Female in-nest attendance predicts the number of ectoparasites in Darwin's finch species

Abstract

Selection should act on parental care and favour parental investment decisions that optimize the number of offspring produced. Such predictions have been robustly tested in predation risk contexts, but less is known about alternative functions of parental care under conditions of parasitism. The avian vampire fly ( Philornis downsi ) is a myasis-causing ectoparasite accidentally introduced to the Galápagos Islands, and one of the major mortality causes in Darwin's finch nests. With an 11-year dataset spanning 21 years, we examine the relationship between parental care behaviours and number of fly larvae and pupae in Darwin's finch nests. We do so across three host species ( Camarhynchus parvulus , C. pauper , Geospiza fuliginosa ) and one hybrid Camarhynchus group. Nests with longer female brooding duration (minutes per hour spent sitting on hatchlings to provide warmth) had fewer parasites, and this effect depended on male food delivery to chicks. Neither male age nor number of nest provisioning visits were directly associated with number of parasites. While the causal mechanisms remain unknown, we provide the first empirical study showing that female brooding duration is negatively related to the number of ectoparasites in nests. We predict selection for coordinated host male and female behaviour to reduce gaps in nest attendance, especially under conditions of novel and introduced ectoparasites.

Nesting Success and Nesting Height in the Critically Endangered Medium Tree Finch (Camarhynchus pauper)

“…Females brood the hatchlings during the first days after hatch and both parents provision the nestlings with ~3 food deliveries per hour. The chick feeding phase lasts ~12 days [45].…”

Age effects in Darwin’s finches: older males build more concealed nests in areas with more heterospecific singing neighbors

“…The female is a uniparental incubator and the incubation phase lasts 12–14 days (Kleindorfer 2007a , b ). Both parents provide food deliveries to nestlings until they fledge after 12–14 days (Kleindorfer et al 2021a ). Between 17 and 60% of highland Darwin’s finch nests are depredated across species and years (Kleindorfer 2007a , b ; Kleindorfer and Dudaniec 2009 ; O’Connor et al 2010 ; Cimadom et al 2014 ; Kleindorfer et al 2021b ).…”

Functional traits and foraging behaviour: Avian vampire fly larvae change the beak and fitness of their Darwin's finch hosts

“…Avian vampire fly larvae have been found in all Darwin's finch nests with nestlings in the Floreana Island highlands since 2004 (100% prevalence; Common et al, 2019, 2020; Kleindorfer et al, 2021; Kleindorfer & Dudaniec, 2016; Kleindorfer, Peters, et al, 2014). Highland nests had four times more avian vampire fly larvae per nest than lowland nests, which we measured in G. fuliginosa (O'Connor, Dudaniec, & Kleindorfer, 2010).…”