Changing winter diet of Thick-billed Murres (Uria lomvia) in southwest Greenland, 1990s versus 2010s

Southwest Greenland constitutes an internationally important wintering area for seabirds, including Thick-billed Murres (Uria lomvia (Linnaeus, 1758)), but their prey may be affected by the general warming of this sub-Arctic region. We compared murre diet collected in winter in the 1990s and in the 2010s around Nuuk, Greenland. Fish made up 36% of the diet (wet mass) and crustaceans 63% in the 1990s, changing to 22% and 78% in the 2010s, respectively. Capelin (Mallotus villosus (Muller, 1776)) was the dominant fish species, and the smaller contribution in the 2010s coincided with declining densities of capelin around Nuuk. The crustaceans were dominated by two krill species (Meganyctiphanes norvegica (M. Sars, 1857) and Thysanoessa inermis (Kroyer, 1846)). However, M. norvegica was only important in the 2010s (51% wet mass), while T. inermis was dominating the 1990s with 62% wet mass and only 23% in the 2010s. The dominance of M. norvegica in the 2010s confirmed our expectations of a gradual 'borealization' of this region due to the generally warming sub-Arctic. The smaller contribution of fish in the diet may also support the hypothesis of deteriorating winter conditions for murres. Apart from the diet, plastic was found in 15% of the birds and 53% had parasitic nematodes. Key words: seabird winter diet, Thick-billed Murre, Uria lomvia, southwest Greenland, borealization, krill, capelin, Mallotus villosus. Si le sud-ouest du Groenland constitue une aire d'hivernage d'importance internationale pour les oiseaux marins, incluant le guillemot de Brunnich (Uria lomvia (Linnaeus, 1758)), le rechauffement general de cette region subarctique pourrait avoir une incidence sur leurs proies. Nous comparons les regimes alimentaires hivernaux de guillemots durant les annees 1990 et 2010 dans les environs de Nuuk (Groenland). Les poissons constituaient 36 % (masse humide) de leur alimentation et les crustaces, 63 %, dans les annees 1990, ces proportions passant a 22 % et 78 %, respectivement, durant les annees 2010. Le capelan (Mallotus villosus (Muller, 1776)) etait l'espece de poisson dominante, et le plus faible pourcentage de poissons dans les annees 2010 coincide avec des densites de capelans reduites aux environs de Nuuk. Parmi les crustaces consommes, deux especes de krill (Meganyctiphanes norvegica (M. Sars, 1857) et Thysanoessa inermis (Kroyer, 1846)) dominaient. Toutefois, M. norvegica n'etait important que dans les annees 2010 (51 % masse humide), alors que T. inermis etait dominant dans les annees 1990 (62 % masse humide, contre seulement 23 % durant les annees 2010). La predominance de M. norvegica dans les annees 2010 confirme nos predictions d'une <> progressive de cette region decoulant du rechauffement general de la region subarctique. La diminution de la proportion des poissons dans l'alimentation pourrait egalement appuyer l'hypothese de la deterioration des conditions hivernales pour les guillemots. Du plastique a egalement ete retrouve dans 15 % des oiseaux, et 53 % etaient parasites par des nematodes. [Traduit par la Redaction] Mots-cles: alimentation hivernale des oiseaux marins, guillemot de Brunnich, Uria lomvia, sud-ouest du Groenland, borealisation, krill, capelan, Mallotus villosus.
Introduction For migratory bird populations, the non-breeding season represents a very long and usually challenging period of their annual cycle, and their survival and subsequent breeding performance are highly dependent [...]