Ardea
Official journal of the Netherlands Ornithologists' Union

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Hulscher J.B., Alting D., Bunskoeke E.J., Ens B.J. & Heg D. (1996) Subtle differences between male and female Oystercatcher Haematopus ostralegus in feeding on the bivalve Macoma balthica. ARDEA 84 (A): 117-130
In this paper an analysis is made of subtle behavioural differences between adult male and female Oystercatchers feeding on Macoma balthica under field conditions and in captivity. Macoma is a tellinid bivalve that in the Dutch Wadden Sea is mainly preyed upon during spring and summer when it is buried at a shallow depth. ## lift Macoma more, whereas ~~ handle them mostly in situ. Both sexes handle a Macoma in situ faster than one lifted. Time loss of ## in handling more lifted Macoma is compensated by the larger size of lifted Macoma, which yields more flesh. The time the birds need to find an edible Macoma is similar for both sexes, resulting in equal mean food intake rates for ## and ~~ in the field. Lifted Macoma are generally hammered and, since ## with their short strong bills are more likely to hammer bivalves than ~~, this difference in bill morphology might explain why ## more often lift Macoma than do ~~, especially as hammering produces a blunt bill tip which would reduce efficiency at opening Macoma in situ. However, none of the selected bill morphology variables showed a relationship within the sexes that explained the differences between the sexes.


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