Eastern Curlews Numenius madagascariensis Feeding on Macrophthalmus and Other Ocypodid Crabs in the Nakdong Estuary, South Korea

Abstract

Foraging Eastern Curlews were studied in the Nakdong Estuary, South Korea, in September 1984. During low tide Eastern Curlews spent on average 75-900io of their time foraging. They only ate crabs that had carapace widths 0.6 to 4 cm. Most crabs were captured with bill-deep probes in the crab-burrows. The majority of prey were the ocypodid crab species Macrophthalmus japonicus. Crabs with carapace widths longer than 2 cm were softly shaken to dismember their legs before consumption. The Eastern Curlew's average intake rate was estimated at 1.95 mg ash-free dry weight (AFDW) per sec foraging. Profitability (mg AFDW/ sec-handling) increased more than threefold over the range 0.6-3 cm carapace width. Comparisons with the foraging behaviour of two other curlew species, the Whimbrel Nurnenrus phaeopus and the Eurasian Curlew N. arquata, feeding on ocypodid fiddler crabs, are made. It is suggested that the easily available and abundant small crabs are not consumed because their profitability is too low.