Secretive marsh bird response to prescribed fire in Mid-Atlantic tidal marshes

Date
2010
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University of Delaware
Abstract
In North American tidal marshes, prescribed burning has been employed to manage waterfowl, furbearers, invasive plants, and fuels since at least the 1930’s. Prescribed burning may also affect non-target species, such as marsh birds, but few studies have examined these potential impacts, particularly in the mid-Atlantic region. To address this informational need, I studied breeding secretive marsh birds on the Chesapeake Bay in Dorchester County, Maryland, where prescribed marsh burning has been conducted for at least 70 years. I examined the effect of time since fire on density, nest success, productivity and occupancy. Seaside Sparrows (Ammodramus maritimus maritimus) were the most abundant species in the study area. Seaside Sparrow density was greatest on 2 - 4 months post-fire marshes, and densities decreased as time since fire increased. Seaside Sparrow nest survival rates were lowest on 5 or more years post-fire marshes, and highest on 3 - 4 years post-fire marshes. Nest survival was also dependent on landscape context and annual weather variation. Least Bittern (Ixobrychus exilis) and Virginia Rail (Rallus limicola) occupancy was positively influenced by fire. Saltmarsh Sparrows (Ammodramus caudacutus) appear to have a delayed response to winter prescribed burns, as occupancy was negatively impacted by burning over the short-term (3 years), but positively impacted over the long-term (24 years). Coastal Plain Swamp Sparrows (Melospiza georgiana nigrescens) occupied only ecotonal habitat, and did not respond strongly to prescribed burns. I found that prescribed marsh burning had a positive effect on Least Bittern, Virginia Rail, and Saltmarsh Sparrow occupancy, and that Seaside Sparrows were abundant in burned areas. However, there was some evidence that predation may increase immediately following a burn, which may have negatively impacted Seaside Sparrow nest success and productivity on marshes burned 2 - 4 months ago. The natural fire frequency of the study area has been estimated to be 4 - 6 years, indicating that marsh birds may have adapted to occasional fire events. For these reasons, I recommend burning once every 3 - 4 years to maintain habitat quality for breeding secretive marsh birds.
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