Expanding the marine range of the endangered black-capped petrelPterodroma hasitata: Occurrence in the northern Gulf of Mexico and conservation implications

Abstract

The black-capped petrel (Pterodroma hasitata) is an endangered seabird endemic to the western north Atlantic. Although estimated at ~ 1,000 breeding pairs, only ~ 100 nests have been located at two sites in Haiti and three sites in the Dominican Republic. At sea, the species primarily occupies waters of the western Gulf Stream in the Atlantic and the Caribbean Sea. Due to limited data, there is currently not a consensus on the marine range of the species. There are several maps in use for the marine range of the species and these differ with respect to the north, south, and eastward extent of the range. None of these maps, however, includes the Gulf of Mexico. Here, we report on observations of black-capped petrels during two vessel-based survey efforts throughout the northern Gulf of Mexico from July 2010 - July 2011, and from April 2017 - September 2019. During the 558 days and 54.7 km of surveys from both efforts we tallied 40 black-capped petrels. Most observations occurred in the eastern Gulf, although birds were observed over much of the east-west and north-south footprint of the survey area. Predictive models indicated that habitat suitability for black-capped petrels was highest in areas associated with dynamic waters of the Loop Current, similar to habitat used along the western edge of the Gulf Stream in the western north Atlantic. We suggest that the range for black-capped petrels be modified to include the entire northern Gulf of Mexico although distribution may be more clumped in the eastern Gulf and patchier elsewhere. It remains unclear, however, which nesting areas are linked to the Gulf of Mexico.

Migration, breeding location, and seascape shape seabird assemblages in the northern Gulf of Mexico

“…The northern Gulf of Mexico (which contains the Exclusive Economic Zone of the USA; nGoM) provides important habitat for a broad range of fauna [1,2], one of the least studied components of which has been seabirds (but see [3]). This region supports a wide array of seabirds in terms of taxonomic diversity, geographic origin, foraging behavior, and conservation status [4]. For example, the breeding origins of seabirds that occur in the nGoM include six distinct geographic areas that span ˜120 degrees of latitude and both sides of the Atlantic; the northern Gulf coast, the continental interior of North America, the northeast coast of North America, the Caribbean, the eastern North Atlantic, and the western South Atlantic [4].…”

“…This region supports a wide array of seabirds in terms of taxonomic diversity, geographic origin, foraging behavior, and conservation status [4]. For example, the breeding origins of seabirds that occur in the nGoM include six distinct geographic areas that span ˜120 degrees of latitude and both sides of the Atlantic; the northern Gulf coast, the continental interior of North America, the northeast coast of North America, the Caribbean, the eastern North Atlantic, and the western South Atlantic [4]. The unique annual cycles and migration patterns of species from each of these breeding origins result in a dynamic assemblage of seabirds, some of which occupy one, often spatially expansive, habitat type (e.g., pelagic or nearshore), while others occupy a broad range of habitats.…”

“…Given our interest in the contribution of species breeding predominantly outside of the nGoM to the nGoM's seabird assemblage and a strong correlation (Spearman's rho: -0.871) between bathymetry and distance to land, we did not include distance to land in our analysis. In light of the occurrence of migratory seabirds in the nGoM [4] and the potential seasonal movements of non-migratory species, we included month as a covariate in the analysis. We used the Tweedie distribution with a log link function to fit all models and applied thin-plate splines to all covariates, excluding the spatial smooth [54,55].…”

“…We also considered if the identified associations suggested links to other fauna, such as fish, that could infer community relationships. Our characterization of distinct seabird assemblages is the first of its kind for the nGoM and identifies important features shaping seabird assemblages, potentially informing future research, development, and monitoring in a region facing substantial pressure from both natural and anthropogenic stressors [4].…”

“…Given the lack of survey and research attention on seabirds in the nGoM compared to many other marine regions and the potential vulnerability of seabirds there to a wide range of environmental and anthropogenic stressors (e.g., offshore energy production, heavy shipping traffic, potential aquaculture) [4,25], we sought to identify and characterize the structure of distinct seabird assemblages in offshore waters. We used observations from vessel-based surveys collected as a part of the Gulf of Mexico Marine Assessment Program for Protected Species (GoMMAPPS), which have not previously been used to characterize seabird assemblages in the nGoM.…”