Selecting high-quality habitat and the optimal time to reproduce can increase individual fitness and is a strong evolutionary factor shaping animal populations. However, few studies have investigated ...the interplay between land cover heterogeneity, limitation in food resources, individual quality and spatial variation in fitness parameters. Here, we explore how individuals of different quality respond to possible mismatches between a cue for prey availability (land cover heterogeneity) and the actual fluctuating prey abundance.
We analyse timing of breeding and reproductive success in a migratory population of Eurasian kestrels (
) breeding in nest-boxes, over a full three-year abundance cycle of main prey (voles), and consider several components of individual quality, including body condition, blood parasite infection, and genetic diversity (
= 448 adults) that act on different time scales. Older individuals, and kestrel parents in higher body condition started egg-laying earlier than younger birds and those in lower body condition. Additionally, egg-laying was initiated earlier during the increase and decrease phases (2011 and 2012) than during the low phase of the vole cycle (2013). Nestling survival (ratio of eggs that fledged successfully) was higher in early nests and in heterogeneous landscapes (i.e., mosaic of different habitat types), which was evident during the increase and decrease phases of the vole cycle, but not during the low vole year.
We found a strong positive effect of landscape heterogeneity on nestling survival, but only when voles were relatively abundant, whereas a difference in the timing of breeding related to territory landscape heterogeneity was not evident. Therefore, landscape heterogeneity appeared as the main driver of high reproductive performance under favourable food conditions. Our results show that landscape homogenization linked to agricultural intensification disrupts the expected positive effect of vole abundance on reproductive success of kestrels.
Avian haemosporidian parasites (order Haemosporida, phylum Apicomplexa) are blood and tissue parasites transmitted by blood-sucking dipteran insects. Three genera (Plasmodium, Haemoproteus and ...Leucocytozoon) have been most often found in birds, with over 270 species described and named in avian hosts based mainly on the morphological characters of blood stages. A broad diversity of Haemoproteus parasites remains to be identified and characterized morphologically and molecularly, especially those infecting birds of prey, an underrepresented bird group in haemosporidian parasite studies. The aim of this study was to investigate and identify Haemoproteus parasites from a large sample comprising accipitriform raptors of 16 species combining morphological and new molecular protocols targeting the cytb genes of this parasite group. This study provides morphological descriptions and molecular characterizations of two Haemoproteus species, H. multivacuolatus n. sp. and H. nisi Peirce and Marquiss, 1983. Haemoproteus parasites of this group were so far found in accipitriform raptors only and might be classified into a separate subgenus or even genus. Cytb sequences of these parasites diverge by more than 15% from those of all others known avian haemosporidian genera and form a unique phylogenetic clade. This study underlines the importance of developing new diagnostic tools to detect molecularly highly divergent parasites that might be undetectable by commonly used conventional tools.
The globally endangered saker falcon (
) is currently being re-introduced in Bulgaria, where the falcons are bred in captivity and released through the hacking method. We relied on the birds' ...pedigree when forming the breeding pairs from 2011. In 2021-2022, we had the opportunity to evaluate our captive population via DNA tests. We performed the first genetic assessment of the sakers in the WRBC through a genome evaluation of the most important founders (n = 12) and, in 2022, we executed a microsatellite analysis on 30 saker falcons from the programme. We compared the results with the known pedigree and history of the saker falcons. The genetic tests helped to assign relatedness to some birds with missing or incomplete pedigrees, indicating the test can complement that information and lead to better management of the captive group. One pair was separated as a precaution as it was indicated by one the tests that the two birds are more closely related than expected. The research could be beneficial to other raptor captive breeding programmes dealing with a similar group composition.
Leucocytozoonosis is a vector-borne infection of birds, caused by members of the haemosporidian genus Leucocytozoon. The clinical presentation may range from asymptomatic to severe disease. ...Consequences of Leucocytozoon infection on blood profiles remain to be described, especially for different host species in the wild. In the current study, the prevalence of Leucocytozoon infection was determined in wild nestlings of three European raptor species, the common buzzard (Buteo buteo, n = 464), red kite (Milvus milvus, n = 46) and northern goshawk (Accipiter gentilis, n = 18). Among 528 nestlings, 51.9% (n = 274) were infected with Leucocytozoon spp., whereby the highest prevalence was found in common buzzards (54.9%), followed by red kites (32.6%) and northern goshawks (22.2%). For a subset of 87 individuals (50 common buzzards, 29 red kites, 8 northern goshawks), a detailed analysis of differential leukocyte counts and several blood chemistry parameters in response to infection was conducted: AP (alkaline phosphatase), AST (aspartate aminotransferase), GLDH (glutamate dehydrogenase), LDH (lactate dehydrogenase), GGT (gamma glutamyl transferase), CK (creatine kinase), BuChE (butyrylcholinesterase), BA (bile acids), ALB (albumin) and TP (total protein). Even though in the physiological range, infected nestlings displayed significantly increased levels of heterophils, aspartate aminotransferase, lactate dehydrogenase, bile acids and butyrylcholinesterase, but decreased lymphocyte and monocyte values compared to uninfected ones. Furthermore, significant species differences with regard to blood parameters, but no sex differences were found. Overall, obtained results show a high prevalence, but a low pathogenicity of Leucocytozoon spp. in wild raptor chicks, presumably resulting from coevolutionary adaptation, but show signatures of infection in the haematological and blood chemistry profiles.
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•Leucocytozoon prevalence in nestlings of three wild raptor species was 52%.•Common buzzards (Buteo buteo) showed the highest prevalence (55%).•Examined blood parameter values varied with species, age and infection status.•Leucocytozoon infections were associated with increased AST and BuChE.•Leucocytozoon infections in Accipitridae nestlings seem to be of minor pathogenicity.
Blood parasites of migrating yellow wagtails of two subspecies—
Motacilla flava feldegg
and
Motacilla flava flava
—were studied on a sample of 473 birds caught in spring and autumn periods in ...Bulgaria. We controlled eight “migration waves” (flocks captured in different evenings) of yellow wagtails for four parameters—average body mass, average fat level, average wing length, and average prevalence of different hematozoan species. Gametocytes or meronts of a total of six species of hematozoa belonging to three genera were identified—
Haemoproteus motacillae
,
Haemoproteus anthi
,
Plasmodium relictum
,
Plasmodium subpraecox
,
Plasmodium cathemerium
, and
Tryponosoma avium
. Mixed infections were detected in 31 cases, of which 14 were of
H. anthi
/
H. motacillae
type. Parasite species composition was similar in the two studied subspecies of
M. flava
. We did not find any significant differences in the overall infection prevalence or number of infecting parasites between
M. f. flava
and
M. f. feldegg
. Parasite prevalence and the number of co-infecting parasites in spring were much higher than in fall. Season had a strong influence on the prevalence of
H. anthi
and
H. motacillae
, and for both, there was a marginally significant interaction between subspecies and season, but not a season-independent influence of subspecies. Males of
M. f. feldegg
had a significantly higher overall blood parasite prevalence and prevalence of
H. anthi
than females. Sex-related differences in the prevalence of other parasites were not significant. Migration waves of yellow wagtails differed in overall infection status and in
H. motacillae
prevalence, but not for
H. anthi
prevalence. We also found significant differences in fat score, weight, and wing length between the studied migration waves of the yellow wagtails. Fat scores of birds infected with different hematozoa were lower compared with those of the non-infected birds. This only marginally was true for body weight and was not the case for wing length. Overall, infected birds were in worse condition (estimated as the residual weight after regression with wing length) compared with the non-infected birds, but after controlling for seasonal effects, the differences in condition appeared to be due to migration season and did not significantly differ between infected and non-infected birds caught in the same season.
Parents may adapt their offspring sex ratio in response to their own phenotype and environmental conditions. The most significant causes for adaptive sex-ratio variation might express themselves as ...different distributions of fitness components between sexes along a given variable. Several causes for differential sex allocation in raptors with reversed sexual size dimorphism have been suggested. We search for correlates of fledgling sex in an extensive dataset on common buzzards Buteo buteo, a long-lived bird of prey. Larger female offspring could be more resource-demanding and starvation-prone and thus the costly sex. Prominent factors such as brood size and laying date did not predict nestling sex. Nonetheless, lifetime sex ratio (LSR, potentially indicative of individual sex allocation constraints) and overall nestling sex were explained by territory quality with more females being produced in better territories. Additionally, parental plumage morphs and the interaction of morph and prey abundance tended to explain LSR and nestling sex, indicating local adaptation of sex allocation However, in a limited census of nestling mortality, not females but males tended to die more frequently in prey-rich years. Also, although females could have potentially longer reproductive careers, a subset of our data encompassing full individual life histories showed that longevity and lifetime reproductive success were similarly distributed between the sexes. Thus, a basis for adaptive sex allocation in this population remains elusive. Overall, in common buzzards most major determinants of reproductive success appeared to have no effect on sex ratio but sex allocation may be adapted to local conditions in morph-specific patterns.
Exploring the dynamics of gut microbiome colonisation during early-life stages is important for understanding the potential impact of microbes on host development and fitness. Evidence from model ...organisms suggests a crucial early-life phase when shifts in gut microbiota can lead to immune dysregulation and reduced host condition. However, our understanding of gut microbiota colonisation in long-lived vertebrates, especially during early development, remains limited. We therefore used a wild population of common buzzard nestlings (Buteo buteo) to investigate connections between the early-life gut microbiota colonisation, environmental and host factors.
We targeted both bacterial and eukaryotic microbiota using the 16S and 28S rRNA genes. We sampled the individuals during early developmental stages in a longitudinal design. Our data revealed that age significantly affected microbial diversity and composition. Nest environment was a notable predictor of microbiota composition, with particularly eukaryotic communities differing between habitats occupied by the hosts. Nestling condition and infection with the blood parasite Leucocytozoon predicted microbial community composition.
Our findings emphasise the importance of studying microbiome dynamics to capture changes occurring during ontogeny. They highlight the role of microbial communities in reflecting host health and the importance of the nest environment for the developing nestling microbiome. Overall, this study contributes to understanding the complex interplay between microbial communities, host factors, and environmental variables, and sheds light on the ecological processes governing gut microbial colonisation during early-life stages.
Differences in drug tolerability among vertebrate groups and species can create substantial challenges for wildlife and ex situ conservation programmes. Knowledge of tolerance in the use of new drugs ...is, therefore, important to avoid severe toxicity in species, which are both commonly admitted in veterinary clinics and are of conservation concern. Antimalarial drugs have been developed for use in human medicine, but treatment with different agents has also long been used in avian medicine, as haemosporidian infections play a major role in many avian species. This study investigates the effects of the application of atovaquone–proguanil (Malarone®, GlaxoSmithKline) in common buzzards (Buteo buteo). The potential effects of treatment on body condition, growth rate, and chemical blood parameters of nestlings were assessed. All individuals survived the treatment, and no effects on body condition, growth rate, and chemical blood parameters were observed. Our results suggest the tolerability of Malarone® in common buzzards at a single dose of on average 11 mg/kg body weight. For its safe use, we recommend further studies to determine pharmacokinetics in different avian species as well as to assess the effects of repeated treatment.
Avian haemosporidians are a common and widespread group of vector-borne parasites capable of infecting most bird species around the world. They can negatively affect host condition and fitness. ...Vultures are assumed to have a very low prevalence of these blood parasites, likely due to their strong immunity; however, factors contributing to variation in host exposure and susceptibility to haemosporidians are complex, and supporting evidence is still very limited. We analyzed blood samples collected from nestlings of three vulture species in Spain over 18 years, and used updated nested-PCR protocols capable of detecting all haesmosporidian cytochrome b lineages typical for diurnal birds of prey (Accipitriformes). Similarly to previous studies, we found low haemosporidian prevalence in cliff-breeding species, with
as the only represented blood parasite genus: 3.1% in griffon vultures (
) (
= 128) and 5.3% in Egyptian vultures (
) (
= 114). In contrast, the tree-breeding cinereous vulture (
) had a substantially higher prevalence: 10.3% (
= 146). By far the most common lineage in Spanish scavenging raptors was the
lineage CIAE02. No effects of nestling age and sex, or temporal trends in prevalence were found, but an effect of nest habitat (tree-nest vs. cliff-nest) was found in the griffon vulture. These patterns may be explained by a preference of vectors to forage in and around trees rather than on cliffs and wide open spaces. We found an apparent detrimental effect of haemosporidians on body mass of nestling cinereous vultures. Further research is needed to evaluate the pathogenicity of each haemosporidian lineage and their interaction with the immune system of nestlings, especially if compromised due to pollution with pharmaceuticals and infection by bacterial and mycotic pathogens.
By 2040, roughly two-thirds of humanity are expected to live in urban areas. As cities expand, humans irreversibly transform natural ecosystems, creating both opportunities and challenges for ...wildlife. Here, we investigate how the Northern Goshawk (
) is adjusting to urban environments. We measured a variety of behavioural and ecological parameters in three urban and four rural study sites. City life appeared related to all parameters we measured. Urban female goshawks were overall 21.7 (CI
5.13-130) times more likely to defend their nestlings from humans than rural females. Urban goshawks were 3.64 (CI
2.05-6.66) times more likely to feed on pigeons and had diets exhibiting lower overall species richness and diversity. Urban females laid eggs 12.5 (CI
7.12-17.4) days earlier than rural individuals and were 2.22 (CI
0.984-4.73) times more likely to produce a brood of more than three nestlings. Nonetheless, urban goshawks suffered more from infections with the parasite
, which was the second most common cause of mortality (14.6%), after collisions with windows (33.1%). In conclusion, although city life is associated with significant risks, goshawks appear to thrive in some urban environments, most likely as a result of high local availability of profitable pigeon prey. We conclude that the Northern Goshawk can be classified as an urban exploiter in parts of its distribution.
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