Saving our seabirds: variable breeding success of Red-tailed Tropicbirds in the Great Barrier Reef reveals the need for robust monitoring

Abstract

Quantifying nest success for seabirds breeding in remote offshore islands can be logistically challenging, especially for species with protracted breeding phenologies. Thus, any monitoring program must be robust to these challenges, but few studies have reported evaluations of survey design, monitoring frequency, and methods for estimating nesting success for such species. We explored whether the current monitoring program for Red-tailed Tropicbirds (Phaethon rubricauda) on Raine Island, Great Barrier Reef, Australia, enabled accurate estimates of nesting success. We use three different approaches to produce the first estimates of nesting success from data collected by this monitoring program. Annual nesting success for Red-tailed Tropicbirds was low at Raine Island, estimated as between 24.3% and 30.6%, indicating that further study is warranted to identify possible causes. However, our study illustrates possible pitfalls of the monitoring program, and we propose three critical considerations (maximising per-nest observations, standardising timing of visits, and using automated technologies) that would improve the ability of monitoring programs to estimate nesting success for seabirds with protracted breeding phenologies. Use of such modifications in monitoring programs will improve our ability to diagnose the causes of population declines for seabirds in the Great Barrier Reef.