Bewick's Swan: An Ohio First

 

A quintet of Tundra Swans (Cygnus columbianus) prepares for landing.

I attended the annual Ohio Bluebird Society's annual meeting last Saturday, March 2, to speak about moths. Little known fact: The majority of the Eastern Bluebird's non-winter diet is moth caterpillars. Shauna and I had a great time, met lots of people, and I saw scads of friends that I haven't seen in a while. The Society is quite active and about 140 people were in attendance.

Afterwards, Shauna and I took the long way home, in order to visit Killbuck Marsh - one of the largest interior wetland complexes in Ohio. Killbuck lures scads of migratory waterfowl in spring, including large flocks of Tundra Swans (Cygnus columbianus). On February 23, Josh Yoder located a "Bewick's" Swan in a large flock of Tundra Swans, and I'd wanted to get up there to see it ever since. That bird was our primary target on this trip, and it wasn't hard to find, especially as many birders were on the scene.

The Bewick's Swan is now (mostly) considered to be a subspecies of the Tundra Swan (Cygnus columbianus bewickii). However, it has been considered a separate species in the past, and the American Ornithological Union didn't lump it into the Tundra Swan until 1983. While most authorities dealing with avian nomenclature and taxonomy consider it to be a subspecies at present, Avibase separates the two.

A pair of Tundra Swans drops in, landing gear extended. Don't expect National Geo-caliber imagery in this post. The flock of Tundra Swans that our target fraternized with was a LONG way across the marsh. Maybe 200 yards or so, so it took some photographic oomph to even get the documentary shots that I did. I used my Canon 800mm coupled with a 1.4x extender (1120mm) and that's generally not the ticket for sharp vibrant shots on a heavily overcast day. Nonetheless, the rig did allow me to capture diagnostic details of the bird in question.

As always, click the photo to enlarge

As a point of comparison for the bird to follow, here's the nominate subspecies of Tundra Swan - the subspecies that occupies North America and occurs in Ohio during migratory periods. That's an adult on the left, with a juvenile facing away from the camera. Note the classic small yellow teardrop on the bill, in front of the eye. While some individuals can have all black bills, a little fleck of yellow as on this bird is pretty typical.

One of these swans is not like the other. Specifically, the bird second from right. Even from afar, the big yellow blotch on the bill stands out. A typical Tundra Swan shouldn't (couldn't?) ever show that much yellow.

Here's the range map of the Tundra Swan, courtesy of the Cornell Lab of Ornithology Birds of the World website (I'm a longtime subscriber, and anyone with a serious interest in birds should consider a subscription, found HERE).

For the most part, all of the birds represented in America are Tundra Swans, and those in Eurasia are Bewick's Swans. A rub: The nominate subspecies of Tundra Swan (the North American birds) also breed in eastern Siberia, and hybridization between the two subspecies occurs there.

Here's the best that I could do to photographically capture the Ohio Bewick's Swan. While that big splotch of yellow exceeds anything that could, or at least should, be present on a Tundra Swan, classic Bewick's Swans can show even more yellow. On some/many/most Bewick's, that yellow forms an even larger blotch, and can extend across the top of the bill to connect the two side patches. Whether the yellow marks increase in size with age, I do not know.

Here is a germane quote from the Bird's of the World Tundra Swan account:

Birds appearing identical to the Palearctic form (C. c. bewickii) reported occasionally in w. North America (Alaska, Alberta, Saskatchewan, Oregon, and California). Some of these are likely true bewickii, but others may be bewickii x columbianus intergrades from e. Siberia, or even variants of columbianus with excess yellow on the bill. The occasional bewickii reported farther east in North America may represent escapees from captivity.

To address the latter point about escapees: While many species of waterfowl are kept - sometimes fairly commonly - in captivity, and occasionally escape, I don't think that's the case here. A search, less than comprehensive, admittedly, for Bewick's Swans for sale revealed nearly no sellers, and I've not personally heard of this subspecies being peddled by waterfowlers, at least in this part of the world. Also, the appearance of the Ohio bird syncs perfectly with the major northward push of Tundra Swans, and it is fraternizing with them. Presumably a wayward Bewick's Swan, prone to vagrancy, would also wander at this time of year. And more records have occurred in the east since that quoted paragraph above was written. eBird records about a dozen records to date from the eastern U.S. and Canada.

The bigger question involves hybridization between the subspecies, and definitively answering that is well beyond my paygrade. While I've seen many thousands of the nominate Tundra Swan subspecies, I've got next to no experience with Bewick's Swan. I think it would be very helpful to get images of this bird to someone who sees lots of Bewick's Swans and understands their variability, and especially the appearance of hybrids between the subspecies.

NOTE: It is always helpful to remember that "species" are merely a human compartmentalization scheme. All species are in a constant state of evolution and where one draws the line of separation between two very similar "species" or especially "subspecies" is almost always somewhat arbitrary.

Any way one slices this swan, it was a great find by Josh Yoder, and the bird offers interesting food for thought, in addition to its undeniable curb appeal. It is an apparent first state record for Ohio, and one of very few reports anywhere in eastern North America.