Sex interacts with age-dependent change in the abundance of lice-infesting Amur Falcons (Falco amurensis)

Andrea Harnos,Zoltán Vas,Nóra Vili,R. Suresh Kumar,Imre Sándor Piross,Péter Palatitz,Lajos Rózsa,Manju Siliwal,Nóra Magonyi,Péter Borbáth,Péter Fehérvári,Szabolcs Solt

doi:10.1007/s00436-020-06753-w

Abstract

Sex-biassed and age-biassed parasite infections are common in nature, including ectoparasites-vertebrate host systems. We investigated the effect of Amur Falcons’ sex, age and body size on the abundance of their lice at a migratory stopover site, where the falcons’ habitat use and behaviour are more homogeneous across sex and age categories than during the breeding season. We sampled Amur Falcons in Nagaland, India at major roosting sites in 2016. We applied generalized linear models (with negative binomial distribution and log-link) to model the abundance of their two most numerous lice (Colpocephalum subzerafae and Degeeriella rufa) using the host age category (juvenile or adult) and wing length, both in interaction with sex, as explanatory variables. The abundance of C. subzerafae was only affected by host age, being nearly four times higher on juveniles than on adults. Juveniles were also more infested with D. rufa than the adults. Additionally, the abundance of the latter species was lower on adult male Falcons as compared to adult females. A juvenile bias in ectoparasite infestations is common in nature, probably due to juveniles being immunologically naïve, more resource-limited and may be inexperienced in body maintenance behaviours like preening and grooming. On the other hand, female-biassed infestations are much rarer than male-biassed infestations. We briefly discuss the possible causes of female-biassed infestations on Amur Falcons reported here, and in the closely related Red-footed Falcon and Lesser Kestrel as reported in the literature.

Highlights

Though avian ectoparasites rarely have detrimental effects on their hosts, levels of their infestations still covaries with host health status for two reasons
We found three louse species on the Amur Falcons, all of which have been described from this host previously (Price et al 2003; Piross et al 2015)
Our models indicated that only age exerted a significant effect (p = 0.0006) on the mean abundance of C. subzerafae

Summary

Introduction

Though avian ectoparasites rarely have detrimental effects on their hosts, levels of their infestations still covaries with host health status for two reasons. High parasite burdens could constitute both a cause and a consequence of poor health status in birds (Clayton et al 2015). This is true for large-bodied bird species like raptors because they tend to host relatively high ectoparasite burdens (Rózsa 1997). The importance of monitoring the health status of their populations, as judged from levels of parasite infestations, is increasingly important for conservation purposes (Órdenes et al 2005; Liébana et al 2011; Saxena 2017; Tinajero et al 2019; Yosef et al 2019). Host age, sex and body size likely affects individual infestation levels, and the seasonality of infestation dynamics must be taken into account (Lamb and Galloway 2016; Yunik et al 2016)

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