Extra-pair paternity and sperm length variation in the socially monogamous Fieldfare Turdus pilaris

Kleven O, Fiske AN, Havik M, Kroglund RT, Ostnes JE, Schmoll T. Extra-pair paternity and sperm length variation in the socially monogamous Fieldfare Turdus pilaris. JOURNAL OF ORNITHOLOGY. 2019;160(4):1043-1051.Basic knowledge about the genetic mating system is lacking for the great majority of the approximately 10,000 extant bird species. Filling this knowledge gap is not only critical for a comprehensive understanding of the reproductive ecology of each particular species, but also for increasing the power of comparative approaches to uncover and explain interspecific patterns of variation in avian reproductive traits. Using six polymorphic microsatellite markers, we here present the first parentage study in the socially monogamous Fieldfare Turdus pilaris. In parallel, we also examine variation in sperm morphology and relationships between sperm traits and paternity loss of social males. Across two study years, extra-pair paternity was detected in 46.4% (95% CI: 28.9-64.9%) of 28 broods, and on average 27.6% (95% CI: 16.8-41.9%) of nestlings per brood were extra-pair offspring in a population in central Norway. These observed extra-pair paternity rates fall within the range of reported estimates of extra-pair paternity for four congeneric Turdus species (between 36 and 65% of broods and 27 and 46% of nestlings). Sperm total length was 87.0 +/- 2.9 (SD) mu m (range 79.7-96.8 mu m) and 59.3% (95% CI: 37.1-73.3%) of the total phenotypic variation in sperm total length was explained by differences between sperm samples collected from 17 different males. The among-sample coefficient of variation in mean sperm total length was 2.70% (95% CI: 1.99-3.17%). We found no evidence for effects of sperm total length or relative midpiece length on loss of paternity among broods of 13 males

Tracking data highlight the importance of human-induced mortality for large migratory birds at a flyway scale

Human-induced direct mortality affects huge numbers of birds each year, threatening hundreds of species worldwide. Tracking technologies can be an important tool to investigate temporal and spatial patterns of bird mortality as well as their drivers. We compiled 1704 mortality records from tracking studies across the African-Eurasian flyway for 45 species, including raptors, storks, and cranes, covering the period from 2003 to 2021. Our results show a higher frequency of human-induced causes of mortality than natural causes across taxonomic groups, geographical areas, and age classes. Moreover, we found that the frequency of human-induced mortality remained stable over the study period. From the human-induced mortality events with a known cause (n = 637), three main causes were identified: electrocution (40.5 %), illegal killing (21.7 %), and poisoning (16.3 %). Additionally, combined energy infrastructure-related mortality (i.e., electrocution, power line collision, and wind-farm collision) represented 49 % of all human-induced mortality events. Using a random forest model, the main predictors of human-induced mortality were found to be taxonomic group, geographic location (latitude and longitude), and human footprint index value at the location of mortality. Despite conservation efforts, human drivers of bird mortality in the African-Eurasian flyway do not appear to have declined over the last 15 years for the studied group of species. Results suggest that stronger conservation actions to address these threats across the flyway can reduce their impacts on species. In particular, projected future development of energy infrastructure is a representative example where application of planning, operation, and mitigation measures can enhance bird conservation.publishedVersio