Bermuda Petrel Pterodroma cahow
Version: 2.0 — Published November 16, 2020
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For breeding, Bermuda Petrels utilize small offshore islets exclusively, making their nests in burrows, usually at the end of tunnels. In places where there is topsoil, the birds may excavate these burrows themselves, but most birds now nest in artificial burrows designed to maximize breeding success. All of the breeding islets are composed of aeolian limestone, whose uneven stratification makes it susceptible to fragmentation by heavy seas. Formerly, Bermuda Petrels utilized a wider variety of terrestrial habitats for nesting, and although there are no written accounts detailing precisely the types of habitats occupied, it is clear that the birds excavated burrows in areas with extensive topsoil and trees, as do some of their congeners.
When not at the nest site, Bermuda Petrels inhabit pelagic environments, apparently foraging primarily over deep (> 200 m) water of the continental slope and seaward; there are no reports or records of the species from inshore (littoral waters) and no reports of storm-wrecked birds in terrestrial environments (by contrast, there are nearly 100 such records for Black-capped Petrel). Several pelagic records of Bermuda Petrel are from areas of ocean characterized by temperature breaks or thermoclines over the continental slope, where upwelling of nutrients and higher concentrations of favored prey items would occur. Few data are available at present to adduce characteristics of pelagic waters in which this species most regularly forages, but use of Lotek data-loggers on several individuals per year since 2009 has shown that Bermuda Petrels forage not just in waters adjacent Bermuda or the Carolinas but regularly into the cold waters off New England and Newfoundland, and that many also spend the nonbreeding season in the vicinity of the Azores (21).