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Aspects of the breeding biology of the Reef Egret Egretta sacra


Reef Egret Egretta sacra nest site characteristics, nest attendance, vocalisations and eggs and chicks are described. Male and female Egrets spend equal time at the nest site at all stages of nesting. Incubation typically involved long sittings (mean of about 21.6 hours, standard deviation (s) = 9.46). The timing of feeding and nest attendance is correlated with the tidal cycle, but differences between Reef Egrets and colonial nesters, such as the Cattle Egret Ardeola ibis, might also come from the greater security provided by solitary nesting. Prior to egg-laying, the Reef Egrets leave their nests unattended for long periods while they feed at low tide. Male Cattle Egrets guard their nests continuously at this stage. The Reef Egret guards advanced chicks whereas the Cattle Egret does not. This guarding is only at high tide when there are fewer feeding opportunities and they perch some distance from the nest, possibly to avoid advertising its location. Compared with other egret species the Reef Egret would appear to have a small clutch and a long nesting season. A second brood is also indicated for some pairs. These may be adaptations to a chronic shortage of food for egrets in the coral reef environment.

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