Explaining variation in brood parasitism rates between potential host species with similar habitat requirements

Abstract

Host specialization evolved in many parasite-host systems. Evolution and maintenance of host specificity may be influenced by host life-history traits, active host selection by the parasite, and host anti-parasite strategies. The relative importance of these factors is poorly understood in situations that offer parasites a choice between hosts with similar habitat requirements. The common cuckoo Cuculus canorus is a generalist parasite on the species level, but individual females prefer particular host species. In reed beds of the Yellow River delta, China, two potential hosts with similar nest characteristics, Oriental reed warblers Acrocephalus orientalis and reed parrotbills Paradoxornis heudei, breed in sympatry. We found that warblers were parasitized at much higher rates than parrotbills. Both hosts recognized and rejected non-mimetic model eggs well, indicating that they have been involved in an arms-race with cuckoos. Cuckoo eggs closely resembled warbler eggs, and such eggs were mostly accepted by warblers but rejected by parrotbills. Only warblers recognized adult cuckoos as a specific threat. Both hosts were equally good at raising cuckoo chicks. Low nest density, partial isolation by breeding time, small scale differences in nest and nest site characteristics, and high rejection rates of natural cuckoo eggs are likely responsible for the low current parasitism rate in parrotbills. This study emphasizes the importance of integrating the study of general host life-history characteristics and specific antiparasitism strategies of hosts across all breeding stages to understand the evolution of host specificity. Response to Reviewers:Please see attached file as "Reply to comments (EVEC-D-15-00179)_R1".

Egg-spot matching in common cuckoo parasitism of the oriental reed warbler: effects of host nest availability and egg rejection

“…The Oriental Reed Warbler, which is similar to its sister, the Great Reed Warbler of Europe, displays relatively high egg discrimination towards cuckoo eggs (Lotem et al 1995;Moskát and Honza 2002;Li et al 2016). However, the cognitive signature (either from the background color or/and egg spot) involved in the recognition process is not clearly understood.…”

“…The Oriental Reed Warbler (Acrocephaus orientalis) is frequently parasitized by the Common Cuckoo in eastern China Yang et al 2014), where both species lay dark, brown-spotted eggs (Li et al 2016). We used egg spots as the main feature to investigate the phenomenon of egg matching between cuckoo and warbler and its effect on egg rejection conducted by the warbler.…”

Is brood parasitism related to host nestling diet and nutrition?

“…For fledging success analyses, the a priori temporal criterion for successful redstart fledging was that nestlings survived to 11 days of age (following Järvinen 1990). For cuckoos, the criterion was 18 days (Grim 2006c), with the day of hatching ¼ day 0 (Li et al 2016). We managed to follow all cuckoos and all but 1 redstart brood through to fledging; thus, we applied the temporal criterion to only 1 nest.…”

Russet Sparrows spot alien chicks from their nests

“…Although most studies have been done on coevolutionary interactions at the pre-laying or egg stages of the breeding cycle, hosts may also show defenses at the chick stage by deserting (Langmore et al 2003;Grim 2007) or evicting (Sato et al 2010;Yang et al 2015b) alien nestlings. However, without studying several, and ideally all, breeding stages (e.g., prelaying, egg, chick), it is hard to tell why some hosts escape parasitism or reduce its rate substantially (Briskie et al 1990;Grim et al 2011;Li et al 2016).…”