Leapfrog migration and habitat preferences of a small oceanic seabird, Bulwer's petrel (Bulweria bulwerii)

Abstract

Aim Our current understanding of migratory strategies and the reasons for their high 27 variability along the phylogenetic tree remains relatively poor. Most of the hypotheses 28 relating to migration have been formulated for terrestrial taxa; classically, oceanic migrations 29 were considered as merely dispersive due to the scarcity of observations in the open ocean. 30We describe for the first time, the migration strategy of a small seabird, the Bulwer's petrel 31 (Bulweria bulwerii), and provide new insights into the ecology and evolution of long-distance 32 marine migrations. 33 Location Subtropical and tropical Atlantic Ocean. 34Methods Using cutting-edge geolocators, we examined the year-round distribution and at-sea 35 activity patterns of adult Bulwer's petrels sampled at 5 localities throughout its breeding 36 range in the Atlantic: the Azores, Salvages, Canary and Cape Verde archipelagos. We 37 assessed the migratory connectivity of the species and its habitat use at population and meta-38 population scales. 39Results Our results provide the first evidence of an oriented leapfrog migration in oceanic 40 seabirds. Ecological niche models based on breeding-season data effectively predicted that 41 subtropical waters of the South Atlantic would be the preferred habitat for the northern 42 populations of Bulwer's petrels during the non-breeding season. Habitat modelling also 43 highlighted similarities in distributions between the breeding and non-breeding periods for the 44 southern populations. Data on at-sea activity patterns suggested that birds from the northern 45 and southern populations behave differently during the breeding season, as well as in the 46 northern and southern non-breeding ranges during the non-breeding period. 47Main conclusions These results indicate that specific habitat preferences, presumably related 48 to differences in prey availability, explain the observed distributions and hence the pattern of 49 leapfrog migration described for Bulwer's petrel. Our study demonstrates the utility of 50Page 3 integrating diverse tracking data from multiple populations across international boundaries, 51 and habitat modelling, for identifying important areas common to many marine species in the 52 vast oceanic environments. 53 54 Keywords: Activity patterns, Bulweria bulwerii, Bulwer's petrel, capture-mark-recapture, 55 geolocator data, habitat modelling, Macaronesian seabirds, meta-population studies, oceanic 56 migrations. 57Page 4 INTRODUCTION 58Migration is an integral part of the annual life-cycle and life-history of many animal species. 59

A probabilistic algorithm to process geolocation data

“…Their small size and mass (to <1 g) allow a wide range of species to be tracked, and because of the relatively low cost (compared with miniaturized GPS devices), they can be used to track many individuals for multi-population studies (e.g. [10–13]).…”

Biologically informed ecological niche models for an example pelagic, highly mobile species

“…however, nearly all applications of these approaches to pelagic seabirds have focused on individual populations rather than species as a whole; and, few have explored algorithm function for seabirds outside the breeding season (Thiebot et al 2011;Wakefield et al 2011;Oppel et al 2012;Ramos et al 2015).…”

Using globally threatened pelagic birds to identify priority sites for marine conservation in the South Atlantic Ocean

“…bulwerii (Dias et al 2011;Guilford et al 2009;Ramos et al 2015), as well as other species from the South Atlantic. Therefore, these sites are good candidates for MPAs in the South 324 Atlantic, given their high biodiversity value and their potential to benefit a wide number of species from Tristan da Cunha and elsewhere, including many that are threatened.…”