DENSITY-DEPENDENT PROCESSES IN THE POPULATION DYNAMICS OF A BIRD ECTOPARASITECERATOPHYLLUS GALLINAE

Abstract

The hen flea Ceratophyllus gallinae (Siphonaptera: Ceratophyllidae) is a common ectoparasite in Blue Tit Parus caeruleus nests, whereby adult fleas draw blood from the incubating female host and from the nestlings. Host–parasite interactions are influenced by density-dependent growth of the parasite population, which may result from competitive exploitation or interference between parasite individuals, or from density-dependent host defenses. Understanding density dependence in host–parasite interactions is important for understanding the evolution of parasite virulence and of host defense. Here we investigate density-dependent processes in the dynamics of flea subpopulations. In a first experiment, intended to establish the importance of density dependence in this host–parasite system, the founder density of parasites was manipulated, and reproductive rates of parasites measured. A second experiment was designed to identify the demographic levels at which density dependence arises in the growth of the hen flea population. The experiments show that parasite reproductive rates significantly decrease with increasing founder density. The patterns of egg production, larval production, and adult flea survival suggest that competition between larvae is the main process behind the density-dependent pattern of subpopulation growth. Host mortality, body condition, and blood hematocrit level of the female host and the nestlings were not significantly affected by parasite load, suggesting that adult fleas are not food limited at high densities.