Henslow's Sparrow in the Midwest


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This web site provides monitoring and research information on Henslow's Sparrow (Ammodramus henslowii) in the midwestern United States. Henslow's Sparrow is a U.S. Fish and Wildlife Service (FWS) Species of Concern and is a high-priority nongame species. Support for this effort comes from the Biological Resources Division (BRD) of the U.S. Geological Survey and the FWS.  Several products from Rolf Koford's contribution to monitoring and research are available. An account of the species in Iowa was published in Iowa Bird Life. Also available are maps of sites in Iowa where we detected Henslow's Sparrows in 1996-7 and sites in Missouri where the species has been detected by other investigators and the Missouri Breeding Bird Atlas. The maps of the Iowa distribution were created in ArcView; the files and metadata are available from Dr. Koford.  The species has been seen regularly at O.L. Kipp State Park (SE Minnesota) in recent years.

One important issue is whether to list this species as Threatened under the Endangered Species Act. The FWS made the decision not to list the species for now but to keep it as a Species of Concern.

Another important issue is the lack of adequate survey data. This species is not well surveyed by the North American Breeding Bird Survey because the species is rare across most of its range. Since 1996, I have been working on issues needed to develop a better survey for Henslow's Sparrows

A recent status assessment (Pruitt 1996:78) included the following research and monitoring needs:

"... identify additional persistent populations in areas of suitable habitat" to add to the list of known sites, thus facilitating monitoring "the status of the largest, persistent populations."

"A database of all known or suspected breeding sites, and any research or monitoring efforts associated with these sites, should be established and maintained."

"... evaluate the feasibility of modifying or amending existing surveys to improve the potential to detect Henslow's Sparrow."

Henslow's Sparrows nest in idle or lightly-grazed tall-grass prairie and can be locally abundant in such habitat. The decline of this species may be tied to its shrinking habitat base in the prairie ecosystem. The species does not require natural prairie for nesting, however, and also nest in fields of planted grasses that have suitable stature and size. Henslow's Sparrows nest in large (usually >50 ha), grassy fields that have moderate amounts of forbs and little woody vegetation. This preferred habitat, including tall-grass-prairie remnants and planted grasslands of similar structure, will become increasingly rare as old-fields in the northeastern U.S. succeed to forests, as increases in the price of corn and soybeans promote cultivation of marginal land, and as the Conservation Reserve Program (CRP) shifts to smaller, more linear, protected areas. Biological reserves, managed by the FWS and other agencies and organizations, will be increasingly important for the species' survival.

Managers of biological reserves will need to know which fields should be managed for breeding Henslow's Sparrows to sustain the meta-population. A field's attractiveness to Henslow's Sparrows may be affected not only by its size, but also by distance from other suitable fields (or other nesting conspecifics) and the composition of the landscape matrix. The effects of these factors probably interact and all may vary across space and time. Currently, very little is known about these relationships.

The first step toward analyzing these relationships is mapping the current distribution in a region. My field assistants and I have been mapping sites in southern Iowa and parts of Ohio. Areas of the target states with relatively large amounts of grassy cover (hayland, pastureland) were identified. Known concentrations of Henslow's Sparrows were also identified (Pruitt 1966). In these identified areas, roadside surveys were conducted along secondary roads. Field assistants drove along pre-determined routes, stopping every quarter-mile in appropriate habitat (grassy cover on at least one side of the road). Point counts were conducted from the side of the road. Field work, with two assistants, was conducted from mid-May through mid-August.

Literature Cited:Pruitt, L. 1996. Henslow's Sparrow status assessment. U.S. Fish and Wildlife Service, Northcentral Region, Fort Snelling, Minnesota. 113 pp. A summary is available.

Rolf Koford

Phone: (515) 294-3057

Rolf Koford's research page

Rolf Koford's home page

URL: http://www.public.iastate.edu/~hesp/homepage.html

Updated 14 July, 2000