Philornis ectoparasitism of Pearly-eyed Thrashers. I. Impact on growth and development of nestlings

Abstract

Growth rates varied little among unparasitized (normally developing) Pearly eyed Thrasher nestlings. Botfiy ectoparasitism, however, significantly retarded growth and development in parasitized young. Parasitized nestlings showed different growth patterns at various ages, depending on the timing of the initial parasitic attack and the extent of larval infestation. Nestling growth was most affected within the first 1.5 weeks after hatching, the period of maximum growth rate in 4 of 5 sampled growth characters (body mass, culmen, ulna, tarsus). The ninth primary feather showed accelerated growth as fiedging approached. Body mass and tarsus were most affected by ectoparasitism. Nestling body mass fluctuated markedly in response to the biomass of the infesting larvae. Tarsus length was retarded in parasitized young throughout the nestling period. A combination of inherent and environmental factors showed the need to consider morphological characters in addition to body mass as possible determinants of avian growth.

Citation

Arendt, Wayne J. 1985. Philornis ectoparasitism of Pearly-eyed Thrashers. I. Impact on growth and development of nestlings. Auk 102:270–280.