Interrelations Between Seabirds and Introduced Animals 



by 



Robert D. Jones, Jr. 



U.S. Fish and Wildlife Service 



1011 East Tudor Road 

 Anchorage, Alaska 99507 



and 

 G. Vernon Byrd 1 



U.S. Fish and Wildlife Service 



Aleutian Islands National Wildlife Refuge 



Adak, Alaska 



Abstract 



Animals introduced to insular seabird habitats are of both intentional and acci- 

 dental origin. The results of the introductions particularly of herbivores can- 

 not be predicted, but may range from severely destructive to beneficial. Herbi- 

 vores are of both domestic and wild stocks of ungulates, hares, and rabbits. Rats 

 are the most commonly introduced omnivore on a worldwide basis. In Alaska the 

 commonest carnivore introduction has been the red fox ( Vulpes fulva) and arctic 

 fox (Alopex lagopus), and the first of these were made in the early 19th century 

 by the Russian- American Company. These foxes nearly extirpated the Aleutian 

 Canada goose (Branta canadensis leucopareia) from its nesting grounds. Black 

 flies (Simuliidae), which are vectors of avian blood parasites, have been intro- 

 duced to three of the Aleutian Islands. 



The purpose of this paper is to discuss some 

 influences of introduced animals, primarily 

 mammals, on seabirds and their nesting habi- 

 tat, with emphasis on the coasts of Washing- 

 ton, British Columbia, and Alaska. Our dis- 

 cussion focuses on island introductions partly 

 because a large proportion of seabirds choose 

 island nesting sites, and because islands pre- 

 sent ecosystems vulnerable to such in- 

 troductions. 



Flightless animals have no means of immi- 

 gration, hence little probability of colonizing 

 islands. In these circumstances marine birds 

 evolve populations in relatively simple ecosys- 

 tems (Carlquist 1965; MacArthur and Wilson 

 1967), though the degree of simplicity de- 

 pends on several variables, including the is- 

 land's size and its distance from a source of 



'Present address: Hawaiian Islands National Wild- 

 life Refuge, Kilauea, Hawaii. 



immigrants. These systems have achieved 

 ecological homeostasis through reciprocal 

 adaptation over an extended period. Experi- 

 ence has shown that introductions to such 

 systems result in severe perturbations (Odum 

 1971:221). 



The introductions can be categorized as 

 being either intentional or accidental events. 

 Effects of such introductions have varied 

 widely, depending on the type of animal intro- 

 duced, the types of birds present and the habi- 

 tat they occupy, the size and shape of the is- 

 land, the type of nesting area used by the 

 birds, and the status of their populations be- 

 fore the introduction. An example drawn from 

 our Aleutian experience with gallinaceous 

 birds illustrates the interaction of these vari- 

 ables. The dark phase of the arctic fox (Alopex 

 lagopus) was introduced to Adak and Am- 

 chitka islands, both of which had native popu- 

 lations of the rock ptarmigan, Lagopus mutus 



221 



