T. Eeva et al., EFFECTS OF ECTOPARASITES ON BREEDING SUCCESS OF GREAT TITS (PARUS-MAJOR) AND PIED FLYCATCHERS (FICEDULA-HYPOLEUCA) IN AN AIR-POLLUTION GRADIENT, Canadian journal of zoology, 72(4), 1994, pp. 624-635
Numbers of ectoparasitic blow fly (Protocalliphora azurea) larvae (Dip
tera: Calliphoridae), adult and larval hen fleas, Ceratophyllus gallin
ae (Siphonaptera: Ceratophyllidae), and other nest-dwelling insects we
re counted from the nests of the great tit, Pal-us major, and the pied
flycatcher, Ficedula hypoleuca, in southwestern Finland around a fact
ory complex emitting large quantities of sulphuric oxides and heavy me
tals. Protocalliphora azurea larvae were more frequently found in the
nests of P. major than in those of F. hypoleuca. The prevalence of P.
azurea larvae tended to be lower in polluted areas. The number of P. a
zurea larvae correlated positively with nest size and brood size of P.
major. This may be caused by difficulties in sanitation of large and
crowded nests. The numbers of fleas and their larvae were negatively a
ffected by moisture in the nests. Nests of F. hypoleuca contained more
adult fleas in polluted areas. This may indicate reduced resistance o
f birds exposed to heavy metals, but other possibilities are also disc
ussed. We found a detrimental effect of P. azurea larvae on the growth
of P. major nestlings, and an effect of fleas on mortality of F. hypo
leuca nestlings, but these effects were not enhanced by air pollution.
We conclude that the ectoparasites studied, at densities observed in
our study area, are of minor importance in determining the breeding su
ccess of these two bird species.