An update from our Bird Atlas Coordinator, by Spring Ligi
For the past five years, local citizen scientists have been observing and listening to birds in their backyards and throughout Loudoun County, acquiring a unique and intimate glimpse of our feathered friends. Did that cardinal have nesting material in her mouth? Is that the deep, soft hoots of a dueting pair of Great Horned Owls? These and other behaviors were documented on field cards and entered into an online database hosted by the USGS Patuxent Wildlife Research Center. The results of this year-round Bird Atlas, lead and funded by the Loudoun Wildlife Conservancy, provide a comprehensive list of breeding and non-breeding birds in Loudoun and information on their distribution. The results will help identify and protect important bird areas and provide insight into population changes over the past 25 years and into the future.
The Bird Atlas was quite an undertaking, with 85 enthusiastic Loudoun Wildlife Conservancy atlasers volunteering almost 6,000 hours in the field and reporting more than 64,500 sightings. 263 species were documented between April 2009 and March 2014, with 104 of these species confirmed as breeding in Loudoun County. Table 1 below provides a snapshot of the overall results, including a breakdown of breeding versus non-breeding birds and comparisons with data from the 1985–1989 Virginia Breeding Bird Atlas (BBA).
Where did we find the most species? Surprisingly, the top five blocks with the most species were in eastern Loudoun, which, unlike the somewhat rural western half of the county, is undergoing rapid development. An astounding 190 species were documented in the Brambleton area and also in southern Leesburg (areas in and around Banshee Reeks Nature Preserve). The Sterling area, including Algonkian and Bles Parks, proved to be another rich birding area, hosting over 165 species. One possible explanation for why these more urbanized areas are so productive is that the birds are forced into smaller pockets of suitable habitat, making them easier to observe and document.
One exciting outcome of the Bird Atlas is a new and improved Birds of Loudoun Checklist. Significant updates were made to the original checklist, including the addition of new species and breeding statuses, adjustments in seasonal occurrence and relative abundance, and updates in taxonomic order. The list now includes 305 bird species identified in the county through March 2014, with over 120 reported breeders. To obtain a copy of the checklist, come to one of the Loudoun Wildlife Conservancy’s bird walks or download the list from the Loudoun Wildlife website.
Additional products from the Bird Atlas will include a summary article, species accounts, comparisons with the 1985-1989 Virginia BBA, and identification of important bird areas throughout the county. Identifying important bird areas will allow Loudoun Wildlife Conservancy and other local conservation groups to design strategies to protect the birds and other wildlife within these areas.
How have the birds changed in Loudoun over the past 25 years? Who are the “winners” and the “losers”? These are some of the intriguing questions we are beginning to answer with the Bird Atlas data. Two species whose stories stand out are the Bald Eagle and Northern Bobwhite. Bald Eagles were confirmed as breeding in seven atlas blocks and observed in 52 of the 73 blocks (Figure 1). These results provide a striking contrast to the 1980s Virginia BBA, which did not report any breeding Bald Eagles in Loudoun County. Their successful comeback can be directly attributed to the banning of DDT and placement of this species on the endangered species list. Conversely, the Northern Bobwhite is a species that has declined severely throughout the county over the past 25 years. Evidence of at least possible breeding was reported in only 19 of the 73 atlas blocks, which is down significantly from 61 blocks in the 1980s Virginia BBA (Figure 2). Their decline can be attributed to habitat loss and degradation resulting from development in our rapidly growing county, as well as changes in agricultural practices throughout their range.
We’ve only just begun analyzing this fascinating Bird Atlas dataset. Check the website (www.loudounwildlife.org/Bird_Atlas.htm) for more information and stay tuned in the coming months for distribution maps, species accounts, case studies, and additional atlas comparisons!
Table 1. Overall Bird Atlas Results
| Total species | 263 |
| Confirmed breeders | 104 |
| Confirmed and Probable breeders | 117 |
| Confirmed, Probable, and Possible breeders | 120 |
| Migrant only species | 77 |
| Winter species | 66 |
| Year-round species | 68 |
| Average species per block | 110 |
| Average hours recorded per block | 83 |
| Breeding birds documented in Loudoun in Loudoun Co. Bird Atlas but not 1980s Atlas | 14 |
| Breeding birds documented in Loudoun in 1980s Atlas but not Loudoun Co. Bird Atlas | 7 |