Foraging areas, offshore habitat use, and colony overlap by incubating Leach’s storm-petrels Oceanodroma leucorhoa in the Northwest Atlantic

Abstract

Despite their importance in marine food webs, much has yet to be learned about the spatial ecology of small seabirds. This includes the Leach’s storm-petrel Oceanodroma leucorhoa, a species that is declining throughout its Northwest Atlantic breeding range. In 2013 and 2014, we used global location sensors to track foraging movements of incubating storm-petrels from 7 eastern Canadian breeding colonies. We determined and compared the foraging trip and at-sea habitat characteristics, analysed spatial overlap among colonies, and determined whether colony foraging ranges intersected with offshore oil and gas operations. Individuals tracked during the incubation period made 4.0 ± 1.4 day foraging trips, travelling to highly pelagic waters over and beyond continental slopes which ranged, on average, 400 to 830 km from colonies. Cumulative travel distances ranged from ~900 to 2,100 km among colonies. While colony size did not influence foraging trip characteristics or the size of areas used at sea, foraging distances tended to be shorter for individuals breeding at the southern end of the range. Core areas did not overlap considerably among colonies, and individuals from all sites except Kent Island in the Bay of Fundy foraged over waters with median depths > 1,950 m and average chlorophyll a concentrations ≤ 0.6 mg/m3. Sea surface temperatures within colony core areas varied considerably (11–23°C), coincident with the birds’ use of cold waters of the Labrador Current or warmer waters of the Gulf Stream Current. Offshore oil and gas operations intersected with the foraging ranges of 5 of 7 colonies. Three of these, including Baccalieu Island, Newfoundland, which supports the species’ largest population, have experienced substantial declines in the last few decades. Future work should prioritize modelling efforts to incorporate information on relative predation risk at colonies, spatially explicit risks at-sea on the breeding and wintering grounds, effects of climate and marine ecosystem change, as well as lethal and sub-lethal effects of environmental contaminants, to better understand drivers of Leach’s storm-petrel populations trends in Atlantic Canada.

Year-round movements of sympatric Fork-tailed (Oceanodroma furcata) and Leach's (O. leucorhoa) storm-petrels

“…In comparison, Hedd et al. () reported that Leach's Storm‐Petrels in the Atlantic Ocean ranged up to 830 km from breeding colonies during incubation. Other small Procellariiform seabirds are also known to forage over large areas when breeding (Pollet et al.…”

Breeding population decline and associations with nest site use of Leach’s Storm-Petrels on Kent Island, New Brunswick from 2001 to 2018

“…Another potential cause for declining population trends is strandings associated with light pollution from the offshore oil and gas industry (Wiese et al 2001, Montevecchi 2006, Ronconi et al 2015. However, foraging ranges of storm-petrels nesting at colonies located in northern Nova Scotia and the east coast of Newfoundland overlap with offshore oil and gas platforms, yet the foraging range of Kent Island storm-petrels does not (Hedd et al 2018), suggesting that this source of potential mortality is not a factor for the Kent island colony. Chronic oil spills within seabird foraging ranges also pose risk of increased mortality (Wiese and Robertson 2004).…”

Marine hotspots of activity inform protection of a threatened community of pelagic species in a large oceanic jurisdiction

“…Some breeding species such as Brown Skua Catharacta antarctica, Broad-billed Prion Pachyptila vittata or MacGillivray's Prion Pachyptila macgillivrayi were not included in our hotspot assessment because these species have only been tracked with Global Location Sensing (GLS) loggers, which have too large uncertainty for our analysis (Dias et al, 2017;Phillips et al, 2004). Other small seabird species, notably storm-petrels, diving petrels and terns, have not been tracked so far, and while terns likely remain within the EEZ during the breeding season, storm-petrels are very mobile and may utilize areas far away from their breeding grounds (Hedd et al, 2018;Oppel et al, 2018). The absence of data for smaller species may result in an overemphasis of existing data, such as the hotspots identified from Sooty Albatross tracking data in autumn, which may be due to the preference of a small number of individuals and treated with caution.…”