Does that bird count?

Whether or not a bird “counts” on your birding list seems like a simple enough issue. The American Birding Association, the mediator of counting rules for North America birders, has a committee that establishes which populations do and do not count as distinct species. The ABA carefully follows the American Ornithologists’ Union Committee on Classification and Nomenclature. So, all one need to do is to check the published ABA list to see if a bird counts or not, right? If only it were that easy.

A significant part of the “does count/doesn’t count” discussion relates directly to species concepts and whether taxa like Audubon’s Warblers are subspecies or full species. I don't lack opinions with regard to where species boundaries fall, but I’ll leave that discussion for future blogs. Here, I want to consider when and where invasive avian species are countable.

Two recent birds that I observed and photographed in Alabama highlight the difficulties concerning the countability of invasive bird species. In September, following up on a report from Ron Kittinger, I went to see Mute Swans near Shelby Alabama. This was actually a swan family with the adult parents and four immature-plumaged offspring. These swans were not anyone’s pets. The lived in a pond away from any human dwelling, they could fly, they retreated from people, and they acted like wild birds.

A family of Mute Swans on a pond near Shelby, Alabama. It is an open question regarding the countability of Mute Swans in Alabama, although they certainly are countable in states to the north.

In my view, unless there is compelling reason to believe otherwise—such as leg bands or a close association with a house or farm-- Mute Swans in Alabama should be presumed to be wild birds, just like Canada Geese and Mallards in wild-type plumage are presumed to be wild birds. These swans represent the edge of the rapidly expanding range of Mute Swans in North American. Mute Swans have been ABA countable in the eastern United States for decades, with centers of abundances in Michigan/Ontario and the NE US. But look at the ebird map below. As you would expect with any expanding introduced population, the are peripheral populations of Mute Swans expanding outward from their centers of abundance including to the south. Alabama shows no ebird records of Mute Swan, but from my daily ebird alerts, I know that there are ebird-submitted records of breeding Mute Swans in Alabama, including the Shelby Mute Swans that Ron Kittinger and I and others entered into ebird . I suspect that ebirds editors are not permitting Mute Swan records to enter into the database. If that is true, then it is shortsighted because it distorts the record of range expansion for the species. I'll be submitting the Mute Swan to the Alabama records committee for consideration as a countable species.

Ebird map of Mute Swan sightings through 2016. Like many invasive species, Mute Swans are underreported away from centers of abundance.

Two weeks ago, I ran into another invasive waterfowl species in Elmore County, Alabama, northeast of Birmingham. This time the bird was an Egyptian Goose, a species that is endemic to Africa but was introduced to Florida. It now has a large, growing, and ABA-countable population in Florida, mostly south of Gainesville.

An Egyptian Goose with Canada Geese in Elmore County Alabama on 6 November 2016. This is potentially a first documented record of a wild Egyptian Goose in Alabama, but like any rare bird report, this Egyptian Goose report will have to be considered by the Alabama Rare Birds Committee.

Look at the ebird map for Egyptian Goose reproduced below. This is a population of birds that has rapidly spread through peninsular Florida largely via dispersal from the Miami area, so it would hardly be shocking if dispersing individuals start to turn up in neighboring states like Alabama.

Ebird map of Egyptian Goose through fall 2016. We can expect to see vagrant Egyptian Geese dispersing from Florida throughout the SE U.S.

Purple Swamphen is another invasive species that I expect to see in Alabama wetlands within the next couple of years. That species has been increasing explosively in wetlands throughout Florida, and birds are being reported farther and farther north in Florida. The extensive wetlands at Eufaula NWR in SE Alabama seem ideal for Swamphens, and I expect to see one any day at Eufaula. I think a vagrant Purple Swamphen will be added to the Alabama species list much more readily than either of the waterfowl mentioned above, because there is a greater possibility of waterfowl being released into the wild. But I will argue that in the case of the Mute Swans and Egyptian Goose, the circumstances or range expansion and behavior of the birds points to a dispersal without human assistance.