The Audubon Society of Northern Virginia (ASNV) Checklist produced in 2006 covers the Mid-Atlantic area, including Delaware, the District of Columbia, Maryland and Virginia. Given numerous changes in classification and species names since that date, this checklist needed updating. 

The goal of this project was to create an updated ASNV checklist based on species (but not subspecies) based on the current North American taxonomy and information for the area covered. The following list is presented in the taxonomic sequence used on the American Ornithological Society (AOS) Checklist of North and Middle American Birds, 7th edition, through the 58th supplement published in 2017. 

Project approach

This project began by merging the official state lists for the four jurisdictions in the region and using the information provided on the state lists to determine which species to designate as rare or accidental for the area. Because of the differences across the state lists in the information they provide, shown in Table 1 below, this approach proved unwieldy.

The checklist team therefore decided to use eBird frequency data along with the state lists to make the final determination of species to place on the list, species to be identified as rare or accidental, and species to exclude altogether.

eBird’s “Explore Data” feature provides species bar charts that depict frequency levels. The user can select the geographic area and date range, and download frequency data by week by species.

Frequency is defined in eBird as “percentage of checklists that report a species within a specified date range and region.” For example, if during a week, 20 checklists are submitted by eBird users and 10 of these checklists include Canada Geese, the frequency of Canada Geese that week is 0.50 (the number of checklists including Canada Geese divided by the total number of checklists). 

The following steps were taken to create the new Mid-Atlantic checklist:

1. Identify and obtain the relevant AOS and official state lists.

2. Download and summarize the eBird frequency data.

3. Create and apply criteria for applying the frequency measures to determine which species to include, exclude, and designate as rare or accidental.

4. Review the results from Step 3 and modify as judged appropriate.

5. Update the checklist to the most recent AOS taxonomy.

Step 1: Identify and obtain the relevant AOS and official state lists

The following lists were obtained:

1. AOS Checklist of North and Middle American Birds, 7th edition. This checklist incorporated changes through the 57th supplement (July 2016), and did not include subspecies. The list includes the AOS taxonomic sequence number, and the AOS species ID number, as well as the common and scientific names. http://checklist.aou.org/taxa/ Downloaded 7/13/2016.

2. AOS Checklist of North and Middle American Birds, 7th edition, through the 58th supplement (July 2017) Downloaded 7/26/2017.

3. Delmarva Ornithological Society, Delaware State List of Bird Species, September 1, 2015. http://www.dosbirds.org/committees/records/state-list-review-species/ Downloaded 1/22/2016. Names and taxonomic sequence follow the AOS Check-list as of September 2015.

4. Maryland Ornithological Society, Official List of the Birds of the District of Columbia, as of May 4, 2016. This list is based on the AOS checklist, 7th edition, through the 56th supplement. http://www.mdbirds.org/mddcrc/pdf/dclist.pdf Downloaded 7/25/2016.

5. Maryland Ornithological Society, Official List of the Birds of Maryland, as of May 4, 2016. This list is based on the AOS checklist, 7th edition, through the 56th supplement. http://www.mdbirds.org/mddcrc/pdf/mdlist.pdf Downloaded 7/25/2016.

6. Virginia Society of Ornithology (VSO) The Birds of Virginia and its Offshore Waters: The Official List. This list is in order given in the AOS checklist, 7th edition, through the 57th supplement, issued July 2016. http://www.virginiabirds.org/varcom/official-state-list/

Step 2: Download and summarize the eBird frequency data

eBird frequency data were downloaded in October 2016 from the Cornell Laboratory of Ornithology eBird website for 2005-2015 for the four jurisdictions. These data show for each week the total number of checklists and the frequency for each species.

The eBird data were edited to remove “domestic types”, hybrids, “sp.” cases (e.g., swan sp.) and combined species (e.g., Snow/Ross's Goose). The remaining data include 457 species.

The weekly data were summarized to show the frequency with which each species appeared for each year from 2005 through 2015, and for the entire period. The number of years in which the species was reported was also calculated. This was done using the following steps:

1. Multiply the weekly frequency measure by the total number of checklists for the week, resulting in the number of checklists on which the species was reported for the week.

2. Sum the number of checklists for all weeks in the year, and all weeks across the entire period.

3. Calculate the frequency measure for each year and the entire period by dividing the number of checklists on which the species was reported by the total number of checklists.

4. Count the number of years over the multi-year period in which each species was reported in eBird.

The resulting data were combined with information from the official state lists, resulting in a worksheet for review by the checklist team. The worksheet included 503 species, reflecting all species that appear on the official state lists. The worksheet included the following information:

Step 3:  Create criteria for applying the frequency measures

Criteria were created for applying the number of years in which the species was reported, along with status information from the state checklists. Where results seemed questionable, the eBird data was relied on more than the state status information. The DC list is disregarded in the criteria.

Rules for excluding species:

1. Listed as Accidental in VA and not on other state lists, and with zero eBird reports during 2005-2015.

2. Listed as Part 1 on MD list, with review code 2 (reviewable anywhere in MD), not on other state lists, and with zero eBird reports during 2005-2015.

3. Listed as Part 1 on MD list, with review code 2 (reviewable anywhere in MD), not on DE list, Accidental on VA list, and with zero eBird reports during 2005-2015.

4. Listed as Part 1 on MD list, with review code 2 (reviewable anywhere in MD), not on VA list, reviewable on the DE list, and with zero eBird reports during 2005-2015.

5. Listed as Part 3 (questionable origin) on MD list, not on other state lists, and with eBird reports in zero or 1 year during 2005-2015.

6. Listed as Part 3 (questionable origin) on MD list, not on DE list, Accidental on VA list, and with eBird reports in zero or 1 year during 2005-2015.

7. Listed on DE list as reviewable, not on other state lists, and with zero eBird reports during 2005-2015.

8. Listed on DE list as reviewable, not on MD list, Accidental in VA, and with zero eBird reports during 2005-2015.

9. Species extirpated in all states where listed.

10. Extinct species.

For the species not excluded:

1. Accidental species
     a. Listed as Accidental in VA.
     b. Not on VA list, reviewable DE and/or listed as Part 1 with review code 2 (reviewable statewide) in MD, and with eBird reports in zero to 4 years during 2005-2015.

2. Rare species
     a. Listed as Rare on VA list.
     b. Not on VA list, reviewable DE and/or listed as Part 1 with review code 2 (reviewable statewide) in MD, and with eBird reports in 5 or more years during 2005-2015.

3. Introduced species
     a. On VA list as Category 5.

Step 4: Review the results from Step 3 and modify as judged appropriate

The checklist team reviewed the resulting list and made revisions relying on eBird data. For example, a species may be listed on the VA list as accidental, but had zero eBird reports for 2005-2015. In the review, such species were generally excluded.  

During the review, the team considered that the eBird data are what birders report to eBird, rather than data from controlled surveys. This means that areas that are infrequently or never visited by eBird users are not well represented, and that birders may infrequently report nocturnal sightings. Thus, some species may be under-represented, such as owls and nightjars. Thus, the team made some judgmental decisions that over-rode the strict application of the criteria. The team also decided to present the accidental species as a separate list at the bottom of the new checklist, rather than including the accidentals in the main checklist.

The resulting list included 372 species to appear on the main checklist and 82 species to be shown as accidental. Forty-nine species were excluded.

Step 5: Update the checklist to the most recent AOS taxonomy

The AOS published taxonomic changes in July 2017, as the 7th edition, 58th supplement. Changes affecting the Mid-Atlantic region included:

• Deleted Thayer’s Gull, which was lumped with Iceland Gull

• Changed spelling of LeConte’s Sparrow (deleting the space in “Le Conte’s”)

• Changed the taxonomic order.

The Mid-Atlantic checklist was matched to the new AOS list, and sorted in the new AOS order. The final list includes 371 species on the main list and 82 accidental species listed separately.

The Checklist Team

The checklist team was led by Dixie Sommers, with assistance from Tom Blackburn, Greg Butcher, Greg Fleming, and Laura McDonald. Most of the work was conducted from mid-2016 to early 2017, and the update to the most recent AOS taxonomy was done in July 2017.

Table 1. Species Status Codes Used on the State Lists