Vagrant kingbirds such as Tropical, Couch’s and Cassin’s have all been recorded in the north-east and it is only a matter of time before one of these “Western” kingbirds in Connecticut turns into something a bit more exciting.
While Western Kingbird is the expected species, Cassin’s has been recorded in Massachusetts in 2010 (https://www.flickr.com/photos/bonxie88/6686022777/in/photostream/)
and recently as last week in Brooklyn, although this was a one-observer sighting and couldn’t be refound.
Pictures clearly solidify the identity (https://www.flickr.com/photos/123166253@N05/sets/72157646979944483/); the second record for NYS after one at Montauk in October 2007 ( http://citybirder.blogspot.com/2014/11/new-brooklyn-rarity.html)
The Mass bird was mis-identified as a Western by virtue of its tail pattern, which was blackish and showed prominently white outer webs to the tail feathers, a key id feature of Western. That Cassin’s can show this too means that any yellow-bellied kingbird with a blackish tail and white outer edges may not necessarily be a Western.
A reported Western Kingbird in Bridgeport, without any details of other potential species being systematically ruled out, set off the spidey senses. Questioning several observers, it seems the bird was distant but the ”white tail edges were apparent” The only pictures we saw seemed somewhat ambiguous – indeed the darkness of the head and tail pattern in one image suggested better photos need to be obtained to rule out Cassin’s. Further images revealed the bird to be a Western, as reported, but it spotlighted some tail features that needed to be expounded upon should observers be faced with a fall, yellow-bellied kingbird.
So, just because it has pale outer tail feathers it doesn’t automatically make it a Western (see the Mass individual). So what should you key into when you chance upon a distant yellow-bellied kingbird?
- Bill size and shape and tail seem to be the two main features to concentrate on. Calls are also invaluable in separating kingbirds, so recording and/or a clear description of the call is important in identifying and documenting the record from a historical point of view.
- Any yellow-bellied kingbird with a blackish tail that is darker than the wings, is either a Western or a Cassin’s.
- Both Western and Cassin’s show whitish tail sides, but Cassin’s often lacks this and has pale tips to the tail forming a pale terminal band. They are typically more obvious and include the entire outer vane of the outer tail feather in Western. Sometimes in the field this may not be obvious, so continued observation of an individual may be required to determine the presence and amount of white in the tail.
- Any kingbird that has a paler brownish tail, that is concolorous with the wings is likely a Tropical or Couch’s. Note that some Tropicals can show paler edges to the outer tail feathers, but this is narrower and less well-defined that Western. Tropicals in particular seem to show a disproportionately long and notched tail.
- Tropical and Couch’s both show a long, broad and hooked bill tip, larger than either Western or Cassin’s but sometimes, bill size and shape can be hard to determine on lone individuals.
- Cassin’s and Western have a smaller bill, but compared to Western, Cassin’s have a short, but deep-based bill, often with a curved culmen that gives the bill a stouter, more conical-appearance.
So, a distant kingbird that has an obvious blackish-tail, darker than the wingtips, should get you into the Cassin’s/Western camp and a bird that has a tail concolorous with the wingtips should get you thinking about Tropical/Couch’s.
Separating them from here requires more observation about plumage and how dark the grey areas are on the head, underpart color and tail pattern. This post isn’t meant for covering that in detail, but I found a similar and more in-depth look at this problem by Kevin McGowan here at http://www.birds.cornell.edu/crows/kingbirdsX.htm