Prey and Prey Size Selection by the Near-Threatened Black-tailed Godwit Foraging in Non-Tidal Areas during Migration

Near-threatened Black-tailed Godwits Limosa limosa and other shorebirds rely on non-tidal areas during their annual migration but understanding of stopover ecology in these areas is lacking. Here, field observations, analysis of droppings and prey abundance were combined to investigate diet and prey-size selection by Black-tailed Godwits during fall migration in salinas (also called salt works or salt ponds) of southern Europe. Although several potential macroinvertebrate prey species were available and abundant, godwits positively selected the chironomid Chironomus satinarius. The larvae and pupae of this prey represented >95% of the total number of items present in droppings during migration (July-September). Consumption of prey of a given size class was not dependent on its abundance. Thus, although larger size-classes of chironomid larvae were not necessarily the most abundant for some months (mean size of available larvae: 8.2 +/- 0.2 mm, 6.4 +/- 0.2 mm and 8.4 +/- 0.2 mm in July, August and September, respectively), they were the ones most frequently consumed by the godwit (mean size of larvae predated: 9.9 +/- 0.8 mm, 9.2 +/- 1.7 mm, and 9.4 +/- 1.3 mm in July, August and September, respectively). The role salinas play as stopover foraging areas for godwits appears dependant not only on the abundance of C. salinarius but also on the abundance of large size-classes of this soft-bodied prey. Conservation and management of salinas that allows the production of high densities of chironomids during the peak of Black-tailed Godwit migration would assist the conservation of this species. Received 22 December 2009, accepted 30 April 2010.