INTRODUCTION 



in this case, familiarity breeds love. Many helminthologists find the 

 diffuse kidneys of intestinal worms not only profoundly interesting but 

 objects of considerable beauty. But this, like the aesthetic pleasure 

 derived from pictures painted by Picasso, although real enough, is an 

 acquired taste. 



Birds are no more victimised by parasites than any other class of 

 vertebrates but, except for the fish Hce (Copepoda) and a few other 

 exclusively marine animals, they are attacked by representatives of 

 most of the well-known parasitic groups, ranging from unicellular 

 Coccidia to the more familiar cuckoos. 



The ordinary "normal" bird supports a large number of both 

 relatively harmless and harmful parasites (see fig. i), the presence of 

 which is largely unsuspected by naturahsts as a whole. In fact, it 

 comes as rather a shock to the ornithologist as well as the bird lover to 

 discover the ills to which avian flesh is heir. 



Their feathers are eaten and sometimes completely destroyed by 

 lice and mites. The superficial layers of their skin and its waxy exuda- 

 tion are devoured by certain flies. Mites and tongue-worms also 

 invade the nasal cavities, the bronchial tubes, air sacs and lungs and 

 feed upon their secretions. Fleas, hce, mosquitoes, midges, bugs, 

 leeches and ticks suck their blood from outside. Protozoa (one-celled 

 organisms), such as the malaria parasite, destroy the red blood cor- 

 puscles from inside the body. Other Protozoa, the trypanosomes, 

 are found in the bone-marrow and lymph vessels, and flagellates 

 swarm in the crop and mouth. Varieties of worms are located in almost 

 every organ of the body, the subcutaneous tissues, the muscles, the 

 eye, the brain, the trachea, liver, kidneys, gall-bladder, bile-duct, 

 reproductive organs and the ahmentary canal. Leeches fix themselves 

 inside the vent and sometimes in the throat-pouches of pelicans. 



Moreover, there is not only a large variety of species of parasites 

 which can attack birds, but sometimes very large numbers of one sort 

 of parasite are found in a single individual. Thus, over 10,000 

 nematode worms are recorded from the intestine of a grouse and more 

 than 1 ,000 feather lice from the plumage of a single curlew. Shipley 

 was so impressed by the variety and number of their parasites that he 

 exclaimed, " They are not only birds but aviating zoological gardens." 

 The life history of the malaria parasite of man, perhaps the most 

 important discovery in the whole field of human parasitology, was 

 worked out on a closely related species from wild birds. The hfe-cycle 



FFC— B 



