The relationship between riverbed flooding and non-breeding Wrybills on northern feeding grounds in summer

Abstract

I investigated the relationship between floods on the riverbed breeding grounds of Wrybills (Anarhynchus frontalis) and the number of Wrybills censused on northern harbours the following summer. For the purposes of the study I assumed that most birds oversummering on northern harbours are first-year non-breeders and that flood flows of the Rakaia River are representative of most other Wrybill breeding rivers. A highly significant negative correlation (r²=0.69; p<0.01) existed for the 1968-1982 period. The study's findings provide some support for the observation that by the early 1960s the Wrybill population, after many years of growth, had begun to stabilise. Serious flooding in the 1982 and 1983 breeding seasons may have again destabilised the population structure.