114 SEA-BIRDS 



largest puffinry, which is on a broad ledge exactly half-way down the 

 incredible cliff of the Kame. 



Occasionally (and certainly not very importantly) fish have been 

 known to prey upon sea-birds. W. E. Glegg (1945, 1947), who has 

 compiled records of aquatic animals preying upon birds, lists the 

 angler-fish as having taken scoter, merganser, cormorant, Manx 

 shearwater, great northern diver, gulls (including the herring-gull), 

 razorbill and guillemots. He also lists the cod as having taken cormor- 

 ant, Briinnich's guillemot and black guillemot; angel-fish and pike 

 as having taken cormorant; unknown fish as having taken the white- 

 winged black tern, and what were probably fish as having taken the 

 Sandwich tern and the African grey-headed gull. 



The ectoparasites of sea-birds are many. They include several 

 highly specialised mites, many mallophaga or biting-lice, ticks and some 

 fleas. There is no evidence whatsoever that any of them significantly 

 control the numbers of their host, nor, indeed, any evidence that any 

 of them carry diseases.* 



Very little is known about the endoparasites of sea-birds; they 

 have many species of cestodes, nematodes and trematodes, and some 

 protozoa. Extremely little is known about the bacterial and virus 

 parasites of birds, though it appears that of all the internal parasites 

 these are the only ones likely to affect natural populations. Recently 

 considerable attention has been drawn to the virus diseases of sea- 

 birds by J. A. R. Miles, who has identified a virus epizootic of the 

 Manx shearwater which he calls puffinosis (Miles and Stoker, 1948). 

 This disease kills young Manx shearwaters in the crowded Pembrokeshire 

 colonies; the colony on Skokholm, judging from ringing records, 

 is usually between 10,000 and 15,000 birds and that on Skomer double. 

 In some years "many hundreds" of young Manx shearwaters are found 

 dead, but there is no evidence that the disease materially affects the 

 population. (Surrey-Dane, Miles and Stoker, 1953). 



The most important sea-bird disease so far identified is undoubtedly 

 psittacosis (a form of ornithosis) which, in the early 1930's, spread 

 through the vast population of the fulmars nesting in the Faeroes and 

 Iceland. The arguments of R. K. Rasmussen, who first identified the 

 disease, and J. A. R. Miles, who has subsequently studied the problem 

 (Miles and Shrivastav, 1951), are summarised in Fisher's The Fulmar 



*In 1949 Lockley found hundreds of fledgeling puffins dying of excessive blood- 

 sucking by the common red mite [Dermanyssus gallinae) on the islet of Burhou, Channel 

 Islands. 



