Odd Kingbirds at Metropolitan Park

To file under suspicious birds: Jan Axel Cubilla and Osvaldo Quintero saw a flock of 20 odd-looking kingbirds at the Metropolitan Nature Park last sunday. Quoth Jan Axel:

La verdad es que esos tiranos se ven algo raros. En primer lugar, ya antes habia visto muchos Tropical Kingbirds reunidos en árboles con frutas, pero no tantos (conté 20 por lo menos). Además, todos me parecían pequeños sin excepción, tanto así que la impresión general que me dieron fue la de una bandada de Tiranos Norteños. También me parecieron muy "nítidos", lo cual confirmo en las fotos (casi sin oliva en el pecho, cabeza bastante pálida acentuando la "máscara"). Las fotos sólo están cropeadas, no les he cambiado nada del color, ni contraste ni nitidez. Verifiqué algunas fotos en la web de el Tirano Gorgiblanco (Tyrannus albogularis) de suramérica (el cual es migratorio) y la verdad me han quedado ganas de regresarme a ver si todavía están allí para salir de mis dudas. Creo que voy mañana de nuevo para ver.

What do you think? Oddball Tropical Kingbirds or Panama's first White-throated Kingbirds? We'll keep you posted of any developments.

Some of the comments:

Wow. I'm definitely no expert on South American tyrannids, but in a quick look, the photos sure don't suggest Tropical Kingbird -- nor, to my eyes, White-throated Kingbird. This is based on very little experience, I admit, but the compact shape, relatively short tail, small-looking bill, and pale edgings on the coverts all seem more suggestive of Snowy-throated Kingbird (T. niveigularis). It would be good to have photos from more different angles. Thanks for sharing the info on these! Sounds like you guys have a lot of interesting things going on in Panama these days. —Kenn Kaufman

For what its worth. I doubt that they are anything but odd looking (i.e. recently molted or young) Trop Kings.....we have birds in the collection that differ by 20 grams (from 30 - 50) with quite variable plumage, etc. Years ago folks including STRI people looked at the genetics of Swainson's Flycatcher (Myiarchus) and it was a total mess with cryptic species that have been overlooked because of plumage similarity. I sometimes wonder about Tropical Kingbirds, because so many of us overlook them completely in the field. However a study this year from Bolivia found no genetic variation between migrants and residents, though they could be distinguished in the hand morphologically. —AmazonMatt