Responses of Pelagic Cormorants (Phalacrocorax pelagicus) to Marine Traffic and Bald Eagles (Haliaeetus leucocephalus) in Barkley Sound, British Columbia

Abstract

Key words: Bald Eagle, Barkley Sound,British Columbia, decline, disturbance, Haliaee-tus leucocephalus, marine traffic, Pelagic Cormo-rant, Phalacrocorax pelagicus, set-backIn Barkley Sound, British Columbia, PelagicCormorants (Phalacrocorax pelagicus), while for-merly abundant (Vermeer and Rankin 1984),have suffered massive declines of up to 85%since 1969 (Carter and others 2007). Thisdecline is thought to be due in part todisturbance by humans and Bald Eagles (Ha-liaeetus leucocephalus) (Chatwin and others 2002;Carter and others 2007). In an attempt toinvestigate the causes of this decline, weundertook a brief study of Pelagic Cormorantswithin Barkley Sound during the nestingperiod in the summer of 2011.Nesting birds are vulnerable to disturbancefrom predators and human interference (Burgerand Gochfeld 1994; del Viejo and others 2004).Disturbance during the nesting period cancause increased stress and behavioral responses,such as flight behavior or nest avoidance, whichmay eventually lead to increased nest preda-tion, thermal shock in eggs, decline in thebreeding success of individuals, and a decreasein the density of breeding pairs (Le Corre andothers 2009). Seabirds are especially vulnerable,as many are relatively long-lived and may bemore inclined to abandon a given breedingattempt and defer breeding until future oppor-tunities (Stearns 1976).Motorized boats have been shown to disturbseabirds in more than 1 study (Burger 1998;Rodgers and Schwikert 2002), and it has been