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Egret nests and cherry pickers: a cautionary tale


From 1997 to 1998 the reproductive biology of a colony of Great Egrets Ardea alba at the Perth Zoo, Western Australia was studied. A cherry picker was used to provide elevation so that an accurate and rapid count of the number of active nests, eggs and chicks, nesting material and the size of nests and position in the trees could be made. The presence of the cherry picker near the Great Egret colony caused seven chicks to fall to the ground,with two of the seven chicks that fell surviving. Although some mortality occurred, the information obtained using the cherry picker could not have been obtained from observations taken from the ground, due to the height of the nests in the trees. As the colony is the only remaining Great Egret colony in the Perth metropolitan region, an accurate count was necessary to establish a baseline against which long term fluctuations in numbers could be assessed. The cherry picker counts, although causing several deaths, have allowed the accuracy of previous and future ground counts to estimated. Long-term monitoring of this colony can therefore be continued from the ground.

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