Data from: Complex migration and breeding strategies in an elusive bird species illuminated by genetic and isotopic markers

Unlike the annual bi-directional movements of over 200 bird species within
the Palaearctic–Afrotropical region, irregular movements such as irruptive
migration with a low degree of philopatry are reported for a variety of
species depending on highly seasonal and unpredictable resources. These
flexible movements allow for itinerant breeding – consecutive breeding
attempts in two or more geographically different regions during the same
annual reproductive cycle. In order to illuminate migratory and breeding
strategies of the erratic wetland species Baillon's crake Zapornia
pusilla across the W-Palaearctic–Afrotropical region, we used a set of six
DNA microsatellites as well as δ2Hf values of individuals sampled at one
African and four European breeding sites. We investigated the degree of
genetic population structure within and among different sites and assigned
individuals’ feathers of unknown origin to their probable moulting (hence
breeding) site using a likelihood approach. We found three genetic
clusters, differentiating into one ‘European’ and two ‘African’
populations. Connectivity between the sampling sites was probable as
genetic ‘African’ individuals were found in breeding conditions in Europe
and vice versa. Likewise, assigned moulting locations based on δ2H
isoscapes suggested trans-continental movements as well as moulting and
possibly breeding by the same individual both in African and European
breeding grounds. Both isotopic and genetic data reveal the Baillon's
crake pursue a complex migration and breeding strategy, allowing as well
for irruptive movements and itinerant breeding across the
W-Palaearctic–Afrotropical region. However, a better knowledge about the
species’ distribution as well as a more comprehensive data set, including
samples from the southern and eastern boundaries of the distribution area
would be necessary to improve the spatial resolution to the precision
required to unambiguously infer migration directions and extent of
exchange between African and European breeding grounds.