Reconstructing diet composition on the basis of faeces in a mollusc-eating wader, the Knot Calidris canutus

Methods are described to assess the molluscan diet of Knots feeding on intertidal flats in western Europe from their faecal output. The size distributions of two common bivalve prey, Macoma balthica and Cerastoderma edule, can be estimated from the heights of shell hinges retrieved from droppings. The average ingested size of the tiny mudsnail Hydrobia ulvae can be reconstructed from partially broken shells. Diet composition in terms of biomass can be estimated by a two-step procedure. First, the diet composition in terms of ash or shell mass is estimated on the basis of the sieved mass of droppings. The application of the site-, season- and size-specific ratios of biomass/shell mass or biomass/ash mass then provides a breakdown of diet with respect to biomass. An exploratory field study in the Wadden Sea showed that measurable fragments in (rarely encountered) regurgitates overestimate prey size. According to the faecal analysis, there was a seasonal change in diet from bivalves to mudsnails with the app...

[1]  J. Goss‐Custard.  The Responses of Redshank (Tringa totanus (L.)) to Spatial Variations in the Density of their Prey , 1970 .

[2]  R. Green.  The feeding ecology and survival of partridge chicks (Alectoris rufa and Perdix perdix) on arable farm-land in East Anglia , 1984 .

[3]  T. Piersma.  Production by intertidal benthic animals and limits to their predation by shorebirds : a heuristic model , 1987 .

[4]  E. Young.  Diet of the south polar skua Catharacta maccormicki determined from regurgitated pellets: limitations of a technique , 1990, Polar Record.

[5]  J. Goss‐Custard.  Responses of Redshank, Tringa totanus, to the Absolute and Relative Densities of two Prey Species , 1977 .

[6]  L. Zwarts,et al.  Seasonal trend in burrow depth and tidal variation in feeding activity of Nereis diversicolor , 1989 .

[7]  R. Major.  Stomach Flushing of an Insectivorous Bird - an Assessment of Differential Digestibility of Prey and the Risk to Birds , 1990 .

[8]  A. Prater.  The Ecology of Morecambe Bay. III. The Food and Feeding Habits of Knot (Calidris canutus L.) in Morecambe Bay , 1972 .

[9]  William J. Sutherland,et al.  Do oystercatchers select the most profitable cockles? , 1982, Animal Behaviour.

[10]  D. B. Edwards,et al.  Seasonal changes in flesh weight and biochemical composition of mussels (Mytilus edulis L.) in the Conwy Estuary, North Wales , 1975 .

[11]  D. Duffy,et al.  Diet Studies of Seabirds: A Review of Methods , 1986 .

[12]  J. Beukema,et al.  Seasonal changes in dry weight and chemical composition of the soft parts of the tellinid bivalve Macoma balthica in the Dutch Wadden Sea , 1977 .

[13]  L. Zwarts,et al.  Siphon size and burying depth in deposit- and suspension-feeding benthic bivalves , 1989 .

[14]  N. Davies.  Prey Selection and Social Behaviour in Wagtails (Aves: Motacillidae) , 1977 .

[15]  L. Zwarts.  Seasonal variation in body weight of the bivalves Macoma balthica, Scrobicularia plana, Mya arenaria and Cerastoderman edule in the Dutch Wadden sea , 1991 .

[16]  M. Leopold,et al.  Time-stressed oystercatchers, Haematopus ostralegus, can increase their intake rate , 1989, Animal Behaviour.

[17]  L. Zwarts,et al.  Why knot Calidris canutus take medium-sized Macoma balthica when six prey species are available , 1992 .

[18]  L. Zwarts,et al.  Annual and seasonal-variation in the food-supply harvestable by knot Calidris-canutus staging in the Wadden Sea in late summer , 1992 .

[19]  R. Green,et al.  Determination of the diet of the stone curlew (Bwhinus oedicnemus) by faecal analysis , 1989 .

[20]  G. Cadée,et al.  Tissue composition and reproduction of mytilus edulis in relation to food availability , 1980 .

[21]  R. Williams,et al.  The Ecology of the Wash. II. Seasonal Variation in the Feeding Conditions of Wading Birds (Charadrii) , 1977 .

[22]  M. R. Chambers,et al.  The production of Macoma balthica (L.) in the Ythan Estuary , 1975 .

[23]  J. Beukema.  Calcimass and carbonate production by molluscs on the tidal flats in the Dutch Wadden Sea: II the edible cockle, cerastoderma edule , 1982 .

[24]  P. Meire.  Foraging Behavior of Some Wintering Waders: Prey-Selection and Habitat Distribution , 1987 .

[25]  J. Goss‐Custard,et al.  Seasonal changes in the size selection of mussels, Mytilus edulis, by oystercatchers, Haematopus ostralegus: an optimality approach , 1990, Animal Behaviour.

[26]  D. Worrall.  Diet of the Dunlin Calidris alpina in the Severn Estuary , 1984 .

[27]  J. Beukema.  Calcimass and carbonate production by molluscs on the tidal flats in the Dutch Wadden Sea: I. The tellinid bivalve Macoma balthica , 1980 .

[28]  S. Durell,et al.  Diets of Dunlin Calidris alpina and Grey Plover Pluvialis squatarola on the Wash as determined by dropping analysis , 1990 .