Habitat characteristics associated with occupancy of declining waders in Polish wet grasslands

Populations of meadow waders have shown steep declines in Europe during recent decades. However, empirical evidence concerning habitat preferences of different species in east Europe is largely lacking. In this study we investigate occurrence of the Eurasian curlew (Numenius arquata), black-tailed godwit (Limosa limosa), common redshank (Tringa totanus) and northern lapwing (Vanellus vanellus) in 413 grassland plots (c. 50,000 ha in total) located in Polish lowland surveyed three times during spring of 2015 and 2016. Using hierarchical occupancy models corrected for imperfect detection we link local water conditions, forest cover and scattered trees and presence of cows and buildings with occurrence of waders. Presence of godwit positively correlated with flooding and wetness while negatively with drainage ditches and single trees. Redshank was positively associated with flooding and negatively with ditches and proximity to buildings. Lapwing was less often observed in proximity to buildings and at sites with numerous trees whereas curlews, showed no clear associations with any of the environmental variables investigated. Detectability of studied species (except godwit) was higher when corvids were present suggesting that species interactions may affect detection. Field survey conditions (e.g. time of day, number of visit) also contributed to detectability of all studied species. Our study suggest that water availability, including natural flooding, increases habitat quality for breeding waders, while single trees and farm buildings may reduce grassland availability for these species. Thus waders-oriented agri-environment subsidies, besides adjusting grassland management to breeding phenology, should also focus on wetness and openness of grasslands.