Changes in Philornis infestation behavior threaten Darwin’s finch survival

Abstract

The conservation behavior framework is useful to identify key linkages between behavior and conservation practice. We apply this framework to a novel host-parasite system on the Galapagos Islands and ask if there have been changes in parasite oviposition behavior and host mortality patterns across the first decade (2004-2013) of its known association. The Dipteran parasite Philornis downsi was first discovered in Darwin’s finch nests in 1997 and is the biggest threat to the survival of Galapagos land birds. Host mortality has increased over the past decade. In Dipterans, pupation and pupae size are determined by access to host resources. Here, we test the hypothesis that P. downsi flies are laying eggs in finch nests earlier in the nestling phase to maximize larval feeding time and therefore chance of pupation success before host death. The results show fewer 1st instar larvae later in the host nesting cycle in support of earlier egg laying behavior by female flies. Between 2004 and 2013, parasite intensity increased from ~28 to ~48 parasites per nest, host mortality increased from ~50% to ~90%, and host age at death decreased from ~11 to ~5 days. The earlier age at host death was correlated with fewer pupae (from ~50% to ~20%) and smaller pupae size (~10% decrease). Changes in parasite behavior reveal new fitness costs to both the parasite and Darwin’s finches. These findings underscore the need for urgent conservation action to save Darwin’s finches from extinction due to a novel, lethal and introduced parasite [Current Zoology 60 (4): 542–550, 2014].

Divergent foraging behavior in a hybrid zone: Darwin’s tree finches (Camarhynchus spp.) on Floreana Island

“…In-nest chick mortality was caused by flesheating larvae of the introduced parasitic fly Philornis downsi (Kleindorfer et al, , 2014bO'Connor et al, 2010b;Dudaniec et al, 2010). Medium tree finch nests had more P. downsi larvae compared with most other Darwin's finch species (Dudaniec et al, 2007;Kleindorfer et al, 2014b). Although higher body condition is often linked with fewer parasites or higher survival under conditions of parasitism (Brown et al, 2000;Møller et al, 1998), this does not directly apply here because the parasite P. downsi consumes the blood of nestling birds and not adults Fessl et al, 2006;Huber, 2008;O'Connor et al, 2014).…”

“…This finding seems counter-intuitive. Nesting success has been very low in medium tree finch, with 0% fledging success since 2012 (Kleindorfer et al, 2014b). In-nest chick mortality was caused by flesheating larvae of the introduced parasitic fly Philornis downsi (Kleindorfer et al, , 2014bO'Connor et al, 2010b;Dudaniec et al, 2010).…”

“…Nesting success has been very low in medium tree finch, with 0% fledging success since 2012 (Kleindorfer et al, 2014b). In-nest chick mortality was caused by flesheating larvae of the introduced parasitic fly Philornis downsi (Kleindorfer et al, , 2014bO'Connor et al, 2010b;Dudaniec et al, 2010). Medium tree finch nests had more P. downsi larvae compared with most other Darwin's finch species (Dudaniec et al, 2007;Kleindorfer et al, 2014b).…”

Animal behavior can inform conservation policy, we just need to get on with the job – or can it?

“…Berger-Tal and Saltz (2014) discuss how GPS technology serves as an aid to managers post reintroduction of animals, and provide data from fallow deer and from oryx to support their argument. An additional four papers are original research papers that explore the relationship between animal behavior and its implications for conservation in fish (Paciorek et al, 2014), birds (Blesdoe and Blumstein, 2014;Kleindorfer et al, 2014) and, on a larger scale, elephants (English et al, 2014). Caro and Riggio (2014) review six species (and associated subspecies) of African 'trophy' mammals: ele-phants, black and white rhinoceros, lions, leopards, and buffalo.…”

“…This promising result leads the authors to suggest that, while this work is still in its infancy, captive-raised fish may be used as a source of animals for reintroduction purposes in restored habitat. Kleindorfer et al (2014) take advantage of the 'natural laboratory' provided by isolated islands to explore the effect of recently introduced parasites on naïve birds in the Galapagos. Their data depict a rather bleak picture of three species of Darwin's finches rapidly succumbing to a novel parasite fly larvae.…”