Yellow Tyrannulet (Capsiempis flaveola): Mosquerito amarillo; Tyranneau flavéole; Zitronentyrann
The Yellow Tyrannulet is a lowland flycatcher species that is now seen regularly at Angostura. It measures a mere 4″ from head to tail, which makes it a very small bird. It does draw attention to itself because it frequently repeats its call, best described as a sputter. It is not found at elevations much above 900 metres, which excludes it from my own location on the Turrialba Volcano slope. This makes it necessary to descend to the Caribbean foothills of Turrialba if we want to find it. It is still rather uncommon but has been reported lately with increasing frequency, almost always close to the Angostura Dam.
Identification is not too difficult even though many other flycatchers of the more than 50 found in Costa Rica share the all-yellow underparts. Its small size, long tail and distinctive call distinguish it from most other contenders, including other tiny tyrannulets and spadebills, most of which are not found in the Turrialba area at all.
A possible source of confusion might just be the Rough-legged Tyrannulet (Phyllomyias burmeisteri). This similarly sized flycatcher does have a long tail and mostly yellow underparts, albeit with streaking. However, it is a rare species of middle and higher elevations with few reported sightings in the Turrialba area. These are almost always from elevations a little higher than Turrialba, for example near the Rancho Naturalista. The photos below are from very high up the volcano slope:
The bird species that is perhaps the most similar to the Yellow Tyrannulet is the Yellow-winged Vireo (Vireo carmioli), which is found in very different environment, usually quite high on the mountain slope, rather like the Rough-legged Tyrannulet. This, however, is a common vireo species that is endemic to Costa Rica and western Panama. Nevertheless it is rarely, if ever, found below an elevation of 1500 metres. The following photo was taken at El Tapojo on the Turrialba Volcano slope at almost the same exact location as the preceding Rough-legged Tyrannulet.
Yes, it is difficult sorting out Costa Rica’s myriad flycatchers, but it’s also a very rewarding exercise performed always in beautiful surroundings.