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W. H. DRURY 



than seabirds or that those who overcropped 

 and eliminated the seabirds suffered the 

 consequences. 



Negative Effects 



When a sea-going, commodity-oriented way 

 of life evolved, seabirds were killed in huge 

 numbers for such uses as the plumage trade, 

 fish bait, or rendering into oil (Tuck 1960; 

 Fisher and Lockley 1954). Even the elimina- 

 tion of several colonies e.g., Funk Island, 

 Newfoundland (Tuck 1960); Seal Island, East- 

 ern Egg Rock, Maine (Norton 1921); Muske- 

 get, Massachusetts (Forbush 1929) may 

 have had little effect on the rate of cropping 

 because those who killed off one source could 

 probably seek out another. As the colonial 

 seabirds became scarce they became more 

 valuable, which stimulated more intensive 

 pursuit of the remnants (Butcher 1901, 1904). 



In some places where seabird colonies did 

 not supply a croppable economic resource, the 

 islands were used for alternative crops with at 

 least temporary commodity value (e.g., foxes 

 were introduced in the Aleutian Islands; Bent 

 1919). Large herbivores were introduced to 

 supply meat for island residents (e.g., Saint 

 Matthew Island; Klein 1959), as well as pigs, 

 cattle, sheep, goats, and rabbits on islands in 

 the North Atlantic and southern oceans 

 (many authors). Increases in many seabird 

 populations over the last 75 years have been 

 generally associated with relief from preda- 

 tion by humans such as the fowlers, eggers, 

 and plume hunters of the 19th century. Such 

 relief may have been partly responsible for the 

 increase of North Atlantic gannets, Sula bas- 

 sana, and common murres or guillemots, Uria 

 aalge (Fisher and Vevers 1943, 1944; Cramp 

 et al. 1974). On a smaller scale, several popula- 

 tion increases along the coast of New England 

 have been recorded following the enactment 

 of protective legislation (Butcher 1901, 1904; 

 Norton 1921, 1924; Palmer 1949; Brury 1973). 



Coulson (1974) argued that in addition to re- 

 lief from predation, the explosion of the popu- 

 lation of kittiwakes (Rissa tridactyla) in this 

 century resulted from access to previously un- 

 occupiable breeding sites. Nesting cliffs and 

 buildings suitable for kittiwake nesting are 

 abundant and now protected from egging or 

 fowling. 



Positive Effects 



There can be little doubt that human activi- 

 ties have also had marked positive effects in 

 some cases. For example, Fisher (1952) sug- 

 gested that the North Atlantic fulmar (Ful- 

 marus glacialis) was provided food first by 

 whaling, then by commercial fishing, and that 

 this food allowed the species to increase 

 steadily over the last 3 centuries. 



The worldwide increase of gulls (Lams 

 argentatus, L. fuscus, L. dominicanus, L. ridi- 

 bundus, L. novae-hollandii) has been credited 

 to availability of food from wasteful human 

 garbage disposal (Murray and Carrick 1964; 

 Fordham 1968, 1970; Harris 1964; Harris and 

 Plumb 1965; Kadlec and Brury 1968; Brown 

 1967; Mills 1973; Vermeer 1963). 



It is hard to dismiss the evidence pointing 

 to the impact of human activities on seabird 

 populations during the last 3 centuries. Yet it 

 would be misleading to assume that without 

 man's interference seabird populations would 

 have remained stable. Success in designing 

 programs of protection and population en- 

 hancement must allow for the realities that 

 seabird populations fluctuate inherently, and 

 that secular changes occur regularly in their 

 environment. 



Impact of Natural Events 



Some population changes appear to result 

 from sudden impacts; other changes are 

 gradual. 



Sudden Bisasters 



Gromme (1927) reported windrows of dead 

 murres in the Unimak Pass and Alaska Penin- 

 sula; die-off s of murres in winter storms in the 

 Atlantic and Arctic Oceans were reported by 

 Tuck (1960) and Bement'ev et al. (1968). 



Recently some mass mortalities have been 

 associated with specific causes. Bailey and 

 Bavenport (1972) reported that starvation 

 caused the die-off of common murres in the 

 southern Bering Sea-Bristol Bay area. Foul 

 weather, which apparently inhibited feeding 

 between 19 and 23 April 1970, culminated in 

 an intense storm. Similarly in late winter 1969 

 bad weather in the Irish Sea, combined with 

 strains of molt and perhaps contamination 



