INTERRELATIONS BETWEEN SEABIRDS AND INTRODUCED ANIMALS 223 



ported for sheep develops in some cases. 

 Bailey et al. (1933) speculated that nests of 

 the snow goose (Anser caerulescens) were de- 

 stroyed by reindeer or their herdsmen in the 

 Point Barrow area. 



The destruction of vegetation by introduced 

 rabbits and hares has been documented for 

 many areas in the world. This destruction has 

 often extended to seabirds. Perhaps the most 

 dramatic example occurred on Laysan Island 

 in the Hawaiian archipelago, where rabbits of 

 unknown species were introduced in 1903. Ac- 

 cording to Warner (1963) it took less than 20 

 years for the rabbits to remove every green 

 plant but three patches of Sesuvium portu- 

 lacastrum. The Laysan duck (Anas laysanen- 

 sis) was brought perilously close to extinc- 

 tion. The rabbits were eliminated in the 

 1920's, and the population of ducks increased 

 to over 600 by 1963, a figure thought to ap- 

 proximate the predisturbance population. 



European hares (Lepus europaeus) were in- 

 troduced on Smith, San Juan, and Long is- 

 lands, in Washington. On Smith Island, these 

 burrowing animals apparently grazed nearly 

 all the succulent vegetation close to the 

 ground. By 1924, their burrows riddled the 

 bluffs, causing them to cave into the ocean 

 (Couch 1929). Couch found no seabirds nest- 

 ing on the island, but found numerous tufted 

 puffins (Lunda cirrhata) present on the bluffs, 

 but not nesting. A removal campaign was di- 

 rected against the hares in 1924 and in a few 

 years they were gone. Smith Island now sup- 

 ports nesting pelagic birds (D. Manuwal, per- 

 sonal communication). 



Accounts of hare and rabbit introductions 

 to islands are legion, but not all such introduc- 

 tions have drastically affected seabirds. 

 Manana Island, Hawaii, is such a case. 

 Tomich et al. (1968) believed that introduced 

 rabbits (Oryctolagus cuniculas) were not even 

 indirectly detrimental to the nesting noddies 

 (Anous tolidus) and sooty terns (Sterna fus- 

 cata). In some situations, introduced lago- 

 morphs have been credited with benefiting 

 seabirds. Lockley (1942) suggested that 

 rabbits helped to open new breeding colonies 

 of manx shearwaters (Puffinus puffinus} at 

 Skomer and in west Wales in general. In 

 Alaska rabbits were introduced to Middleton 

 Island in 1952 (Rausch 1958) and to Ananiu- 

 liak Island at an earlier unrecorded date. Both 



have developed sustaining populations in the 

 presence of large seabird populations without 

 measurable effect on the birds. On Ananiuliak 

 glaucous- winged gulls (Lams glaucescens) 

 have been observed feeding on rabbits (W. S. 

 Laughlin, personal communication). 



Invertebrates have been introduced on 

 three islands in the Aleutians. The black fly 

 (Simulium sp.) reached Adak by 1958, 

 Shemya by 1964, and Amchitka in connection 

 with activities of the Atomic Energy Commis- 

 sion in 1968. Apparently the insects were 

 transported on jet aircraft. The pest appears 

 well established on Adak, but its status on the 

 other two islands is uncertain. Like the mos- 

 quito, the female black fly sucks blood from 

 warm-blooded animals, and in the process be- 

 comes the vector of a Leucocytozoan blood 

 parasite of birds. In years of black fly abun- 

 dance at Seney (Michigan) National Wildlife 

 Refuge the blood parasite has been respon- 

 sible for reproductive failure in Canada geese 

 (Branta canadensis; Sherwood 1968). If black 

 fly problems reach such a scale in the Aleu- 

 tians, the parasites might prove limiting to 

 pelagic birds as well as to waterfowl. Winds, 

 for which the Aleutian region is famous, con- 

 stitute a limiting factor for obligate blood- 

 feeding Simuliids and may control the 

 severity of this problem. 



Predatory Animals 



The list of introduced animals that prey on 

 seabirds is extensive. Often several animals 

 have been introduced to the same island. For 

 example, in 1951 Amchitka Island in the 

 Aleutians supported populations of feral dogs 

 (Cam's familiaris) and cats (Felis catus), rats 

 (Rattus norvegicus), and arctic fox. Their 

 presence resulted from three of the usual 

 sources of predator introductions: escape of 

 pets, escape from visiting ships (and aircraft), 

 and commercial introductions. Add introduc- 

 tions to control pests, such as that of the mon- 

 goose (Herpestes auropunctatus) to the 

 Hawaiian Islands, and only one source re- 

 mainsthe desire of man to improve on na- 

 ture. In the Aleutians this impulse has taken 

 the more innocuous form of fish and plant in- 

 troductions, such as rainbow trout (Salmo 

 gairdneri) on Adak and Shemya, and trees 



