This paper describes aspects of the winter feeding ecology of Black-ta
iled Godwits Limosa limosa on an intertidal mudflat in the Tagus estua
ry, Portugal. Their diet consisted mainly of the bivalve mollusc Scrob
icularia plana, which represented 88% of the ingested biomass. The rem
aining 12% was the worm Nereis diversicolor and, occasionally, the sna
il Hydrobia ulvae. Ingested Scrobicularia varied between 10 and 20 mm
in length, and all size classes of Nereis present in the sediment, exc
ept those smaller than 20 mm, were preyed upon. A change in dietary co
mposition occurred over the winter, probably in response to changes in
the availability of Nereis and small Scrobicularia. Intake rates aver
aged 74.9 mg dry weight per minute, which corresponded to a net energy
intake of 1.21 kJ per min.