Seasonal fecundity and costs to λ are more strongly affected by direct than indirect predation effects across species

Ecology
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Abstract

Increased perceived predation risk can cause behavioral and physiological responses to reduce direct predation mortality, but these responses can also cause demographic costs through reduced reproductive output. Such indirect costs of predation risk have received increased attention in recent years, but the relative importance of direct vs. indirect predation costs to population growth (λ) across species remains unclear. We measured direct nest predation rates as well as indirect benefits (i.e., reduced predation rates) and costs (i.e., decreased reproductive output) arising from parental responses to perceived offspring predation risk for 10 songbird species breeding along natural gradients in nest predation risk. We show that reductions in seasonal fecundity from behavioral responses to perceived predation risk represent significant demographic costs for six of the 10 species. However, demographic costs from these indirect predation effects on seasonal fecundity comprised only 12% of cumulative predation costs averaged across species. In contrast, costs from direct predation mortality comprised 88% of cumulative predation costs averaged across species. Demographic costs from direct offspring predation were relatively more important for species with higher within-season residual-reproductive value (i.e., multiple-brooded species) than for species with lower residual-reproductive value (i.e., single-brooded species). Costs from indirect predation effects were significant across single- but not multiple-brooded species. Ultimately, demographic costs from behavioral responses to offspring predation risk differed among species as a function of their life-history strategies. Yet direct predation mortality generally wielded a stronger influence than indirect effects on seasonal fecundity and projected λ across species.

Publication type Article
Publication Subtype Journal Article
Title Seasonal fecundity and costs to λ are more strongly affected by direct than indirect predation effects across species
Series title Ecology
DOI 10.1002/ecy.1860
Volume 98
Issue 7
Year Published 2017
Language English
Publisher Ecological Society of America
Contributing office(s) Coop Res Unit Seattle
Description 10 p.
First page 1829
Last page 1838
Country United States
State Montana
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