Thursday, January 6, 2011

Feeding Challenges for the Oystercatcher

Oystercatcher, Haematopus ostralegus
The Oystercatcher (Haematopus ostralegus, the Eurasian or Pied Oystercatcher) is one of the largest, and most striking wading birds in Ireland. A resident here all year round, it tends to stick to undisturbed shores when breeding, but is readily visible outside of this time on beaches and estuaries where large flocks often roost (1). It is plover in shape, but has a distinctive black and white colouring with long pink legs and piercing red eyes. Its stout yellow bill is used to feed on molluscs (predominantly mussels, despite its name) and shows three distinct shapes: pointed, chisel shaped and blunt (2).
Feeding can be quite an ordeal for the Oystercatcher. To begin with, there is stout competition for food to deal with. While the different bill types helps to reduce interspecific competition (2), dominance hierarchies exist at feeding sites where intake by subdominant individuals decreases with increasing bird densities (3). Dominant individuals at these sites suffered no such decrease. Feeding can be further restricted by shortened foraging times due flooded feeding areas. The Oystercatcher has been shown to be more than capable of meeting this challenge. In simulated shorter foraging times, birds spent proportionally more time foraging, shortened their searching time per prey item taken and decreased the time spent handling prey (4). This resulted in no decrease in consumption.

  1. Sterry, 2004 Collins Complete Guide to Irish Wildilfe p. 50
  2. Swennen et al. 1983 Netherlands Journal of Sea Research 17 pp. 57-83
  3. Ens and Goss-Custard, 1984 Journal of Animal Ecology 53, pp. 217-231
  4. Swennen et al., 1989 Animal Behaviour 38 pp. 8-22

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