Sympatric and allopatric combinations of hen fleas and great tits: A test of the local adaptation hypothesis

To test whether allopatric nest parasites differ from sympatric ones in their effect on various life history traits of their avian host, I designed a cross-transfer experiment in which hen fleas (Ceratophyllus gallinae) were exchanged between great tit (Palus major) nests in two geographically widely separated areas. In neither of the areas did allopatric fleas influence body mass, tarsus length, wing length, duration of nestling period or mortality in great tit nestlings more severely than did sympatric fleas. Duration of incubation was also similar among females independent of experimental treatment. This lack of difference between allopatric and sympatric fleas is hypothesized to reflect the comparative harmlessness of hen fleas for their hosts.