Nesting Potential for High Marsh Nesting Birds in Tidal Marshes of Virginia
Tidal marshes are one of the most characteristic habitats of estuaries in the Chesapeake Bay and Mid-Atlantic Region. A number of bird species that are entirely dependent on high marsh zones of tidal marshes for nesting are of conservation concern because of recent population declines. The Black Rail is the most imperiled bird species among this group. Recent evidence suggests that Black Rails may be heading towards extirpation in the Mid-Atlantic region. High marsh nesting bird species are particularly vulnerable to changes in sea level and nest predation. Determining the relative contribution of the leading factors believed to be influencing population declines requires special investigation to aid management efforts. This study was designed to investigate the nesting potential of marsh birds using high marsh habitats in Virginia. Birds that nest in the high marsh may be highly susceptible to nest depredation because of low water levels that make for easy accessibility by mammalian and other nest predators. We determined the nest fate of natural bird nests and by using an artificial nest experiment. The number of natural bird nests discovered during the study was low and lacked the sample size for adequate statistical summary. However, the fate of artificial nests monitored over 11 experimental plots showed relatively high nest predation rates. Daily nest survival of artificial nests was 0.88 and an overall probability of nest success of 0.07 across 99 nests. The average number of exposure days before an artificial nest was depredated was less than half the period required for successful incubation by most marsh nesting species including the Clapper Rail, Virginia Rail, and Black Rail. Daily survival rates and nest success of artificial nests were somewhat lower compared to natural nests from other studies of marsh nesting birds. Although some caution must be made when comparing artificial and natural nest outcomes, the results suggest that birds nesting in high marsh are vulnerable to high rates of nest depredation.