Artificial lights at night cause high mortality of seabirds, one of the most endangered groups of birds globally. Fledglings of burrow-nesting seabirds, and to a lesser extent adults, are attracted to and then grounded (i.e., forced to land) by lights when they fly at night. We reviewed the current state of knowledge of seabird attraction to light to identify information gaps and propose measures to address the problem. Although species in families such as Alcidae and Anatidae can be grounded by artificial light, the most affected seabirds are petrels and shearwaters (Procellariiformes). At least 56 species of Procellariiformes, more than one-third of them (24) threatened, are subject to grounding by lights. Seabirds grounded by lights have been found worldwide, mainly on oceanic islands but also at some continental locations. Petrel breeding grounds confined to formerly uninhabited islands are particularly at risk from light pollution due to tourism and urban sprawl. Where it is impractical to ban external lights, rescue programs of grounded birds offer the most immediate and employed mitigation to reduce the rate of light-induced mortality and save thousands of birds every year. These programs also provide useful information for seabird management. However, these data are typically fragmentary, biased, and uncertain and can lead to inaccurate impact estimates and poor understanding of the phenomenon of seabird attraction to lights. We believe the most urgently needed actions to mitigate and understand light-induced mortality of seabirds are estimation of mortality and effects on populations; determination of threshold light levels and safe distances from light sources; documentation of the fate of rescued birds; improvement of rescue campaigns, particularly in terms of increasing recovery rates and level of care; and research on seabird-friendly lights to reduce attraction.

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

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