Emu Emu Society
Journal of BirdLife Australia

Breeding biology of Masked Boobies (Sula dactylatra tasmani) on Lord Howe Island, Australia

David Priddel A E , Ian Hutton B , Samantha Olson C D and Robert Wheeler A
+ Author Affliations
- Author Affliations

A Department of Environment and Conservation, PO Box 1967, Hurstville, NSW 2220, Australia.

B Lord Howe Island Nature Tours, PO Box 157, Lord Howe Island, NSW 2898, Australia.

C Lord Howe Island Board, PO Box 5, Lord Howe Island, NSW 2898, Australia.

D Present address: Department of Environment and Conservation, PO Box 3031, Asquith, NSW 2077, Australia.

E Corresponding author. Email: david.priddel@environment.nsw.gov.au

Emu 105(2) 105-113 https://doi.org/10.1071/MU04028
Submitted: 26 May 2004  Accepted: 22 April 2005   Published: 30 June 2005


The breeding biology and reproductive output of a colony of Masked Boobies on Mutton Bird Point, Lord Howe Island, Australia, were studied during the 2001–02 breeding season. The colony produced a total of 200 clutches. Eggs were laid between 31 May and 15 September 2001, with 80% of clutches begun before 21 July. More than 90% of clutches consisted of two eggs, laid, on average, 5.3 days apart. Mean incubation period was 45 days. Where both eggs hatched, the later-hatched chick had to compete with an aggressive elder sibling of greater mass; consequently, it seldom survived longer than 1 week. Hatching success was 38% for single-egg clutches, 81% for two-egg clutches and 78% overall. For two-egg clutches, 13% of successful chicks hatched from the second egg. In keeping with the comparative mass of adults, eggs and chicks from Lord Howe Island were larger than those from any other Masked Booby population where measurements have been made. Chick mass increased steadily to reach a maximum of 2235 ± 292 g (equivalent to mean adult mass) at 11 weeks of age. Overall, fledging success was 65%, but was greatest for eggs laid early in the breeding season. There was no difference in fledging success between chicks that were handled weekly and those that were handled only once. Overall breeding success was 51%. Rats were not a significant predator of eggs or chicks, and no other predators or land-based threats were identified. Clutch-size indicated that, at the time of laying, the Masked Booby population on Lord Howe Island was well nourished, but decreasing rates of hatching and fledging success, and less than optimal growth rates of chicks, suggested food availability declined during the nesting period. Regurgitations indicated that flying fish were the main prey.


Adam Bester, Lisa O’Neill and Nicolas Carlile assisted with the collection of data in the field. This project was conducted under NPWS Scientific Licences A2635 and A697, Banding licences 8010, 1208, 1373, and 1867, and Animal Care and Ethics Approval 010816/01. Leg-bands were supplied by the Australian Bird and Bat Banding Scheme.


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