How will sea-level rise affect threats to nesting success for Seaside Sparrows?

Authored by Elizabeth A Hunter

Date Published: 2017

DOI: 10.1650/condor-17-11.1

Sponsors: United States Geological Survey (USGS)

Platforms: NetLogo

Model Documentation: ODD Mathematical description

Model Code URLs: https://doi.org/10.1650/CONDOR-17-11.1.s1

Abstract

Sea-level rise (SLR) threatens the nesting success of salt marsh breeding birds, including Seaside Sparrows (Ammodramus maritimus), by increasing the magnitude and frequency of extreme high tides that flood nests. However, the threat to nesting success from tidal flooding is intertwined with that of predation because the threats are connected through a trade-off along a nest height gradient. Therefore, to understand the risk to nesting success from SLR, it is necessary to consider predation threats simultaneously. I used an individual-based model of Seaside Sparrow nesting behavior, calibrated using empirical data on nest success rates and nest-site selection behaviors, to project the effects of SLR conditions on the relative importance of predation and flooding threats in affecting nesting success, and to investigate whether nest-site selection along a gradient of nest height can modulate the risk of SLR. Outputs from the model revealed that present-day levels of predation risk pose as great a risk to nesting success as tidal flooding under simulated SLR conditions with extreme flooding risks. Nest success rates could become very low under extreme SLR scenarios, especially when predation risk is very high. The risks of failure from either threat are linked through nest-site selection behaviors: In high-predation-risk seasons, failure probability from flooding is greater than it would be under lower predation risk, due to the predation avoidance behavior of nesting closer to the ground. Therefore, management actions to reduce the risk of excessive failures from predation could reduce the risk of failures from both threats-a potentially useful management strategy, given that controlling predation is more tractable than controlling increased flooding from SLR at a local level.

Tags

Predation individual based model habitat site selection Climate-change Sea-level rise Life-history Trade-offs Population viability Salt-marsh Nest success Ammodramus maritimus Seaside sparrow Breeding ecology Prescribed fire