Seasonal variation in the diet of Redshank Tringa totanus in the Odiel Marshes, southwest Spain: a comparison of faecal and pellet analysis

Abstract

Aims To assess seasonal variation in Redshank diet at a major passage site, and to compare data derived from analysing pellets or faeces.

Methods At the Odiel Marshes in 2001, pellets from spring migration (39), autumn migration (121) and midwinter (15) were analysed, together with faecal samples from autumn (84).

Results The abundance of different invertebrate groups in pellets varied between seasons. In spring, Chironomus salinarius pupae and larvae dominated by volume, followed by Ephydridae larvae and the beetle Paracymus aenus. Polychaetes and molluscs dominated in autumn, and isopods in midwinter. In autumn, chironomid larvae, Mesembryanthemum nodiflorum seeds and Artemia cysts were relatively more abundant in faeces, whereas polychaetes, isopods, molluscs and cestode cysticercoids were more abundant in pellets. Harder and/or larger items were thus relatively more abundant in pellets than faeces. Pellet analysis gave more emphasis to mudflat prey, and faeces to saltpan prey.

Conclusion Pellet and faecal analysis give different results for wader diet, and it is useful to combine the two methods. However, they show significant correlations both in diet range and rank abundance of prey items. Redshank diet shows much seasonal and spatial variation in southern Europe.