Marine distribution and foraging habitat highlight potential threats at sea for the Endangered Bermuda petrel Pterodroma cahow

Abstract

Marine spatial planning relies on detailed spatial information of marine areas to ensure effective conservation of species. To enhance our understanding of marine habitat use by the highly pelagic Bermuda petrel Pterodroma cahow, we deployed GPS tags on 6 chick-rearing adults in April 2019 and constructed a habitat suitability model using locations classified as foraging to explore functional responses to a selection of marine environmental variables. We defined 15 trips for 5 individuals, ranging from 1−6 trips per bird, that included both short and long foraging excursions indicative of a dual foraging strategy that optimizes chick feeding and self maintenance. The maximum distance birds flew from Bermuda during foraging trips ranged from 61 to 2513 km (total trip lengths: 186−14 051 km). Behaviourally deduced foraging habitat was best predicted at shorter distances from the colony, under warmer sea surface temperature, greater sea surface height, and in deeper water compared to transiting locations; our model results indicated that suitable foraging habitat exists beyond the core home range of the population, as far north as the highly productive Gulf Stream frontal system, and within the territorial waters of both the USA and Canada. Our results are crucial to inform management decisions and international conservation efforts by better identifying potential threats encountered at sea by this globally rare seabird and highlighting jurisdictions potentially responsible for mitigating those threats.

Fine-scale movement data of the endangered Bermuda petrel highlights surface foraging and greater nocturnal flight activity

“…We analysed movement data, activity patterns and diving behaviour to quantify fine scale at-sea behaviours of incubating Bermuda petrels. Similar to previous studies [16, 31], GPS tracking showed that Bermuda petrels undertook extended foraging trips to the NNE of Bermuda, apparently targeting the path of the Gulf Stream, and confirming a reliance on vast oceanic areas for successful foraging as in other Pterodroma petrels [14, 16, 49, 50]. However, in contrast to many other Procellariiformes [10, 27], which can perform dives of considerable duration and depth (see references in [28, 51]), our TDR data suggest that the Bermuda petrel is a surface feeder with limited capacity to dive.…”

“…They were consistent in their departing direction from the colony, as has been observed in the Murphy's petrels (P. ultima) [49], showing a clear preference for the NNE (Fig. 1), targeting the Gulf Stream [16,31]. The pelagic area in which the "search" activity occurred (Fig.…”

“…Overall, this study provides new insights into the foraging behaviour of an endangered gadfly petrel, having potential implications for evaluating the species’ risk of interaction with at-sea anthropogenic activities. For instance, the crossing of vast portions of oceanic areas for foraging, and their nocturnal flight activity makes the species highly vulnerable to the presence and light-driven attraction to oil and gas infrastructures [31], shipping and commercial fishing vessels operating in the western North Atlantic. Particularly, our insights regarding petrels’ surface feeding strategy and scavenging behaviour might help to develop target actions focused to reduce the risk of attraction to fishing boats for feeding on discarded bait or fish offal.…”

Foraging Paths of Breeding Leach’s Storm-Petrels in Relation to Offshore Oil Platforms, Breeding Stage, and Year

“…Failed GPS fixes and the variable delay in achieving successful fixes (10-12 s max) result in inconsistent inter-point timing that is unusable for behavioral classification (see below; Patterson et al, 2008). Hence, trip points were interpolated to achieve consistent inter-point intervals of 2 h (3 h in 2019) by mathematically approximating the longitude and latitude of each point at these standardized times, given the assumption of a straight path between each GPS point (as in Raine et al, 2021). These interpolated data were used for all statistics, except for the calculations of total trip distance and trip duration, as the raw data gave more accurate estimations of these values.…”

Combining tracking with at-sea surveys to improve occurrence and distribution estimates of two threatened seabirds in Peru

“…These versatile models can be fitted to tracking data and/or observational data from surveys together with environmental data to predict the occurrence (when distributional data are provided in presence-absence format) or abundance (when data are provided in absolute numbers) of seabirds as a function of the species’ ecological niche (e.g. Kruger et al 2018, Cleasby et al 2020, Raine et al 2021). SDMs can provide inference of distribution, occurrence, and abundance, the identification of areas of conservation priority, and threat assessments over large spatial and temporal scales, even though tracking and survey data are usually not spatially and temporally comprehensive (e.g.…”