Provision of Supplementary Nest Material to Colonial Egrets

Abstract

Colonies of tree-nesting birds are unable to occupy the same site for long periods if the nesting substrate dies and does not provide nest placement opportunities. One way vegetation is damaged is defoliation by birds collecting nest material. If birds accept supplementary nesting material from outside the colony site they would not need to take as many sticks from live trees in it. This trial was designed to determine if supplementary sticks would be taken by Great Ardea alba, Intermediate A. intermedia, Little Egretta garzetta and Cattle A. ibis Egrets and, if so, whether there was a preference for particular species; from what locations within the colony sticks were taken, and at what stage of the nesting season? Sticks of several species were taken by all four egrets immediately nesting began, and during the height of nest construction the egrets collected sticks from dry land plots placed up to 5 m from the colony edge. Such nest material supplementation may reduce tree defoliation and lead to greater nest attentiveness, with enhanced breeding success in larger nests through fewer eggs and chicks falling out and greater thermal insulation.