Eastern Curlew numbers at high-tide roosts versus low-tide feeding grounds: a comparison at three spatial scales

Abstract

We compared summer numbers of the Eastern Curlew (Numenius madagascariensis) in Moreton Bay counted on low-tide feeding grounds with those counted on high-tide roosts, at several spatial scales. In total, the average summer count at 30 focal roost sites was 1851 and the corresponding average summer count at adjacent feeding grounds was 1728, a close match given the potential sources of error in both data sets. Counts also corresponded well when feeding grounds were broken up into smaller-scale groups and associated with adjacent roost sites. Larger-area (around 5 km) groupings of continuous feeding habitat gave high levels of association (76-83% of the variation in roost-site numbers explained by variation in feeding-site numbers), which weakened when the sites were grouped at a finer scale (around 500 m), although it remained statistically significant (42% of variation explained). Within Moreton Bay, the distance over which the Eastern Curlew typically operate may be in the order of 5-10 km, with high mobility between alternate roosts and/or feeding grounds occurring at or below this distance.