressure. Our findings suggest that TCR-V diversity is significant in adaptive evolution and is related to species’ life-history strategies and immunological defenses and provide valuable insights into the mechanisms underlying TCR-V gene duplication and MHC selection in avian species.

Nestling growth of birds can be affected by weather fluctuations. In general, it is expected that higher temperatures favor growth by improving food availability and nestling metabolism, while rain hinders it by reducing foraging efficiency. However, most of these patterns have been described in insectivorous cavity-nesting birds in temperate forests. We tested these predictions in two neotropical grassland ground-nesting birds with contrasting nestling diets and therefore potentially different responses to weather. We measured nestlings of the Hellmayr's Pipit (Anthus hellmayri, an insectivorous passerine) and the Grassland Yellow-Finch (Sicalis luteola, which feeds its nestlings exclusively with seeds) during three breeding seasons (2017–2020) in central-eastern Argentina. We took measurements of tarsus and body mass, modeled growth curves using nonlinear mixed-effects models, and evaluated the effects of minimum daily temperature and precipitation during the growth period and the 30 days prior to hatching. For pipits (60 nestlings from 21 nests), minimum temperatures during the growth period were positively associated with tarsus and body mass asymptotes. Also, there was a positive association between precipitation during the pre-hatching period and tarsus asymptote. Conversely, none of the weather variables analyzed had significant effects on nestling growth of finches (131 nestlings from 35 nests). Dietary contrast between species may explain the different results. Arthropod activity and abundance can be affected by weather variations within the span of a breeding season, whereas seeds may depend on conditions from previous years, making the effects harder to detect. Fledglings with reduced asymptotic size can have reduced chances of survival. Hence, pipit populations could be impacted if they experience cold and dry conditions during their breeding season, which is of major relevance in the current context of climate change.

In many songbird species, birdsong features phonological syntax, meaning that the units within their vocal sequences are ordered in a non-random way that adheres to a rule. While such syntactical patterns have been richly described in many species, comparatively little is known about how those patterns contribute to song achieving its important functions. For each of song's main functions, territorial defense and mate attraction, evidence of a role for syntax is limited. One species for which syntax has been thoroughly described is the Hermit Thrush (Catharus guttatus), which presents song types from their repertoires in a semi-predictable order and, in doing so, rapidly cycle up and down the frequency spectrum. The objective of the present study was to explore the importance of song syntax in the Hermit Thrush through a within-subject examination of how measures of syntax, such as the predictability of song type order within song sequences, shift over the breeding season. We hypothesized that, if such syntactical characteristics are important to breeding behaviour, they would be most prominent at the start of the breeding season when activity associated with territory establishment and mate attraction is most intense. Analysis revealed that, as predicted, the rigidness of song type ordering within sequences was highest at the start of the season and declined thereafter. That song type sequences were most predictable at the vitally important early part of the breeding season fit our hypothesis that this aspect of song syntax is important to song's functions related to territory establishment and/or mate attraction. Future work will clarify whether that role relates to one of song's two main functions or serves song transmission in some broader way.

Genetic load and inbreeding are recognized as important factors to be considered in conservation programs. Elevated levels of both can increase the risk of population extinction by negatively impacting fitness-related characters in many species of plants and animals, including humans (inbreeding depression). Genomic techniques are increasingly used in measuring and understanding genetic load and inbreeding and their importance in evolution and conservation. We used whole genome resequencing data from two sibling grouse species in subarctic Eurasia to quantify both. We found a large range of inbreeding measured as F_ROH (fraction of runs of homozygosity) in individuals from different populations of Chinese Grouse (Tetrastes sewerzowi) and Hazel Grouse (T. bonasia). F_ROH estimated from genome-wide runs of homozygosity (ROH) ranged from 0.02 to 0.24 among Chinese Grouse populations and from 0.01 to 0.44 in Hazel Grouse. Individuals from a population of Chinese Grouse residing in the Qilian mountains and from the European populations of Hazel Grouse (including samples from Sweden, Germany and Northeast Poland) were the most inbred (F_ROH ranged from 0.10 to 0.23 and 0.11 to 0.44, respectively). These levels are comparable to other highly inbred populations of birds. Hazel Grouse from northern China and Chinese Grouse residing in the Qinghai-Tibetan Plateau showed relatively lower inbreeding levels. Comparisons of the ratio between deleterious missense mutations and synonymous mutations revealed higher levels in Chinese Grouse as compared to Hazel Grouse. These results are possibly explained by higher fixation rates, mutational melt down, in the range-restricted Chinese Grouse compared to the wide-ranging Hazel Grouse. However, when we compared the relatively more severe class of loss-of-function mutations, Hazel Grouse had slightly higher levels than Chinese Grouse, a result which may indicate that purifying selection (purging) has been more efficient in Chinese Grouse on this class of mutations.

Variations in host traits that influence their exposure and susceptibility may impact probability of vector-transmitted diseases. Therefore, identifying the predictors of infection probability is necessary to understand the risk of disease outbreaks during expanding environmental perturbation. Here, we conducted a large survey based on microscopic examination and molecular analysis of haemosporidian parasite infection in raptors rescued at the Beijing Raptor Rescue Centre. Combining these data with biological and ecological variables of the raptors, we determined predictors that affect the probability of haemosporidian infection using generalized linear mixed models and multimodel inference. Our results showed that infection probability exhibited considerable variation across host species in raptors, and body mass, sex, and evolutionary history played relatively weaker roles in driving infection probability. Instead, activity pattern, age, geographic range size, migration distance, and nest type were important predictors of the probability of haemosporidian infection, and the role of each predictor differed in the three main haemosporidian genera (Plasmodium, Haemoproteus, and Leucocytozoon). This macro-ecological analysis will add to our understanding of host traits that influence the probability of avian haemosporidian infection and will help inform risk of emerging diseases.

Extra-pair paternity (EPP) is commonly found in socially monogamous birds, especially in small passerine birds, and there are interspecific and intraspecific variations in the extent of EPP. The Chestnut-vented Nuthatch (Sitta nagaensis) is a socially monogamous passerine bird, and verifying whether this species has EPP relies on parentage testing—S. nagaensis is not known to have EPP. In this study, we developed SNP markers of this species that are informative for parentage analysis from double digest restriction site-associated DNA sequencing (ddRAD-seq) data. A panel consisting of 50 SNP markers, with a mean heterozygosity of 0.343, was used to resolve 95% of nestlings to fathers. The combined exclusion probabilities for the first parent and second parent were 0.991 and 0.9999, respectively. This panel of SNP markers is a powerful tool for parentage assignments in S. nagaensis. In addition, we found that three offspring (7.9%) from three nests (23.1%) were the result of extra-pair fertilization out of 38 offspring in 13 nests. Our study provided information on parentage analysis that has not been reported before in S. nagaensis. It also supplemented the understudied EPP behavior of birds in Asia, contributing to a general understanding of the EPP behaviors of birds.

The interactions between avian brood parasites and their hosts provide an informative and easy-to-handle system for studying coevolution. Avian brood parasitism reduces the reproductive success of hosts, and thus, hosts have evolved anti-parasitic strategies, such as rejecting parasitic eggs and adopting aggressive nest defense strategies, to avoid the cost brought on by brood parasitism. To test whether host anti-parasitic strategies are adjusted with the risk of being parasitized when the breeding seasons of brood parasites and hosts are not synchronous, we conducted a field experiment assessing nest defense and egg recognition behaviors of the Isabelline Shrike (Lanius isabellinus), a host of the Common Cuckoo (Cuculus canorus). In the local area, the host Isabelline Shrike begins to breed in April, whereas the summer migratory Common Cuckoo migrates to the local area in May and begins to lay parasitic eggs. Results showed that nest defense behaviors of the Isabelline Shrike increases significantly after cuckoo arrival, showing higher aggressiveness to cuckoo dummies, with no significant difference in attack rates among cuckoo, sparrowhawk and dove dummies, but their egg rejection did not change significantly. These results imply that Isabelline Shrikes may adjust their nest defense behavior, but not egg rejection behavior, with seasonality.