Black-tailed Godwit abundancies across key European breeding habitats

The endangered continental Black-tailed Godwit (Limosa limosa limosa) is a
migratory ground-nesting wader breeding in a wide variety of open, wet
habitats across Europe. Conservation research has concentrated on the
causes of population decline, but we know surprisingly little about
whether any resources limit local breeding populations and, if so, whether
these are resources for the adults or the chicks. We collected data from
63 key breeding sites in five countries across Europe to test whether,
after correcting for differences in surveyed areas, the size of Godwit
breeding populations was related to environmental variables (vegetation
biomass, soil moisture) or food resources for adult birds (soil
invertebrates) or chicks (vegetation dwelling arthropods) measured during
different times of the reproductive cycle. We found the number of Godwit
territories to be positively related to arthropod abundance during the
chick-hatching period. We found additional, weaker support for a positive
relation between Godwit territory numbers and the abundance of
soil-dwelling invertebrates (mostly earthworms) at clutch laying, but not
at chick-hatching. These relationships were observed across countries,
while we found little support for relationships within countries, possibly
due to the smaller range in conditions that exist within countries. Both
vegetation growth and soil moisture weren’t related to Godwit territory
numbers. Our results suggest that food abundance for chicks, and to a
lesser extent adult birds, are key factors determining the size of local
Godwit breeding populations. Conservation management aiming to enhance
local Godwit populations should therefore consider the impacts of
management strategies on the arthropod prey of chicks.