When presented with the challenge of identifying sparrows and other grassland birds in the field, especially in winter, even experienced birders refer to these skulking phantoms as LBJs (or "little brown jobs"). But because the populations of many of these species are showing declines, understanding their distributions and habitat needs is crucial for conservation planning.
Since 1999, research ecologist Dr. Janet Ruth of the U.S. Geological Survey, Fort Collins Science Center, has been studying semidesert and Plains grasslands in southeastern Arizona to learn more about the birds that rely on these habitats.
"Identification is particularly challenging in the winter when these birds are cryptically colored, are not singing, and typically respond to disturbances by hiding in the grass or running along the ground like little mice," she says. "However, after several years of conducting research on habitat use by wintering grassland birds, I can tell you that the effort is well worth the struggle."
As a group, endemic grassland birds have shown steeper, more consistent, and more widespread population declines than any other guild of North American bird species. Although in recent years research on the ecology of grassland birds has increased, very little has focused on grassland birds in the winter. Hence, the motivation for this study.
Over the three winters (January through March) of 1999–2001, Dr. Ruth worked on semidesert and Plains grassland sites in southeastern Arizona, including the National Audubon Society's Appleton-Whittell Research Ranch (hereafter Research Ranch) and sites managed by the Bureau of Land Management (BLM), U.S. Forest Service (USFS), U.S. Fish and Wildlife Service (USFWS), and private ranchers. Then, when the project seemed finished, on 29 April 2002 the Ryan wildfire swept through 38,000 acres of foothills and grasslands at the southern end of the Sonoita Valley in southeastern Arizona, including over 90 percent of the Research Ranch. This fire provided an unexpected opportunity to study the effects of wildfire on grasslands and grassland birds. Armed with pre-fire data from the first phase of the project, Dr. Ruth added a Phase II, involving three additional years of research during the winters of 2003–2005. For this phase, she used the same protocols to gather data on a burned site (the Research Ranch) and on one of her nearby unburned sites (the BLM's Las Cienegas National Conservation Area) in order to assess the responses of birds and vegetation to a wildfire.
Both phases of the study incorporated two different kinds of bird surveys in order to address the challenges of identifying wintering grassland birds. For species that are relatively easy to identify when they flush—such as meadowlarks (Sturnella species), Chestnut-collared Longspurs (Calcarius ornatus), Horned Larks (Eremophila alpestris), and Sprague's Pipits (Anthus spragueii)—flushing line transects were conducted. This involves marking a series of 1,000-m lines at each site and then having teams of three walk along the lines, with two members of the team sweeping back and forth to flush reluctant birds. Birds were identified to the species level (or groups of species if that's all that was possible).
For species that are very difficult to identify when they flush—such as Baird's Sparrow (Ammodramus bairdii), Grasshopper Sparrow (Ammodramus savannarum), and Savannah Sparrow (Passerculus sandwichensis)—a second method was used called "flush mist netting" (many called it "herding sparrows"). Developed by University of Arizona collaborator Caleb Gordon for his study of winter sparrow movement patterns, this method involves setting up hourglass-shaped plots of 7 hectares at each site, in which 100 m of mist nets were located at the narrow part of the hourglass. Dr. Ruth then employed groups of 15–30 volunteers to walk through the plots from both ends, flushing the birds into the nets. Birds were then identified, banded, and released.
To determine whether there are particular structures or types of plants that grassland birds prefer in their winter habitat, it was necessary to characterize the vegetative structure and composition of these sites. Extensive vegetation measurements were conducted on all plots, including measures of shrub density, grass height, vertical grass structure, frequency of occurrence for various plant species and species groups (e.g., exotic species, native species, forb species), and plant biomass. These vegetation data are used to answer research questions focused on understanding how wintering grassland birds use their habitat and how vegetation and birds respond to wildfire.
This research project is a great example of effective professional and citizen partnerships for science. In addition to conducting research on grasslands managed by the USFWS, BLM, and USFS, partnerships were established with the Audubon Appleton-Whittell Research Ranch and several private ranchers who granted permission for scientists and volunteers to work on their property. Financial and in-kind support over the years came from the USGS, BLM, and USFWS, and was a collaborative effort between Dr. Ruth and Caleb Gordon, then a graduate student at the University of Arizona. In addition, 15 field technicians were employed over the years, and literally hundreds of volunteers came out to help "herd sparrows."
"One of the most enjoyable parts of this project was working with a huge group of wonderful local volunteers who were willing to come out and tramp through the grasslands, sometimes under less-than-perfect conditions," Dr. Ruth recalls. "In some winters we were faced with cold, wet, and snowy weather, and I was grateful for their persistence."
The pool of volunteers included undergraduate and graduate students from the University of Arizona and other universities, local birders, human "snowbirds" who spend the winters in Arizona, school groups, and assorted others corralled to help. As to their value, Dr. Ruth is clear: "Without this great human resource, this project would not have succeeded." Public participation in the sparrow project provided a substantial educational benefit to the local community and increased public awareness of priority grassland bird species and their habitat needs.
Dr. Ruth continues to conduct grassland bird research in southeastern Arizona. From 2004 to 2013 she conducted field work to study the distribution, abundance, and breeding ecology of the Arizona Grasshopper Sparrow (Ammodramus savannarum ammolegus) in the same area, funded by Arizona Game and Fish Department, Arizona State Parks, and BLM. As part of this project she has conducted roadside surveys for singing males throughout southeastern Arizona and southwestern New Mexico grasslands. She also mapped the territories of males, captured and color-banded males, located and monitored nests to study productivity, and measured vegetation structure on territories and around nests. On occasion she has run into a former "sparrow herder" whose response has been, "Oh, look, it’s the sparrow lady!"
As Dr. Ruth works through analyses of the extensive data gathered during these projects, she plans to publish several additional scientific articles about the response of vegetation and birds to wildfire, and the natural history, breeding ecology, and nest survival of Arizona Grasshopper Sparrows. These results will provide valuable information to public and private land managers interested in conserving grassland birds and their habitats.