Establishment of a new, secure colony of Endangered Bermuda Petrel Pterodroma cahow by translocation of near-fledged nestlings

Abstract

SummaryUntil recently, Bermuda Petrel Pterodroma cahow (IUCN Category: ‘Endangered’) bred only in sub-optimal habitat on four small islets in north-east Bermuda. Although intensive management of the population since 1962 has led to a substantial increase in population size (now approaching 100 pairs), the nesting habitat on these four islets is being increasingly inundated, eroded and destroyed by high seas associated with hurricanes and storms. To ensure the long-term conservation of the species a decision was made to establish a new colony at a more secure site on nearby Nonsuch Island, where they once bred in large numbers. Between 2004 and 2008, 104 near-fledged nestlings were translocated to artificial burrows on Nonsuch Island, where they were hand-fed meals of fish and squid. All but three translocated birds fledged successfully, with the first returning to Nonsuch Island in February 2008. The first Bermuda Petrel egg on Nonsuch Island in more than 300 years was laid in January 2009, and the resultant fledgling departed in June of the same year. By the end of the 2009/10 breeding season, a total of 18 Bermuda Petrels have been recorded on Nonsuch Island, 17 were translocated as near-fledged nestlings, and one bird came from the existing colonies. A total of five eggs have been produced, resulting in two fledglings. The establishment of this new colony, at a site that is much more secure than the existing nesting sites, greatly enhances the conservation prospects of the species and demonstrates the importance of translocation as a tool for the conservation of threatened seabirds.

Are artificial burrows efficient conservation tools for seabirds? A case study of two sympatric shearwaters on neighbouring islands and guidelines for improvement

“…In our study, PVC was the lightest, cheapest and the least work demanding material for artificial burrow construction as the various parts were readily available and only necessitated some cutting and drilling. Artificial burrow materials can affect temperature inside burrows (Miskelly et al, 2009;Carlile et al, 2012). However, we did not find a significant effect of construction material on reproductive success of either Yelkouan or Scopoli's shearwaters while it affected occupancy rate by Yelkouan shearwaters.…”

“…They can be used to supplement available suitable breeding habitat (Priddel and Carlile, 1995;Lalas et al, 1999;De León and Mínguez, 2003;Bried et al, 2009;Madeiros et al, 2012;Sherley et al, 2012), increase breeding success and adult survival (Byrd et al, 1983;Priddel and Carlile, 1995;De León and Mínguez, 2003;Bolton et al, 2004;Libois et al, 2012;Sherley et al, 2012), decrease inter-specific competition for nesting habitat (Wingate, 1977;Ramos et al, 1997;Sullivan and Wilson, 2001;Bolton et al, 2004;Gummer et al, 2015), establish new breeding sites when coupled with chick translocation and/or vocal attraction (Podolsky and Kress, 1989;Bell et al, 2005;Miskelly and Taylor, 2004;Priddel et al, 2006;Miskelly et al, 2009;Carlile et al, 2012;Gummer et al, 2015), and make the study of breeding biology and habits easier and less disturbing (Wilson, 1986(Wilson, , 1993Bolton, 1995;Gaston, 1996;Gummer et al, 2015). Occupancy rates of artificial burrows generally increase over time and high rates (N20%) have been reported for many seabird species either from the first breeding season after artificial burrow installation (Wilson, 1986(Wilson, , 1993Bolton, 1995;Ramos et al, 1997;Lalas et al, 1999;Sullivan et al, 2000;Bried et al, 2009), or from 2 to 4 breeding seasons after installation, as occupancy rates can take years to build up …”

Managing Marine Biodiversity: The Rising Diversity and Prevalence of Marine Conservation Translocations

“…Some of the marine birds and mammals of highest conservation concern, such as the vaquita (Phocoena sinus) or the Chinese crested tern (Thalasseus bernsteini), may be more challenging candidates for translocations, for example because no wild population is sufficiently numerous to act as a source, captive breeding is difficult, transport logistics or public opposition impede translocations, or the species is philopatric and highly motile, thus unlikely to remain near the release site. However, such challenges have not prevented conservation translocations of Bermuda petrels (Pterodroma cahow; Carlile et al 2012), gray seals (Halichoerus grypus; Duguy & Prieur 1980), or many terrestrial species [e.g., the whooping crane (Grus americana) or California condor (Gymnogyps californianus)], for that matter. Factors influencing the diversity of marine conservation translocations may be biological, social, and/or logistical, but it is clear that invertebrate and plant species are the most common subjects of conservation translocations in oceans, and ecosystem recovery is the primary objective.…”

Breeding biology and population increase of the Endangered Bermuda Petrel Pterodroma cahow

“…The largest increase is projected to occur in the Western Atlantic, north of 20°N, in the region where Bermuda is located. Accelerating storm damage causing erosion of nesting sites is now the most serious threat to the long-term survival of the Bermuda Petrel at its current nesting sites and has provided the impetus to establish a more secure breeding site elsewhere (Carlile et al 2012).…”