Census and Distribution of Black Noddy Anous minutus Nests on Heron Island, November 1985

Abstract

A census of Black Noddy nesting density on Heron Island in late November 1985 returned an estimate of 40 718 ± 3214 (X ± s.e.) active nests, an increase of 10.5% over the most recent previous survey conducted in 1983 and 39% higher than a survey In 1982. An assessment of habitat usage indicated that Black Noddies nest in all species of tree found on the island, even in Casuarina in which few or no nests have previously been reported. With the possible exception of Ficus and Celtis there was no clear indication that any species were preferred for nesting when tree and shrub size were considered. However, 75% of nests were found in Pisonia, predominantly in large ones. The numbers of birds nesting in the eastern and western halves of the island were almost identical despite the extensive development, tree loss and human presence In the west. In the developed half of the island there were greater numbers of nests per tree in the important nesting species, which almost completely compensated for the lower density of trees.