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.

Methods
This dataset contains the data for our analysis of multi-scale habitat selection and nest survival in whinchats and stonechats. In this paper, we analyzed territory selection of whinchats and stonechats at landscape- and site-level using compositional analysis, and nest-site selection at home-range-level using conditional logistic regression. We monitored the nest fates and analyzed how the causes of nest mortality varied with nest initiation date using a multinomial model. Further, we used known fate models to estimate how environmental and temporal factors influenced daily nest survival.