Parents respond in sex-specific and dynamic ways to nestling ectoparasites

Abstract

Nest ectoparasites can impose significant costs to altricial nestlings that are confined to the nest and dependent on parental care. These costs are often passed on to parents who may compensate for, or magnify, the direct costs of parasites on their nestlings through adjustments in parental care behaviour. If the effects of ectoparasites on nestlings vary across development, parents would be expected to dynamically adjust their behaviour across time with the possibility that males and females may vary in their responses. Currently, we lack a complete understanding of the potential sex differences and variation in parental care behaviour across the nestling period as a function of offspring parasite infection. Our experimental study compared disinfected and parasitized treatment groups to examine how northern fowl mites, Ornithonyssus sylviarum, in nests of the North American barn swallow, Hirundo rustica erythrogaster, affect parental care behaviour. Specifically, we addressed how provisioning rates and nest attendance behaviours (time spent at the nest) changed in response to ectoparasite infection early (day 7) and late (day 13) in the nestling period, and between male and female parents. Early in the nestling period, female provisioning rates were lower for parasitized nests than for disinfected nests whereas male provisioning rates did not differ between treatments. However, males of parasitized nests showed higher nest attendance whereas females did not alter their attendance of nestlings as a function of the parasite manipulation. Later in the nestling period, parental care behaviours changed dramatically. Male provisioning rates were higher for parasitized nests than for disinfected nests whereas female provisioning rates did not differ between treatments. Both males and females showed greater nest attendance for parasitized nests compared to disinfected nests on day 13. These findings suggest that parasites do affect provisioning and nest attendance behaviours: parental care responses differ between males and females, and are dynamic across the nestling developmental period.