Rough-legged Tyrannulet (Phyllomyias burmeisteri): Mosquerito frentiblanco; Burmeisterkleintyrann; Tyranneau pattu

Before I pick up on the latest crop of great reports from Aquiares, there’s some unfinished business with Costa Rican flycatchers to attend to. Here then is yet another little flycatcher that I’m sure I’ve overlooked in the past. A post that I wrote in December 2014 on the subject of my confusion with small flycatchers has up until now been the only one in which I have mentioned the Rough-legged Tyrannulet. Even then, the reference was only tangential and at that time I had not really considered that I would ever encounter the species, let alone be able to identify it.

Costa Rica is at the northern limit of this tyrannulet’s range and in this country reports are generally concentrated at middle and upper elevations and away from both coasts. This would seem to indicate that Turrialba’s higher elevations are an ideal location. Nonetheless, Garrigues & Dean’s standard Costa Rican bird guide considers it a rare species throughout its range. This certainly holds true for the immediate Turrialba area, where we have had only three separate eBird reports so far this year. On the Turrialba Volcano slope itself, the Rough-legged Tyrannulet appears to have been found for the very first time in 2018 at Bonilla Arriba by one of the country’s top bird guides, Ernesto Carman. Next, on March 3, 2021, guide Harry Barnard of Rancho Naturalista, accompanied by John and Milena, identified one at a ravine below El Tapojo. John and Milena Beer photographed it a few days later at the same site, where Steven Aguilar Montenegro had managed to relocate it:

The species has since been confirmed (by Mercedes Alpízar of Rancho Naturalista) even higher up on the volcano slope and it is perhaps safe to assume that despite the species’ preference for the forest canopy John will at some point be able to secure more detailed photographs on subsequent visits. We will then try to update.

The relatively large number of eBird reports submitted historically in Costa Rica for the Rough-legged Tyrannulet should perhaps be tempered by the difficulty of identifying it correctly. Its one-inch smaller size (4″) may not render it immediately separable from the fairly common Yellow-olive Flycatcher (Tolmomyias sulphurescens ) or the Greenish Elaenia (Myiopagis viridicata), each of which measures 5″. Thankfully these particular species do not occur much above 1,400-1,500 m, but this is not the case with the very common Mistletoe Tyrannulet (Zimmerius parvus), which measures only 4″ and is found almost country-wide from both coasts up to timberline. Nonetheless, very few reports of the tyrannulet have been been accompanied by detailed observations – descriptions of its piercing call would be very helpful – or by photographs. The yellow wing-bars of the Rough-legged Tyrannulet (not visible in John’s photo above) are a key feature to be noted if you think you may have found one, but both Harry and John note that they are not overly conspicuous and appear to be pale white in colour. They concur with Garrigues & Dean in highlighting also the white forehead above the bill where the superciliaries meet – hence the Spanish name frentiblanco. I myself can hardly wait to return to the Turrialba Volcano slopes that I know so well so that I can add this diminutive flycatcher to my life list.