Audubon North Carolina has 10 amazing chapters across the state who help put a local focus on bird preservation and conservation issues. In this special blog series, we’ll focus on a chapter each month to learn more about their history, what they are working on, and to increase the statewide understanding of special ecosystems and habitats. Each month will include a series of posts about each chapter including a post from our biologists that will share a unique research project that is happening in the chapter’s geographic footprint.
This month, we get to know the Elisha Mitchell Audubon Society http://emasnc.org/. Please welcome guest blogger and EMAS president Tom Tribble, as he details former president Charlotte Geodsche’s work studying the Cerulean Warbler song types near Asheville’s Bull Creek IBA. Charlotte served as the EMAS chapter’s president from 2007 to 2011.
Drive the Blue Ridge Parkway between mile markers 372 and 377 on any day from mid-April to early June and you are likely to see Charlotte Goedsche standing beside the road looking upward and pointing a parabolic shaped disc at the trees.
In 1998, long time EMAS member Charlotte Goedsche began monitoring Cerulean Warblers along the Blue Ridge Parkway north of Asheville as part of Cornell University’s Cerulean Warbler Atlas Project. In 2000, the area was designated the Bull Creek IBA, which was subsequently adopted by EMAS. Charlotte served as President of EMAS from 2007 through 2011.
In 2005, she began recording male Cerulean’s songs to distinguish between individuals and to map each male’s territory. She relies on territory mapping and song analysis of recordings of individual male Ceruleans. After downloading the recordings, she analyzes the sonograms with Raven Pro sound analysis software. Each Cerulean has from one to three “song types,” which serve as a calling card. Combining the maps with song analysis allows Charlotte to identify individual territorial males, even though these birds are not banded.
The total number of Cerulean song types is around 20, and there is some variation even within the repertoire of an individual bird. Therefore, Charlotte cannot state with certainty that a bird that sings only one song type is a returning bird. However, when dealing with a bird with two song types, the probability of that bird being identical to one from the previous year, with the same two song types at the same site, is mathematically greater.
Analysis of the sonograms of two different song types (see sonograms below) of a Cerulean at the north end of Tanbark Ridge Tunnel in April 2012 indicate that the songs are identical to the two songs of a bird that spent the 2010 and 2011 breeding seasons at this location. Since the birds in this population are not banded, she cannot ‘prove’ that any have returned from a previous season, but the sonograms strongly suggest that this is a returning bird. Neither the 2010 nor the 2011 nor the 2012 bird had a white supercilium, meaning that they all were adults in at least their second year. If correct, this bird must have hatched no later than 2008.
A Cerulean recorded in 2009 bird likely sang the same two song types, although Charlotte did not get enough definitive recordings of that bird do be certain. If the bird in question really was at the tunnel in 2009, it would be the longest tenure of a Cerulean in this IBA during Charlotte’s study.
Charlotte submits regular reports to the National Park Service and to Curtis Smalling, Director of Land Bird Conservation for Audubon North Carolina. She anticipates ultimately publishing the results of her long time study.
Audubon North Carolina oversees statewide conservation projects year-round. To donate to this and other efforts protecting birds, click here.