igO SEA-BIRDS 



the parent's throat seems to act as a strainer allowing, as a rule, only 

 semi-digested food to pass, and I have often seen an adult re-swallow 

 larger portions of food which cannot get through. . . . Before it is 

 possible to feed the chick again, the vomiting process must be repeated." 

 (Richdale, 1939, on the royal albatross). 



The North Atlantic petrels are primarily plankton-feeders. Fisher 

 (1952, pp. 409-32) gives a comprehensive list of the foods found in 

 fulmars' stomachs; it includes remains of birds' carcases, carrion of 

 bear, walrus, seal and whale, molluscs (cephalopod beaks and lenses 

 are found universally in petrel stomachs), crustaceans, and coelenter- 

 ates especially. All petrels greedily eat oily matter and fat, especially 

 that from live and dead whales. 



Fulmars have greatly increased in the North Atlantic during the 

 last two hundred years, and, as discussed in a preceding chapter 

 (p. 105), this increase is almost certainly related in the first century 

 to the offal supplied by northern whaling (in which right whales were 

 flensed at ship's side), and in the second century to the continuous 

 vast output of fish offal thrown into the sea by the modern fleets of 

 power-driven trawlers and fishing boats in deep water of the Contin- 

 ental Shelf; this waste is greedily devoured by fulmars which attend 

 the trawling grounds in their thousands today, and every day through- 

 out the year. 



Planktonic Crustacea are responsible for the red, orange or yellow 

 colour of the oil which petrels eject when disturbed. This waxy oil, 

 like cod-liver oil, is rich in vitamin A; it also contains vitamin D, and 

 is similar in character to the oil from the preen-glands of birds.* 

 Its composition is different from that of the oil of the marine organisms 

 on which petrels feed, and it is certainly (Matthews, 1949, 1950) a 

 stomach gland secretion and not an indigestible residue of food. It is 

 generally believed that the very young chick at first is fed wholly 

 on this clear oil (Roberts, 1940, p. 168), but as it grows older the crop 

 of the young bird is found to contain more solid food, including recog- 

 nisable portions of cephalopoda, Crustacea, small fishes, etc. Vegetable 

 debris is often present in small quantities, especially in the stomach of 

 the adult, such as grass, sorrel and other plant scraps, evidently 

 picked up on the breeding ground. 



*Fisher (1952) has no doubt that the tubular nostrils are an anatomical adaptation 

 for preening, since they are found only on birds which produce stomach-oil; and 

 that there is a discharge of oil through the nostrils in preening operations. Certainly 

 after vomiting oil through the mouth, fulmar and storm-petrel will be found to have 

 oil exuding from the nostrils. 



