Just as birders in temperate North America have to deal with the kinglet-warbler identification conundrum (with the Hutton’s Vireo thrown in for good measure in some places), we birders in Costa Rica are confronted with the tyrannulet-warbler scam. It goes like this:
At some subtropical site in Costa Rica, a tiny bird flits into a nearby bush. Its hyperactive attitude is both intriguing and almost as annoying as the itsy bitsy black flies that menace your bare arms. As you spray another nasty dose of plastic-disintegrating DEET onto your vulnerable appendages, the little bird suddenly pops into view. Having become aware that a lot of these tropical birds allow for just one look before vanishing into the dense foliage, you let the DEET drop while simultaneously reaching for your trusty binos and get onto the bird.
There’s tyrannulets out there somewhere…
A smidgeon of a bird comes into focus but the brakes of sudden confusion prevent you from reaching a positive identification. It looks and acts like a warbler but something’s just not right. As you mentally hesitate at a cerebral fork in the road that leads to its ID, you study the bird in question and realize that the bill isn’t as thin and narrow as that of a warbler. Something about the wings differs from those classic confusing Fall warblers. Ah Ha! They are edged with yellow and then you realize what was lurking in the back of your birding brain from the start- it’s not a warbler at all but a tyrannulet!
Before the short-billed warbler-like thing flits off to another tree, it says, “Peep” (which means I am a Paltry Tyrannulet in flycatcherish) and you almost jump for joy because you avoided the most common tyrannulet-warbler scam in Costa Rica. Off you go looking for more birds and the ability to recognize the Paltry Tyrannulet is strengthened after you identify one Chestnut-sided Warbler after another.
Chestnut-sided Warblers pose as tyrannulets and vice-versa.
Basically, a tyrannulet is a flycatcher that masquerades as a warbler. While the situation gets truly out of control in tyrannulet infested places like the subtropical Andes and southeastern Brazil, there are enough of those miniature flycatchers around here to throw you for a loop on more than one occasion when birding in Costa Rica. In a very general sense, the problem arises for the same reasons that we so love to bird in the neotropics. Birders get a huge kick out of the high diversity but included in that happy bunch of birds are flycatchers that evolved to act like warblers and a falcon that looks kind of like a guan, sounds a bit like a macaw, and acts like a wasp eating jay (yes, the Red-throated Caracara should be featured in a Dr. Seuss story).
In Costa Rica, there are eight species of birds that have tyrannulet in their names but the most important ones to know are the species we see the most. The key to avoid being tricked into thinking that you saw a funny-looking warbler is focusing in the bill and wings (and reminding yourself that Costa Rica has fewer funny warblers than your home patch). Four of the most commonly encountered species are:
- The Paltry Tyrannulet: Laugh at its name now but just wait until you run into one in the field and wonder what the heck you actually saw. Check out the stubby black bill and the yellow edging to the wings. You can run into this species from the humid lowlands all the way up to the high elevation oak forests on Cerro de la Muerte.
Paltry Tyrannulets are common in Costa Rica.
- The Yellow Tyrannulet: Despite yellow being a common shade of the light spectrum in the bird world, this species is aptly named. If you see a warblerish, mostly yellow bird with an eyestripe and distinctive eyebrow flitting around edge habitats in humid areas, it’s probably going to be a Yellow Tyrannulet.
Yellow Tyrannulets are pretty common in most brushy or open habitats in Costa Rica.
- The Southern Beardless Tyrannulet: What an odd name. I mean really, beardless? What bird has a beard? It sounds like some cleanly shaven, miniature king of Alabama. No matter. In the field, you don’t even bother looking for the absence or presence of a beard. Just focus on the shortish bill with a pale base, hint of a crest, and two wing bars and you will hopefully identify this species from Carara on south to Panama and beyond. This is a common bird in most parts of its range but doesn’t seem to occur with its northern cousin (which has much paler and less contrasting plumage).
A molting Southern Beardless Tyrannulet.
Check out the contrast.
- The Northern Beardless Tyrannulet: Here we go again with the beardless thing and once again we can ignore that and focus on the qualities that mean the most. This time, that means pretty much the same things as the Southern B. Tyrannulet but with paler, less contrasting plumage.
Ignore the supposed absence of a tail on this Northern Beardless Tyrannulet- it’s just growing a new one.
As for the more uncommon tyrannulets in Costa Rica, I wish I had photos but because most are canopy dwellers and have an aversion to staying still, they present rather ridiculous challenges for a digiscoper with my rough hewn set-up. I do have a photo of the one that does manage to stop long enough to take its picture though:
Like the other tyrannulets, the Rough-legged, Brown-capped, Yellow-bellied, and Rufous-browed ones are probably easier to identify than the four common species because they have field marks that are easier to see (although it is hard to see much on the Rufous-browed- watch for a skinny thing that looks like a cross between a warbler and gnatcatcher).