Wildlife Indicators :: Animal Diversity :: At-risk species :: Breeding bird survey :: Significant Natural Heritage Areas
Landscape Habitat/Indicator Guilds :: Biodiversity and Wildlife Habitat Assessment

Breeding bird survey

What is this?

The annual Breeding Bird Survey monitors the status and trends of birds in North America. The survey is a collaborative effort with the U.S. Geological Survey’s Patuxent Wildlife Research Center and the Canadian Wildlife Service’s National Wildlife Research Centre. Every year, thousands of participants collect data on routes throughout North America. Breeding Bird Survey statisticians compile this information to give conservation groups, scientists, and universities population data on more than 400 bird species. The breeding bird survey was started in 1966 and each June, more than 3,500 routes are surveyed by experienced birders.

Why is this important?

We selected a few species with specific habitat needs to see if their numbers have declined over time. Also, we selected species that are more tolerant of human development to see if their numbers have increased over time. This approach could easily be expanded to include all observed bird species on the Triangle routes to measure an increase or decrease in overall bird diversity in the region . Focusing on birds with specific habitat requirements is important because a decline in these birds could be attributed to a loss of habitat. This information could then be used to target conservation efforts to save the remaining habitat for these species.

What does this measure show?

The breeding bird survey shows a change in observed birds over time for the designated routes. Many of these routes have been documented every year since 1966 when the program started. Observers travel the same routes every year and document the number of different bird species they find. We chose to look at the Durham route, Jordan route and the Youngsville route for this analysis. The Youngsville route is just outside the Triangle in Franklin County, but it was the closest route to the Triangle that had data for more than 6 years. Future work could include the Goldston route that is in the Triangle, but currently only has data for the past 6 years. The breeding bird survey data for the three routes showed a decline in certain bird species that are sensitive to human development like the field sparrow and the acadian flycatcher. The survey data also showed an increase in other birds like the American crow and the house finch that are more tolerant to human development.

Field sparrow
photo by Michael J. Hopiak
Acadian flycatcher
photo by Greg W. Lasley
American crow
photo by Steve Allen
House finch
photo by Steve Allen

Species examined

Field sparrow - Spizella pusilla

Field Sparrow - Durham Route
Field Sparrow - Jordan Route
Field Sparrow - Youngsville Route

Field sparrows forage and nest near the ground in fields and open woodlands. As farmland is converted into suburbs the field sparrow’s preferred habitat is threatened, leading to a decline in much of its range. The field sparrow breeds in old fields and woodlands and winters in fields and in the forest edges. Field sparrows are year round residents in the Triangle. The population of field sparrows in the U.S. is thought to be around 5.8 million, down from about 18 million 40 years ago. Numbers for the field sparrow on all three of the Triangle routes have declined.

Acadian flycatcher - Empidonax virescens

Acadian flycatcher - Durham Route
Acadian flycatcher - Youngsville Route
The Acadian flycatcher prefers heavily wooded deciduous bottomlands, swamps, and riparian thickets. The Acadian flycatcher is fairly common through most of its range and is expanding its range in the Northeast. It is considered an area-sensitive species that is vulnerable to forest fragmentation. Numbers for the Acadian flycatcher on all three of the Triangle routes have declined.

American crow - Corvus brachyrhynchos

American crow - Durham Route
American crow - Jordan Route
American crow - Youngsville Route

American crows are common throughout all of North America and are year round residents throughout most of the United States. Crows thrive around people and eat everything from earthworms and insects to garbage and carrion. The American crow is a highly adaptive bird which is one reason its numbers have increased in areas of human development. Increases in American crow populations can lead to more competition with less aggressive bird species. Numbers for the American crow have increased on all of Triangle routes.

House finch - Carpodacus mexicanus

House finch - Durham route
House finch - Youngsville route

The house finch was introduced in New York in the 1940s and quickly surpassed the house sparrow (another introduced species) to become the most widely distributed songbird in North America. Competition with the house finch is believed to have contributed to the decline in the numbers of house sparrows. The house finch is abundant over most of North America and can be found in a range of habitats, including suburban yards. The house finch frequents bird feeders and can be found in flocks of 50 or more birds. A rise in the number of house finches can spell trouble for native species that compete with the house finch for food and habitat. Numbers of house sparrows have declined in all three Triangle routes while the house finch numbers have risen.

Limitations and Further Research

The BBS routes are randomly selected by the national office and there are only three current routes in the Triangle. The Goldston route has only been surveyed for the last 6 years, so we chose the Youngsville route in Franklin County because it is the next closest route to the Triangle and has been surveyed for a greater period of time. Combining this data with other bird surveys like the annual Christmas Bird Count could lead to a better understanding of what is happening to the number of habitat sensitive bird species in the region and the overall bird population.

Authors Steve Allen, Jessica Stocking and Amanda Willis :: N.C. State University :: 2010.05.07

Jacquelyn Wallace :: North Carolina Wildlife Resources Commission
Dr. Dean L. Urban :: Duke University
Dr. Christopher Moorman :: N.C. State University

Technical Notes

Data from the USGS annual breeding bird survey were reviewed for the Durham, Jordan and Youngsville routes. The data were accessed online at http://www.mbr-pwrc.usgs.gov/cgi-bin/rtena07a.pl?63 and the USGS graphs over time were downloaded for the selected species. Data are updated annually by the USGS and can be monitored and updated by conservation organizations.

Wildlife Indicators :: Animal Diversity :: At-risk species :: Breeding bird survey :: Significant Natural Heritage Areas
Landscape Habitat/Indicator Guilds :: Biodiversity and Wildlife Habitat Assessment