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Appalachian National Scenic Trail Breeding Bird Baseline

Figure 1. Distribution of eBird observation records within the Appalachian National Scenic Trail HUC10 Shell.
Figure 1. Distribution of eBird observation records within the Appalachian National Scenic Trail HUC10 Shell.


Breeding birds provide a useful biotic indicator to assess the effects of habitat fragmentation and habitat loss, and are a highly visible and charismatic group. They are commonly viewed as an optimal faunal group to monitor because they are easily and inexpensively detected and identified, and because accounting and managing for bird species with various ecological requirements promotes conservation strategies at the landscape scale.

And, perhaps most importantly for entities like the APPA monitoring program that have few resources to collect new data, there are many existing avian datasets available. For this web page, we relied on data from eBird, an online database that is part of the Avian Knowledge Network (AKN) that makes available their own data as well as data from a wide variety of other sources. Figure 1 shows the distribution of data available from eBird in the vicinity of the APPA, with each dot representing an independent observation -- nearly 2.5 million since 2001. Coverage extends along the entire trail, but Maine and the portion of the APPA from central Virginia southward appear to have a lower concentration of observations compared to the central portion of the APPA (Figure 1).


We began by downloading a complete dataset from eBird. This dataset was subsequently clipped to the HUC10 shell to establish a geographic scope for the project. The HUC10 shell is the “outer” boundary of all HUC10 hydrologic units that are within 5 miles of the APPA land base. HUC10 units (watersheds) are defined at the fifth level of the Hydrologic Unit Code system, with each being given a discrete 10-digit code. The hydrologic unit system was developed by the USGS and subsequently modified by the Natural Resource Conservation Service (NRCS). The HUC10 shell, or the general frame of reference used to establish an area of interest around the APPA, is the "outer" boundary of all HUC10 hydrologic units that are within 5 miles of the APPA land base. There are 177 individual HUC10 hydrologic units within this shell. Though they are termed watersheds, Omernik (2003) explains that hydrologic units are not always true watersheds and that some hydrologic elements contained within the HUC10 shell may not include all upstream components of a true watershed. We use the HUC10 because it incorporates all areas of immediate interest to APPA resource managers as well as areas that are more distant but potentially of great ecological similarity. While the HUC10 shell does not guarantee that projects or data within it will be of interest, or that data and activities beyond it are not of interest, it does provide a starting point and some degree of guidance when attempting to determine if data or activities are worthy of further consideration.

Figure 2. Cumulative eBird records.
Figure 2. eBird cumulative records over time.

After identifying the geographic bounds of the dataset, we further filtered the dataset to additional ways. First, we excluded data collected prior to 2001. We selected 2001 because that was when the volume of observations increased markedly (red line, Figure 2). While observations prior to 2001 may be valid, we felt that it was important to constrain our view to a period when most observations were made. Second, we excluded "casual observation" data to minimize potential for sampling bias.

We combined the eBird observation data with information from Partners in Flight, the North American Bird Conservation Initiative and the National Audubon Society to develop listings of priority species known to occur on, or in close proximity to the APPA. We have also generated listings of species according to state and ecoregional subsection (Figure 3). The different lists are accessed by "clicking" on the desired item. When a new list is selected, the map will change to reflect the geographic scope associated with the list. Additional information may be obtained about the source of the list by clicking the list heading, and details about the species appearing on the list can be obtained by clicking on the common name.

Birds Along the Appalachian National Scenic Trail:


Ecological SubSections:


Additional Information

The bird listings (Figure 3b) include three elements: rank, common name, and records.

  • Rank is based on all species for the entire trail. So, a species that is ranked #1 would be the most commonly reported species throughout the HUC10 region, whereas a species ranked #400 would be the 400th most frequently reported species. The numerical rank does not change when you change the list you are viewing. For example, you might find that the most common species throughout the entire region (American crow) is less common in a more constrained geographic area (e.g., Pennsylvania), but the rank associated with that species is retained even though it might appear further down the geographically constrained list in descending order by the number of observation records for that geographic area.
  • Common name is the accepted common name for a given species.
  • Records are the number of entries (observation records) there are for a given species within the specified geographic area.

These listings are most valuable for identifying species known to occur along the APPA and the number of observations may offer some insight into relative abundance. For example, a species with 10,000 observations is likely to be present and detectable during some portion of the year and is almost certainly more abundant within a specified geographic area than a species with only 50 observation records. However, it would be wrong to suggest that the American crow is the most abundant bird on, or near APPA solely based on these data without some way to standardize the way all observations within the dataset were obtained. The American crow could be the most abundant, the most detectable, the most recognized bird, or a combination of these possibilities. While the number of observations may not definitively state which birds are most abundant, it is reasonable to suspect that a bird with many observations is either more common or easier to detect than a bird with fewer observations.

Priority Listings

Partners In Flight

Partners In Flight describes itself as "…a cooperative effort involving partnerships among federal, state and local government agencies, philanthropic foundations, professional organizations, conservation groups, industry, the academic community, and private individuals…" with a mission to help species at risk, keep common birds common, and form partnerships for birds, habitats, and people. The purpose of the Partners In Flight watch list is to identify migratory birds that are in most need of conservation action. Details on the type of conservation action advocated by Partners In Flight can be obtained from the Partners-in-flight web page.

Audubon Target List

The Audubon Target List helps to identify the species of birds that are in greatest conservation need. Audubon develops lists according to flyway. For the APPA, we used the eastern flyway.

Birds of Conservation Concern by Bird Conservation Region

The North American Bird Conservation Initiative describes a bird conservation region (BCR) to be: "…ecologically distinct regions in North America with similar bird communities, habitats, and resource management issues…" In the case of the APPA, two BCR's directly intersect the footpath (14 and 28), while three (13, 29, and 30) are within the HUC10 shell but do not intersect the footpath. Species shown on each BCR list are those deemed by the U.S. Fish and Wildlife Service, in the "Birds of Conservation Concern" report (U.S. Fish and Wildlife Service 2008), to deserve the " …highest conservation priorities…."

Sources Cited

Cornell Lab of Ornithology. 2012. eBird. Avian Knowledge Network. Ithaca, NY. (Accessed: 19 December 2012).

U.S. Fish and Wildlife Service. 2008. Birds of Conservation Concern 2008. United States Department of Interior, Fish and Wildlife Service, Division of Migratory Bird Management, Arlington, Virginia. 85 pp. [Online version available at ]

Omernik, J.M. 2003. The Misuse of Hydrologic Unit Maps for Extrapolation, Reporting, and Ecosystem management. Journal of the American Water Resources Association. (JAWRA) 39(3):563-573.