Studies on three congeneric species of fleas (Siphonaptera) from the nests of Delichon urbica urbica in England

The house martin D.u.urbica builds an enclosed dome shaped nest of mud under overhangs on cliffs or buildings. Three species of flea, Ceratophyllus hirundinis, C.farreni and C.rusticus are commonly found in these nests. The relationship between these three congeneric and monoxenous species that permits coexistence on the same host and nest was investigated. This study comprised a detailed examination of some of the abiotic and biotic factors which might influence the distribution and abundance of these three species, as well as those factors which may control inter- and intra-specific competition. To achieve this the following aspects were examined. 1) The effect of different geographical localities within England and of nest site and nest characteristics on the flea community was investigated. Nests were collected and the numbers of each species from each nest recorded as were the characteristics of each nest. Analysis showed that the numbers of each species were often positively correlated suggesting that little inter-specific competition at the densities encountered was taking place. It further suggested that conditions suitable for one specie were also suitable for the others. Evidence of differing responses to the wall material to which the nests were attached and the type of nest lining material was obtained. All three species were more abundant in nests attached to brick or painted dash than those on faced stone surfaces. All three species were encountered in nests taken from cliffs where rougher surfaces may present more sheltering places. 2) Nest environment (temperature and relative humidity) was measured in nests occupied by martins and throughout the winter months when the nests were unoccupied. In occupied nests the environment is controlled by the martins. During the winter months the environment is close to ambient although changes in temperature are buffered by the nest wall and lining material. Consequently overwintering fleas are exposed to a wide range of environmental conditions. 3) Flea emigration was examined by placing sticky traps around nests, by passing sticky cards over the front of nests and by netting and "defleaing" martins. Only two fleas were caught on the traps around the nests although they were left in position for two years and none on the cards passed over the nests. A few fleas were removed from the bodies of the martins. It is concluded that colonisation of new nests and re-colonisation of existing nests relied on transportation on the martins and that new nests were likely to be colonised by only a few fleas. 4) Survival of adult fleas in the absence of the martins was investigated with different nest lining materials at different temperatures and relative humidities. At least 50% of the fleas survived a range of temperatures and humidities over several months. However, when offered a blood meal not all individuals fed. Further, not all individuals would mate. Hence, despite surviving for long periods, not all fleas contribute to future generations. 5) Metabolic activity was investigated at different temperatures using a Gilson Respirometer. Activity of each species was monitored in a flea activity monitor. The respirometry showed that there was considerable variation in the respiration rates both between and within species and between autumn and spring. Males had a significantly higher respiration rate than females. The activity monitor showed C.rusticus to be less active than the other two species with females overall more active than males. 6) Population dynamics was studied by the collection of nests at different times of the martin breeding season. Each species will only reproduce while the nest is occupied by the martins. The number of broods the martin had appeared to be of no importance in determining the breeding cycles of the fleas as long as the nest was used regularly for roosting. Data on the feeding rate, amount of blood taken and defaecated and the effects of density on these was obtained by offering each species a blood meal on the ear of a rabbit. Females took significantly more blood than males. At the densities tested little effect on feeding behaviour was observed. Using Bob White Quail, which was the least efficient species at removing fleas, the effects of different nest lining materials on the length of time the fleas spent feeding was examined. The results showed that in the presence of feathers a sigificantly shorter time was spent feeding with the longest when no lining material was present.