Abstract
Since the open-ocean subpolar Atlantic is amongst the most predictable regions in the world, our results hold promise for predicting the general production to seabird populations over a large geographical region adjacent to the northern North Atlantic and the Arctic Mediterranean. Colonies of black-legged kittiwakes Rissa tridactyla in the North Atlantic have declined markedly since the mid-1990s, partly due to repeatedly failing breeding seasons. We show a close link between the breeding success of a kittiwake colony in the Faroe Islands and the subpolar gyre index. Successful breeding follows winters with an expanded subpolar gyre and, by inference, increased zooplankton abundances southwest of Iceland. The environmental conditions in the northwestern Atlantic during the non-breeding and pre-breeding seasons might therefore be important. Furthermore, the subpolar gyre dynamics might influence the local food abundance on the Faroe shelf during the breeding season.
Highlights
The populations of black-legged kittiwakes Rissa tridactyla, terns, and auks have declined markedly in the Northeastern (NE) Atlantic and adjacent shelf seas during the last 25 years
The breeding success of the Faroe kittiwakes is significantly correlated to the pre-breeding food abundance southwest of Iceland, proxied by the Frontal position (r = 0.71, p < 0.001 for 1993–2013, Figure 3A)
The breeding success is highly variable, and the peaks in 1994–1995, 2000–2001, 2009, and 2012 are all associated with deep convection events
Summary
The populations of black-legged kittiwakes Rissa tridactyla (hereafter kittiwake), terns, and auks have declined markedly in the Northeastern (NE) Atlantic and adjacent shelf seas during the last 25 years. This is partly due to large declines in chick production, referred to as the breeding success (Frederiksen et al, 2007a; Descamps et al, 2017, in press). The advent of geolocators has revealed that many seabird species from the NE Atlantic occupy northwestern (NW) Atlantic waters during the non-breeding period, likely due to better food availability during winter (Frederiksen et al, 2012). Processes impacting the food abundance in the NW overwintering region (Bogdanova et al, 2011) could have a profound impact on several seabird populations due to “carry-over effects” on the breeding success during the following summer, and due to the high mortality during the non-breeding season (Harris et al, 2005)
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