THE ECOLOGY OF THE HEN FLEA CERATOPHYLLUS-GALLINAE AND THE MOORHEN FLEA DASYPSYLLUS-GALLINULAE IN NESTBOXES

1. Populations of fleas from nests of seven species of bird have been measured over a 10-year period. 2. The hen flea is more abundant in nests of tits than of pied flycatcher and redstart. The moorhen flea is more abundant in marsh tit, coal tit, and redstart nests than in pied flycatcher and other tit nests. There is no evidence of competition between the two fleas. 3. The date the birds start nest-building, and/or the length of time the nest is maintained above air temperature, is important in determining population size in the hen flea, but not in the moorhen flea. 4. Hen fleas disperse from overwintering sites in nestboxes early in the birds' breeding season and find hosts mostly among blue tits. The population of hen fleas in pied flycatcher nests is closely related to the number of blue tits breeding, suggesting that the numbers of fleas arriving in the nest is a significant factor in pied flycatchers. 5. There is evidence that another important determinant of population size in both flea species is the number of generations produced in the season, though other factors seem to be limiting at high population densities in the nest. Two generations are the norm in blue tit and great tit nests, but are less frequent in pied flycatcher nests. 6. Factors controlling populations of moorhen fleas remain obscure, though appear to be significantly different from those controlling the hen flea. One-fifth of nests probably do not receive any fertilized females of this species at all, whereas virtually all nests are colonized by the hen flea.