O'Neill et al., 1996:

"During the period 1985 to 1994, 2044 brown boobies and 1817 masked boobies were banded on the Swain Reefs cays.  From these total numbers of banded birds, 339 brown booby and 728 masked booby recaptures (including multiple recaptures) were made during the same period. 

Extralimital recaptures indicate that most brown and masked boobies that disperse great distances, do so before sexual maturation.  These data also show that young brown boobies from the Swain Reefs tended to disperse north and east as far as the Solomon Islands and Papua New Guinea.  Young masked boobies were found to disperse mostly along the Queensland coast and the Great Barrier Reef.  The lower recapture rate of young brown boobies, and the decline in the brown booby population, may be associated with this geographical difference in dispersal areas.

Heatwole et al. (1996) suggested that decline in the brown booby population in the Swain Reefs was linked to reductions in food availability, possibly resulting from a succession of severe El Niño events.  However, it was difficult to explain why there was not a similar decline in the sympatric masked booby.  It is possible that differences in food availability occurred between the dispersal areas, with more severe food reductions in the area apparently favoured by immature brown boobies (Coral Sea).  Alternatively, there may have been an elevated mortality of immature brown boobies caused by changing human factors in the northern Coral Sea, such as fishing methods or intensity.  This type of information is not available. 

The extralimital recoveries show that some brown and masked boobies moved great distances from their breeding colonies in the Swain Reefs.  Even though most far distant recaptures were of young birds (age less than four years), this is not conclusive evidence of a more sedentary adult lifestyle.  Young birds may have been captured more often because, due to lack of experience, they were more likely to suffer from starvation than adults and be found in a weakened state.

While large geographical movements of brown and masked boobies are probably a population dispersal mechanism, the data presented in this report suggests that dispersal of breeding birds to other breeding colonies in the region does not regularly occur.

Gene flow within the meta-populations of both booby species in the Swain Reefs is probably substantial, but data from the present study suggests gene flow may be limited between the various populations scattered around the Coral Sea region.  Re-colonisation of sites that lose breeding populations would probably, therefore, be an uncertain and lengthy process.  It has previously been suggested that this might occur in seabirds that exhibit a high level of site tenacity (Drury 1979).  Resilience and adaptation have allowed brown and masked boobies to survive in a tropical environment, although their breeding success and survival in many areas is thought to be tenuous (Harrison 1990). Even subtle changes in breeding or feeding habitats, therefore, can possibly have catastrophic effects on survival.  This has important implications for management.  Populations of these two species which are geographically isolated from other breeding colonies must be managed to avoid all human disturbance, as the chance of re-colonisation appears to be low.  Public access should only be considered to minor colonies within closely spaced meta-populations, where re-colonisation from adjacent islands is a possibility. " 

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Citation and/or URL

O'Neill, P., Heatwole, H., Preker, M. and Jones, M. (1996). Populations, movements and site fidelity of brown and masked boobies on the Swains Reefs, Great Barrier Reef, as shown by banding recoveries. CRC Reef  Research Centre Technical Report No. 11 Townsville; CRC Reef Research Centre, 36pp. 

Spatial Coverage

Mostly the Great Barrier Reef Marine Park and the Coral Sea.

Temporal Coverage

1985 - 1994

Update Frequency

Not applicable 

Other Information

Drury, W.H. (1979).  Population Dynamics in Northern Marine Birds. In Bartonek, J.C. & D.N. Nettleship. Conservation of Marine Birds of Northern North America. Wildlife Research Report 11, U.S. Dept. of the Interior, Fish & Wildlife Service. Washington, D.C.

Harrison, C.S. (1990). Seabirds of Hawaii; Natural History and Conservation.  Cornell Univ. Press, Ithaca.

Heatwole, H., O'Neill, J.P., Jones, M. & Preker. M.  (1996). Long-term Population Trends for Seabirds in the Swain Reefs, Queensland.  Report submitted to the Cooperative Research Centre (Reef Research), Townsville, June 1996.  

See also seabird population connectivities