Multi-scale habitat selection and nest survival of whinchats and stonechats: Implications for grassland conservation management

Effective management for endangered grassland birds requires a sound
understanding of habitat requirements and factors shaping reproductive
success. We studied multi-level habitat selection of endangered whinchats
(Saxicola rubetra) and locally increasing stonechats (Saxicola rubicola)
in a nature reserve using Sentinel-2 images, LiDAR data, and habitat
variables measured onsite. We monitored nest fates, and estimated how the
causes of nest mortality varied with nest initiation date. Further, we
analyzed how nest-site selection, precipitation, nest initiation date, and
nest age influenced daily nest survival. At landscape- and site-level,
both species primarily selected for territories in lightly farmed meadows.
However, stonechats appeared to be less specialized and used most
available habitat types. Within home-ranges, both species selected for
nest-sites in fallow patches, but in contrast to stonechats, whinchats
also selected for large viewsheds. In both species, the main causes of
nest failure were predation by red foxes (Vulpes vulpes), weather-related,
and nest desertion. In whinchats, the probability of nest desertion
increased and predation risk decreased with nest initiation date, possibly
due to better nest concealment in the later season. Daily nest survival
decreased with nest age and precipitation in both species, and increased
with nest initiation date in whinchats. None of the habitat variables
examined were positively linked to daily nest survival, and viewshed was
negatively related to whinchat daily nest survival. Our study suggests
that extending core habitat may help to promote settlement and potentially
reproductive success of whinchats. However, as habitat selection was not
positively associated with daily nest survival, land management measures
alone might not be sufficient to halt rapid population declines. To
effectively conserve whinchats and other grassland bird populations, the
causes of nest failures must be identified and addressed. Within the
examined reserve and similar habitats, targeted flood and predator control
may yield the biggest short-term conservation gains.