CRC REEF RESEARCH CENTRE TECHNICAL REPORT No. 11

Populations, Movements And Site Fidelity Of Brown And Masked Boobies On The Swain Reefs, Great Barrier Reef, As Shown By Banding Recoveries.

P O'Neil, Queensland Department of Primary Industries & Fisheries
H Heatwole, Department of Zoology, North Carolina State Univeristy
M Preker, 321 Pullenvale Road, Pullenvale
M Jones, Department of Zoology, Univeristy of Tasmania

EXECUTIVE SUMMARY

Significant declines in the population size of the brown booby (Sula leucogaster) have recently been reported from the Swain Reefs (Heatwole et al. in review), as indicated through direct censuses of the populations over a period of more than ten years. During the same period of time, the population of the sympatric masked booby (Sula dactylatra) did not vary greatly. This paper reports on an extensive mark/recapture program of the same populations. The two species were banded and recaptured in the area for more than ten years.

Strong breeding colony fidelity has been demonstrated for both species in other parts of the world, leading to the suggestion that little gene flow occurs between geographically separate populations. These suggestions are supported by the present analysis of banding recoveries from the Swain Reefs, and other locations on the Great Barrier Reef and in the Coral Sea. In both these species, strong breeding colony fidelity appears to occur within the regional populations scattered over this broad area, but breeding site fidelity is weaker within the breeding populations of the closely spaced meta-population in the Swain Reefs. This suggests that some flexibility in management of human visitation is possible where closely spaced meta-populations of these species occur, but that displacement of a regional population may result in permanent loss, with little chance of re-colonisation from other regional populations.

Most of the extra-limital recaptures of both species were young birds. Masked boobies banded in the Swain Reefs were mostly recaptured along the Queensland coast, whereas brown boobies were mostly recaptured along the coasts of Papua New Guinea and in the Solomon Islands. This may indicate that only the young birds of these species disperse large distances, and that there are substantial differences in the between-species dispersal patterns. These differences may be relevant in explaining why a significant population decline occurred in the brown booby and not in the sympatric masked booby, but this requires further work.

THIS PUBLICATION IS CITED AS:
O'Neill, P., Heatwole, H., Preker, M., & Jones, M. (1996)
Populations, movements and site fidelity of brown and masked boobies on the Swain Rreefs, Great Barrier Reef, as shown by banding recoveries.
CRC Reef Research Centre Ltd
Technical Report No. 11
Townsville; CRC Reef Research Centre Ltd, 36 pp.

ISBN 1 876054 10 7.

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