FLEAS III 



The bird may have picked it up from the nest of its fosterparents 

 (Plate XXXVIIIb) or during migration along the same route as 

 wheatears, pipits or wagtails. 



Both C. garei and C. borealis have, fundamentally, a circumpolar or 

 alpine-boreal distribution not unlike that of C. vagabunda (p. 87), but 

 C. borealis has apparently become confined to inaccessible islands and 

 the European Alps, whereas C. garei is established over quite a wide area. 

 It seems possible that these species come into direct competition with 

 each other when they meet in one area and that C. garei is eventually 

 successful and replaces C. borealis. At the same time one wonders if in 

 turn C. garei is slowly being ousted by C. gallinae for in the past it may well 

 have occupied all birds' nests, wet and dry. One can foresee the day 

 when it will be forced to occupy a more and more restricted habitat 

 until it has become a very rare flea, entirely confined to ducks breeding 

 in marshy ground. 



THE HEN FLEA, C. galHnae and the grow flea, C. rossittensis (Plates 

 XIV, XVI, and Map 3). In Britain C. gallinae is the commonest 

 and the best known of all the bird fleas. It has been recorded from 

 65 avian hosts in this country and has been found as a straggler on 

 a number of mammals, such as rats, bats, moles, mice, squirrels and 

 stoats. Ducks and geese, however, seem immune to its attacks. It is the 

 flea par excellence of dry aerial nests and occasionally is seen in numbers 

 which rival the house-martin fleas. Apart from starlings and sparrows 

 it greatly favours the nests of owls and the crow family. At least once it 

 has been counted in thousands in a single nest. The general behef is 

 that C. gallinae was originally a tit flea and certainly it is exceedingly 

 common in nests of blue tits and great tits. In the domestic fowl it has 

 found a new host which suits it admirably, for hen coops are relatively 

 dry and the hens live in close proximity to one another. Sometimes their 

 sleeping quarters are teeming with this flea and continual scratching 

 by the birds has a deleterious eflfect on their health and reduces tgg 

 laying. 



In relatively recent years C. gallinae has been introduced into the 

 eastern United States (see p. 93) where it infests poultry as well as 

 wild birds. In the western United States the domestic fowl is para- 

 sitised by an indigenous flea from wild birds — C. niger. It will be 

 extremely interesting to see if this hardy Christopher Columbus from 

 Europe wiU continue its spread westwards and finish up by ousting the 



