Nine years (1989/90-2002) of data on a asynchronous pelagic seabird, the White-tailed Tropicbird (Phaethon lepturus), breeding on Aride Island, Seychelles, were used to examine: (1) annual variation in productivity and, (2) the importance of large scale (El Niño Southern Oscillation) factors in explaining productivity levels. In 2001 and 2002, we examined the influence of local scale factors (parasitism by hard ticks Amblyomma loculosum and intra- and inter-specific competition for nest-sites) on productivity. Productivity between years only ranged from 0.21 to 0.37 chicks/breeding pair, but it was nevertheless significantly and inversely correlated with the El Niño index. No influence on productivity was caused by local factors. The frequency distribution of chick deaths varied significantly with chick age in 2001 but not in 2002. Most of the chick deaths were from starvation, in particular for chicks older than 20 days. As opposed to synchronous seabird species, there were no years with total breeding failure in the White-tailed Tropicbird. This may be partly explained by their dispersed feeding in the open ocean.
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1 December 2005
Productivity of White-Tailed Tropicbird on Aride Island, Seychelles
Jaime A. Ramos,
John Bowler,
Michael Betts,
Carlos Pacheco,
Jamie Agombar,
Ian Bullock,
David Monticelli
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Waterbirds
Vol. 28 • No. 4
December 2005
Vol. 28 • No. 4
December 2005
asynchronous breeding
breeding success
Phaethon lepturus
tropical seabirds
variation in fecundity rates
White-tailed Tropicbird