Why do curlewsNumeniushave decurved bills?

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Abstract
The functions of the long, decurved bill of the Common Curlew are compared with those of the straight bill of the Bar-tailed Godwit. Comparison is also made with the dimensions of other species of curlews and godwits. We argue that decurvature is adapted to a technique of prey capture in which the bill tip follows a complex three-dimensional search path, and that the long bill of the Common Curlew is adapted to the intact removal of long prey (e.g. worms) from mudflats. The evidence indicates that strong selection for bill form operates on the wintering grounds.