Impact of botfly (Philornis pici) parasitism on growth and survival House Wren (Troglodytes aedon) nestlings

QUIROGA, M.; REBOREDA, J.

JOURNAL OF FIELD ORNITHOLOGY

Wiley-Blackwell

Lugar: Richmond; Año: 2008

0273-8570

Abstract. Flies of the genus Philornis (botflies) have larvae that live subcutaneously on altricial nestlings. Some studies have shown that these larvae have sub-lethal or lethal effects on their hosts, while others found no evidence of detrimental effects. We used a large set of observational data to study the impact of botfly (P. pici) parasitism on growth and survival of House Wren (Troglodytes aedon) nestlings. We analyzed if: 1) differences in intensity and latency of botfly parasitism among broods, and 2) differences in intensity of parasitism and hatching order within broods, were associated with probability of nestling survival. Prevalence of botfly parasitism was 25% (n = 157 broods), while mean intensity and latency of parasitism were 12.8 larvae per nestling and 3.9 days, respectively. Nestling survival in infested broods was 42% of the one in non-infested broods. Among infested broods, the proportion of nestlings that survived was negatively associated with intensity of parasitism, and positively associated with age of the brood at the time it was parasitized. Within infested broods, there was no association between intensity of parasitism and nestling survival, but first hatched nestlings had a higher probability of survival than last hatched nestlings. Infested nestlings that survived had lower growth rates of head plus bill length, wing length, and body mass, than nestlings in non-infested broods. Our results indicate that P. pici have lethal and sub-lethal effects on House Wren nestlings and that intensity of parasitism and age of nestlings at the time they are infested are two important factors that influence nestling survival.