Abstract
Understanding the relationships between nesting habitat quality and predation risk is essential for developing appropriate conservation management for threatened species. This is particularly relevant where anthropogenic pressures could decouple the environmental cues used by birds to assess nesting habitat quality from increased predation risk. In this study, we conducted a series of surveys and nest experiments to examine the nest predation rates of Reed Parrotbill (Paradoxornis heudei) a passerine bird between inland and tidal reed‐bed wetland habitats, at Yellow River Delta National Nature Reserve, Eastern China during 2008, and 2010–2012. We found significant differences in the habitat structural characteristics between the two adjacent wetland habitats that are critical for Reed Parrotbill nest‐site selection. Experimental trials using recently constructed and abandoned Reed Parrotbill nests as ‘artificial nests, quail eggs and predator‐exclusion measures, revealed that tidal mudflat crab (Helice tientsinensis) was the primary cause of Reed Parrotbill egg predation in tidal reed‐bed habitat. Annual predation rates of real nests from inland reed‐bed habitat varied from 35% to 68%, and predation rates of artificial nests were much lower than those from real nests. Pitfall sampling revealed that the abundance of tidal mudflat crabs was significantly higher in tidal reed‐bed habitat. Our data suggested that Reed Parrotbills breeding in tidal reed‐bed habitats may be highly vulnerable due to extremely high rates of nest predation (up to 100%), caused primarily by the high density of tidal mudflat crabs. The incongruence between nest‐site habitat preference and nest survival indicated an ecological trap scenario, which requires further studies on its proximate and ultimate causes as well as the development of effective conservation management for the Reed Parrotbill.
Highlights
The theory of habitat selection predicts that birds should prefer habitats that maximize their fitness during nest-site selection (Cody 1985)
We carried out a series of novel trials using recently constructed but abandoned Reed Parrotbill nests as ‘artificial nests’ containing quail eggs, and predator-exclusion measures to show that tidal mudflat crab is the primary cause of Reed Parrotbill egg predation in tidal reed-bed habitat and how this habitat may represent an ecological trap for the species
Our studies have revealed significant differences in the structural habitat characteristics between the two adjacent wetland habitats that are critical environmental cues for Reed Parrotbill nest-site selection
Summary
The theory of habitat selection predicts that birds should prefer habitats that maximize their fitness during nest-site selection (Cody 1985). Components such as structural habitat characteristics to serve as cues for aspects of nest site selection (Jaenike and Holt 1991, Clark and Shutler 1999) including nest placement (Rodewald et al 2010), nesting substrate and architecture (Schmidt and Whelan 1999), level of anthropogenic disturbance (Que et al 2015), and for concealment against predation risk (Martin 1993). Several studies have found that songbirds select breeding habitat subject to elevated predation rates and reduced nest survival (Misenhelter and Rotenberry 2000, Robertson and Hutto 2006) Such ecological traps often arise because anthropogenic pressures have disrupted the nest predator behavior, predator distribution and predator community composition in ways that are not recognized by the birds selecting the nest sites (Shochat et al 2005, Latif et al 2011). We carried out a series of novel trials using recently constructed but abandoned Reed Parrotbill nests as ‘artificial nests’ containing quail eggs, and predator-exclusion measures to show that tidal mudflat crab is the primary cause of Reed Parrotbill egg predation in tidal reed-bed habitat and how this habitat may represent an ecological trap for the species
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