DEVELOPING A CONSERVATION STRATEGY
FOR GRASSLAND BIRDS AT
SARATOGA NATIONAL HISTORICAL PARK

Natural Resources Report NPS/NER/NRR—2005/004

Carol L. Trocki and Peter W.C. Paton
Department of Natural Resources Science
University of Rhode Island Kingston RI 02881

October 2005

U.S. Department of the Interior
National Park Service
Northeast Region
Boston, Massachusetts

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Introduction

Project Goal
The goal of this project was to create a synthetic decision support document detailing the present value of managed grassland habitats to obligate grassland bird species within the Battlefield Unit of Saratoga National Historical Park (SARA). This document integrates available plans, guidelines, and data from SARA with current grassland bird management recommendations from the literature.

Park Purpose & Resource Management Goals
The purpose of Saratoga National Historical Park is to preserve and protect sites associated with the battles, siege, and surrender of British forces at Saratoga, which were decisive events in the winning of American independence (SARA Draft General Management Plan, NPS 2003). Goals for resource management at SARA include protecting, preserving, and maintaining the landscapes significant to the 1777 battles, siege, and surrender, and managing the park’s natural resources within the context of a cultural park (SARA Draft General Management Plan, NPS 2003). The recently completed General Management Plan for SARA seeks to base decisions on the best available scientific information and to conserve grasslands in support of cultural landscapes, as well as critical habitat

Documented Grassland Bird Decline
Grassland bird populations are declining throughout North America at a dramatic rate (Vickery et al. 1999a). Analysis of the North American Breeding Bird Survey (BBS) indicates that of 28 species of grassland-dependent breeding birds detected throughout North America, 68% (19 species) show a significant negative trend from 1966-2003 (Sauer et al. 2004; Appendix D). In northeastern North America, of all bird groups, grassland and shrubland dependent birds are exhibiting the most pervasive and steady declines in abundance (Witham and Hunter 1992; Askins 1993, 2000), which has resulted in considerable interest among conservation biologists.

In BBS analyses of the Northeast Region (US Fish and Wildlife Region 5) from 1980 to 2003, ten obligate grassland species were detected (Sauer et al. 2004). Of these, Ring-necked Pheasant (Phasianus colchicus), Vesper Sparrow (Pooecetes gramineus), Grasshopper Sparrow (Ammodramus savannarum), Eastern Meadowlark (Sturnella magna), and Savannah Sparrow (Passerculus sandwichensis) all showed significant negative trends (Sauer et al. 2004). Henslow’s Sparrow (Ammodramus henslowi), Upland Sandpiper (Bartramia longicauda), Northern Harrier (Circus cyaneus), and Bobolink (Dolichonyx oryzivorus) all showed non-significant results at the regional level, but significant declines continentally (Sauer et al. 2004). Horned Lark (Eremophila alpestris) appears to be increasing regionally, but declining nationally during this same time period (Sauer et al. 2004).

Partners in Flight (PIF) lists three of the above species (Henslow’s Sparrow, Upland Sandpiper, and Bobolink) as conservation priorities in the Northern Ridge and Valley Physiographic Area 17, a region that includes SARA (Rosenburg and Robertson 2004). PIF’s ranking system (detailed in Carter et al. 2000) lists Henslow’s Sparrow as a continental conservation priority, both Upland Sandpiper and Grasshopper Sparrow as high regional priorities, and Bobolink as a US National Watchlist species (PIF Species Assessment by Rocky Mountain Bird Observatory 2002). Although the northeast region of the United States may not support a large percentage of North America’s obligate grassland nesting species overall, it may be critically important for species with a greater proportion of their breeding population in this region, such as Henslow’s Sparrow (>20.0%), Grasshopper Sparrow (4.0%), Bobolink (13.7%), and Eastern Meadowlark (5.4%) (Wells and Rosenburg 1999).

At least one obligate grassland subspecies is already extinct in the Northeast. The endemic Heath Hen (Tympanuchus cupido cupido) was extirpated from Martha's Vineyard, Massachusetts in 1932 due to habitat loss (Askins 2000). Without immediate conservation measures and active management of remaining grassland habitat, several other obligate grassland bird species may also be extirpated from the region (Wells and Rosenberg 1999).

Among obligate extant grassland species in decline throughout North America, Henslow's Sparrow had the greatest rate of decline, estimated at 8.8% annually from 1966-1996 (Peterjohn and Sauer 1999). The rate of decline in Henslow’s Sparrow populations has increased from 6.0% annually during 1966-1979 to 10.4% annually from 1980-1996. A recent summary of population trends suggests that regionally, Henslow’s Sparrows are declining at 12% annually (Appendix D), resulting in a 50% decline in just a 6-year period (Sauer et al. 2004). Henslow's Sparrow has a limited breeding distribution range restricted to the northeastern and north-central United States (Herkert et al. 2002), with SARA at its eastern extent.

Current hypotheses suggest that grassland birds have declined throughout North America due to farmland abandonment and declines in hayfield acreage (Vickery and Dunwiddie 1997; Askins 1999, 2000), intensification of agricultural practices such as increases in mowing rotations of hay fields (Norment et al. 1999), habitat loss (Young and Osborn 1990), habitat fragmentation (Vickery et al. 1995), mortality from toxicants (Stone 1979), increases in nest parasitism from Brown-headed Cowbirds (Molothrus ater) (Zimmerman 1988), and adverse weather (Sauer et al. 1996). Habitat conversion and intensification of agricultural practices are probably the two primary causes of grassland bird declines in the
Northeast region. Since the early 1900s, reforestation of agricultural landscapes in New England has resulted in a substantial decline in the acreage of grasslands available to obligate grassland species (Askins 2000).

Although there is some controversy over whether extensive native grasslands existed prior to European colonization of the Northeast, available evidence suggests that some large coastal sandplain grasslands and heathlands occurred in the region (Askins 1999). Mehrhoff (1997) provided evidence of prairie or large tracts of grasslands historically occurring in New England, and although extensive grasslands most likely never existed here, there are some notable exceptions such as Hempstead Plains on Long Island. However, there are currently few self-sustaining grasslands in the region. Askins (2000) emphasized that in eastern North America, obligate grassland bird species are generally restricted to open habitats artificially maintained by human intervention. Conservation efforts must focus on maintaining and properly managing these habitats to prevent regional extinctions of grassland specialists.

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The body of the Report

pdf file 2
Appendices A and B

pdf file 3
Appendix C through Table 3, Grassland Generalists

pdf file 4
Appendix C continued through Protocol IIIa

pdf file 5
Appendix C continued through Appendix D

pdf file 6
Appendix E