Bird Observer - The New England Birding Journal

Bird Observer

The Birding Journal for New England

June 2015

Vol. 43, No. 3

The Buzz on Golden-winged Warblers in Vermont

Mark LaBarr


Male Golden-winged Warbler at a project site in Hinesburg, Vermont. (Phoyo by John Hannan.)

It all started with a power line right-of-way owned by the Vermont Electric Power Company (VELCO). This right-of-way provides a swath of early successional habitat that slices through the southern Champlain Valley of Vermont. In 2012, Audubon Vermont, as part of its Champlain Valley Bird Initiative, partnered with VELCO and University of Vermont graduate student Christine Peterson to better understand the use of the right-of-way by a suite of shrubland birds and to help guide management actions. The bird species of interest included Golden-winged, Blue-winged, and Prairie warblers, as well as Eastern Towhee, Field Sparrow, Brown Thrasher, and American Woodcock. The one thing these species had in common, or so we thought, was that their populations were all declining in Vermont. From the right-of-way surveys, the project grew to focus primarily on Golden-winged Warblers. We wanted to determine where these warblers were located in the valley and how Audubon Vermont could work with partners and landowners to maintain and enhance appropriate habitat.

Golden-winged Warblers have been declining across their range for many years due to loss of the early successional habitat in which they breed, changes in land use patterns, and hybridization with their cousins the Blue-winged Warbler. These declines have resulted in the petitioning for federal listing of this species and the creation of the Golden-winged Warbler Working Group. This group has developed a conservation plan including best management practices for the different habitat types this species favors. And there are many such habitats. From the young forests of the southern Appalachians, to the abandoned farmlands of New York and Vermont, to the aspen parklands of the upper Midwest, the Golden-winged Warbler uses a variety of early successional habitats for breeding

The Golden-winged Warbler Working Group has also created Focus Areas to prioritize locations for conservation actions to increase habitat and thus increase the overall population. The National Audubon Society has been working in Focus Areas in North Carolina, Pennsylvania, New York, Vermont, and Michigan. In Vermont, the VELCO right-of-way bisects one of these Focus Areas.

Before our recent studies began, the Golden-winged Warbler Working Group estimated that Vermont hosted approximately 20 pairs, and the recently completed second Vermont Breeding Bird Atlas showed a slight decline (-7%) from the first atlas with the highest concentrations of Golden-winged Warblers occurring in the Champlain Valley (Renfrew 2013). Audubon Vermont’s VELCO surveys conducted by Audubon staff and citizen scientists using a modified playback protocol, located a modest eight Golden-winged Warblers in 2012. That number, however, rose to 12 in 2014. Did this change suggest that Golden-winged Warbler populations were increasing in Vermont or was this variability the result of survey techniques or management actions?

To answer some of these questions, Audubon Vermont with support from the National Fish and Wildlife Foundation and the Southern Lake Champlain Fund decided to conduct a focused search for Golden-winged Warblers in the southern Champlain Valley in 2014. The southern Champlain Valley from Burlington to Rutland is part of the Golden-winged Warbler Working Group Great Lakes Focus Area 16. We figured that if we could find the birds, we could then work with landowners to maintain and enhance the ephemeral habitat that supports them. First we needed to locate suitable habitat. Fortunately, the interest of one of Vermont’s premier bird enthusiasts, Ted Murin, was piqued by the idea of locating this seemingly rare species. After scouring habitat images for the southern Champlain Valley, he located more than 130 sites that “looked good,” in other words contained a mixture of shrubs, herbaceous vegetation, and trees. Most of this habitat was abandoned farmland in the process of becoming reforested.

Our next challenge was to gain access to these sites. We sent letters to 150 landowners, public and private, requesting permission to survey their properties. Roughly 40 landowners, most of them private, allowed a small group of volunteers and Audubon staff to see what we could find. Some survey sites were impenetrable thickets of native and non-native shrubs and, in a couple of instances, took more than a day to survey. Others, including school grounds and town parks, were easily accessed by maintained trails. Surveys consisted of area searches often with playback of Golden- winged Warbler songs and calls, as well as distress calls of birds mobbing an owl. All sites were surveyed in the morning, but surveys sometimes extended into the afternoon when birds continued to be active.


Female Golden-winged Warbler with nesting material. (Photo by Curtis Smalling)

One of the difficulties we encountered was that just because a bird is singing a Golden-winged Warbler song does not mean it is a Golden-winged Warbler. On many occasions these birds would turn out to be Blue-winged Warblers or one of the hybrids, Brewster's or Lawrence's warbler. Due diligence was needed to confirm an actual Golden-winged Warbler, but sometimes even our best efforts left a question mark as to what species it was.

By the end of June 2014 most of the information was in. We had surveyed roughly 60 sites ranging in size from just a couple of acres to more than 40 acres. Sites included sections of the VELCO right-of-way, previously known locations, and a subset of the 130 potential sites our volunteer had identified. In all, we located 212 warblers, of which 35% were Golden-winged Warblers, 40% were Blue-winged Warblers, and 25% were hybrids or birds we could not positively identify.

Ted Murin’s predictions were impressively accurate, as more than 80% of the potential sites that he identified and we were able to survey had at least one of the warblers. Because we surveyed only a third of the predicted habitat areas, it seems likely that many more Golden-winged warblers are out there than previously known.


Golden-winged Warbler nest. (Photo by Curtis Smalling.)

The second and maybe more important part of the project was connecting with landowners to create, maintain, and enhance suitable habitat for Golden-winged Warblers and other shrubland obligates. Audubon Vermont is well situated to undertake this task as working directly with landowners is a key component of the Champlain Valley Bird Initiative. Since 2009, Audubon Vermont has been providing Champlain Valley landowners with habitat assessments focusing on shrubland and grassland birds. In addition, in 2013, Audubon Vermont partnered with the Natural Resources Conservation Service (NRCS) and the Vermont Fish and Wildlife Department to provide technical and financial assistance to encourage landowners to create habitat for Golden-winged Warblers through NRCS’s Environmental Quality Incentive Program. This assistance, combined with the management recommendations developed for VELCO, put Audubon Vermont and its partners in an ideal place to undertake this outreach effort.

So, with known locations of Golden-winged Warblers and ongoing funding, Audubon Vermont is continuing its work in the southern Champlain Valley. Audubon Vermont is already working with many new landowners including The Nature Conservancy, the Winooski Valley Park District, the State of Vermont, and several private individuals to develop management plans for their properties. In 2015, we plan on reaching out to additional landowners and partner organizations and continuing to survey areas of the Valley suspected of hosting Golden-winged Warblers. Our surveys of the VELCO right-of-way will be conducted for the fourth year in a row with a special focus on Golden-winged Warblers. VELCO is even developing an avian data collection component to their geographic information system (GIS) that is based on our surveys and will allow VELCO staff, trained by Audubon, to collect priority bird data.

Of course, we still have many questions as work on this population expands. How are current management practices affecting population size and reproductive success? Are the increasing numbers of Blue-winged Warblers impacting hybridization rates? Are Golden-winged Warblers present in the northern Champlain Valley at levels similar to the southern Champlain Valley? For now, we know that Golden-winged Warblers are present in Vermont in numbers not previously expected and that there is more to be learned about the nuances of this population and how it relates to other populations across its range.

Citations

  • Golden-winged Warbler Working Group. 2013. Best management practices for Golden-winged Warbler habitats in the Great Lakes region. Available online at: http://www.gwwa.org/ resources/GWWA-GLRegionalGuide_130808_lo-res.pdf. Accessed April 5, 2015.
  • Renfrew, R. B. 2013. The second atlas of breeding birds of Vermont. Lebanon, NH: University Press of New England.


Mark LaBarr is Conservation Biologist and Program Manager and oversees conservation projects, project staff, and volunteers for Audubon Vermont including the Champlain Valley Bird Initiative and the Endangered Species Recovery Project. As a biologist, his focus is on the Common Tern Recovery Project as well as efforts to better understand breeding populations of Golden-winged Warblers and other grassland and shrubland obligates in the Champlain Valley. He has a master bird banding permit and runs the Audubon bird banding station at the Green Mountain Audubon Center. He works in close cooperation with partner agencies and organizations such as the Vermont Fish and Wildlife Department, the Natural Resources Conservation Service, and the University of Vermont. He is a member of the Scientific Advisory Group on Birds for the Vermont Endangered and Threatened Species Committee, and he served on the Bird Technical Committee for the State’s Wildlife Action Plan. He obtained his undergraduate degree in Wildlife Biology from the University of Vermont and a master’s degree in Education from St. Michael’s College.

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