kevin's id tips
Tropical and Couch's Kingbirds
Couch's Kingbird (small-billed) (L) and Tropical Kingbird (R)
These two very similar kingbirds have traditionally been considered inseparable in the field unless heard calling. Recent study has given us a few structural guidelines that are useful in separating some silent birds.
Physical Features and Vocalizations:
Some Tropical Kingbirds show noticeably longer and flatter bills than Couch’s Kingbird, which has a shorter, deeper bill on average. Problems occur with smaller-billed Tropical Kingbirds that have bills which closely resemble larger-billed Couch’s Kingbirds.
Head shape is fairly reliable feature that can be used along with bill size/shape to ID some silent birds. Many Couch’s have steep foreheads that rise to a proportional rounded crown versus a shallow forehead on Tropical that extends to a flatter crown and deeper head profile from front to back. Usually this head shape on Tropical corresponds to birds with a larger, more obvious bill and noticeably forked tail, and a combination of these features results in a safe ID of Tropical Kingbird.
Tail shape is another helpful feature for separating these birds. Some Tropical Kingbirds have noticeably forked tails, while some Couch’s show mostly square-tipped tails, like the bird in the comparison photo. This feature combined with the extremes of bill length and shape can be used to identify a good number of silent kingbirds. Silent birds that don’t exhibit extreme bill size and shape have slightly forked tails are best left unidentified.
Vocalizations of these two species are distinctive, with Tropical giving a rapid series of high-pitched notes that rises abruptly near the end. This call is similar to running your finger along a metallic comb from the thick to thin teeth, and has a trill-like quality. Couch’s gives a series of slower kip-kip notes or a plaintive, descending queer.
Plumage and Bare Parts Details:
Both species are essentially similar in plumage, though Tropical usually shows a darker mask and greener back, but these details are variable and often not helpful.