FLEAS 89 



In the Alps the host of C. vagabunda is the alpine chough {Pyrrhocorax 

 graculus) and one may hazard the guess that choughs were once its true 

 hosts all over the Palaearctic region which they then occupied. When 

 the ice began to retreat the choughs, which were adapted to the cold 

 conditions were only able to survive in the extreme north or in the 

 mountains where the climate suited them, and where they escaped the 

 intense competition from certain other species better adapted to the 

 warmer conditions. Our chough [Pyrrhocorax pyrrhocorax) which is not 

 confined to mountains has managed to survive precariously in a few 

 areas in Britain on remote cliffs. Its fleas are not known. The bird 

 possibly responsible for the present decline of the chough is the jackdaw 

 with which it comes into direct competition. This is the bird most 

 likely to prove a suitable host for a chough flea and it is interesting to 

 find C. vagabunda parasitising the jackdaw in Britain, even far inland. 

 The number of records of this flea from all birds in the British Isles is 

 twenty-four, no less than five of which are from the jackdaw. The next 

 largest number of records from one host is from the herring-gull (4) and 

 shag (4). It is possible that this boreal species of flea will once again 

 spread gradually all over the Palaearctic region, having firmly estab- 

 Ushed itself on the chough's successor. 



Origins and Evolution of British Bird Fleas 



There are approximately one thousand different species of mammal 

 fleas known in the world to-day, but there are only between fifty and 

 sixty bird fleas. It is thought that the bird fleas have been derived 

 from the mammal fleas, in relatively recent times. This can be 



Map I . Distribution of the three commonest fleas from the house-martin in Britain. 

 • : Ceratophyllus hirundinis ; -\- : C.farreni; A : C. rustictis 



Map 2. Distribution of the duck flea, C. garei, and boreal flea, C. borealisy in Britain. 



• : C. garei ; © : C. borealis 



Map 3. Distribution of the hen flea, C. gallinae, in Britain. (The concentrations of 



records denote the chief collecting areas of five well-known collectors, Rothschild, 



Waterston, Newstead, O'Mahony and Britten.) 



Map 4. Distribution of the moorhen flea, Dasypsyllus gallinulae, and the shearwater 



flea, OrmthopsyUa laetitiae, in Britain. 

 • : -D. gallinulae \ >J<: 0. laetitiae 



