Birds of Early Successional Habitats in the Delaware Water Gap National Recreation Area; Distribution, Abundance, and Management

Master, Terry; Sheehan, Jim; George, Gregory; Swatzentruber, Beth; Hawk, Steven

A two-year survey of the early successional habitat avian community was conducted during the breeding seasons of 2002 and 2003 in the Delaware Water Gap National Recreation Area. Bird species richness, diversity, density, detection rates, and occurrence were determined and compared between years, among fields, and with vegetative parameters to elucidate the distribution and abundance of birds characteristic of open field habitats within the park. This information was used to develop management suggestions regarding the enhancement of habitat for these species. The explicit purpose of this project was to inventory grassland birds within the Delaware Water Gap National Recreation Area. Variable circular plot point counts were used to determine distribution and abundance patterns of early successional bird species, in general, and species occurrence, detection rates, species richness, diversity, and density, in particular, in open field habitat (<15% shrub cover) of the Delaware Water Gap National Recreation Area. All open fields (32) ranging in size from 4–36 ha (10–89 ac) were surveyed and comparisons made between years and among survey sites in order to characterize the early successional bird community. A listing of the ten species with the highest values for any of the above mentioned parameters is composed of a slight majority of shrubland species, including common yellowthroat and song sparrow, compared to typical grassland species. This may have occurred because of detections from the often shrubby perimeter of relatively small fields which compose most of the open habitat within the park. Thus, shrubland birds play a larger role than expected in project results even though predominantly shrubby fields were expressly eliminated from the sampling regime. Grassland species richness, diversity, and density values were generally higher in larger fields and those with relatively sparse vegetation where grass dominated. Shrubland species did not exhibit evidence of area sensitivity. Association with shrubs was not specifically investigated since most shrubby habitat existed around field borders well away from vegetation sampling transects. Suggested management options focus on a community-based approach for grassland birds, with a predominantly species-level approach for shrubland birds, paying attention to sensitivities (e.g., area requirements, vegetation composition, landscape habitat patterns) and implementation within a management decision hierarchy.

Birds of Early Successional Habitats in the Delaware Water Gap National Recreation Area; Distribution, Abundance, and Management

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