Temporal variation in the consequences of an exotic shrub on avian nest predation

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Date

2006-12

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The Ohio State University

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Abstract

Exotic plants are recognized as serious threats to biodiversity due to their tendency to disrupt ecosystem processes and alter floristic composition. Recent work also shows exotic plants can influence predator-prey interactions. For example, birds nesting in exotic shrubs such as Lonicera maackii (Amur honeysuckle) and Rosa multiflora (multiflora rose) in urbanized areas are more likely to have their nests depredated than if they nested in native substrates. However, no studies have evaluated whether or not this increased vulnerability to predation varies temporally over the course of a breeding season. Increased predation is especially likely early in the season given that certain exotics, such as Lonicera, show advanced leaf phenology and exhibit full leaf flush long before most other nesting substrates are available to breeding birds. This study tested if the risk associated with nesting in native substrates and two common exotic shrubs varied temporally across the breeding season for a common abundant understory nesting bird, the Northern Cardinal (Cardinalis cardinalis). Logistic exposure models were used to estimate daily nest survival rates of 607 cardinal nests found in riparian forests in central Ohio in 2001-2005. An information-theoretic approach was used to evaluate 4 a priori models explaining variation in daily nest survival. Results indicate that julian date and substrate type (native, Lonicera or Rosa) interacted to influence nest survival. Daily survival rates increased throughout the breeding season for nests in native substrates and Lonicera, whereas daily survival of nests located in Rosa remained more stable throughout the season. Although nests in Rosa were generally more vulnerable to predation than nests in Lonicera, season influenced relative vulnerability. Nests in Lonicera in early spring, prior to leaf emergence of co-dominant plants, showed the lowest rates of daily nest survival of all substrates. Understanding temporal variation in risk to nest predation may elucidate the mechanisms that determine effects of exotic plants on breeding birds. Advisor: Amanda D. Rodewald

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1st Place at the 3rd Annual CFAES Undergraduate Research Forum in the Environmental Category

Keywords

nest predation, exotic shrubs, phenology, temporal variation, Northern Cardinal, honeysuckle

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