Cattle Egret migration, satellite telemetry and weather in south-eastern Australia

Two adult Cattle Egrets, captured near Raymond Terrace in the Williams River Valley, New South Wales, in April 1994 were each fitted with a PTT100, battery-powered transmitter and with patagial tags. After release, the birds were tracked by Argos system satellite on an eight hours on and 40 hours off duty cycle and ground searches were carried out to locate them by their tags. Weather maps from the Bureau of Meteorology associated with each satellite interrogation were evaluated. After remaining in the vicinity of the capture site for several weeks, the birds were further tracked until signals were lost, one on a migration route in the Lower Hunter floodplain and the other on a southerly migration to Bega in south-eastern New South Wales, following patterns described in Maddock and Geering (1994). The movements occurred in light winds under the influence of a high pressure system. The results of this pilot study suggest the potential for using small satellite transmitters for migration studies of egrets, to assist in validation of other field techniques and to provide data not obtainable by other techniques.

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