Suboptimal conditions lead to differences in habitat use and nest survival of imperiled tidal marsh sparrows between an urban marsh and nearby non-urban island
Sea level rise and human development are threatening the extinction of some saltmarsh birds. Nests risk failure because of flooding when built low to the ground, but taller nests face increased predation risk. To better understand how habitat characteristics and urbanization influence reproductive s...
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| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Resilience Alliance
2024-12-01
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| Series: | Avian Conservation and Ecology |
| Subjects: | |
| Online Access: | https://www.ace-eco.org/vol19/iss2/art15 |
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| Summary: | Sea level rise and human development are threatening the extinction of some saltmarsh birds. Nests risk failure because of flooding when built low to the ground, but taller nests face increased predation risk. To better understand how habitat characteristics and urbanization influence reproductive success in saltmarsh ecosystems, we modeled factors discriminating nest sites from unused available sites and nest survival of a high-marsh specialist, Saltmarsh Sparrow ( Ammospiza caudacuta ), and a low-marsh specialist, Seaside Sparrow ( A. maritima ), at three sites representing different degrees of surrounding urbanization and degradation in New York, 2018–2019. The two most urban sites contained mammalian predators, and the non-urbanized island contained a colony of gulls that are potential predators. Sparrow nest site use depended positively on cover by the tall grass Spartina alterniflora . At the most degraded urban site, this relationship was strongest at high elevation, and at the island site it was strongest near the gull colony. Nest survival of both species was positively related to average vegetation height around nests, and negatively related to daily tide height. At the island site, nest survival was unrelated to proximity to the gull colony. Nests were highest off the ground at the most urbanized site, which experienced the highest tides, but nest survival was still low in one year. The effect of nest height on survival was not always positive and depended on tide height, nest stage, and sparrow species. Predation risk may explain why at higher elevations, sparrows placed nests in taller vegetation. At the island site, nest survival was high even within an active predator colony, but at the most urbanized site Saltmarsh Sparrows appeared unable to mitigate factors threatening nest survival. Restoration designs that include tall vegetation at high elevation may help tidal marsh sparrows to find a tradeoff between flooding and predation risk. |
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| ISSN: | 1712-6568 |