These are euphonias of course, almost certainly Scrub Euphonias. Scrub Euphonias are common birds around Laguna de Apoyo. I hear ‘em all the time. When I took the photo, I just thought it was a great moment, an adult male feeding what I assumed was a young bird, or possibly a female.
Later on, looking at this photo on my computer, I started thinking. Wow, I thought, there’s an awful lot of yellow on the crown of that male euphonia… Scrub Euphonias have less yellow there than other, similar euphonias. The yellow on this bird extends to just a little beyond the eye, while the Scrub Euphonias I know – and the ones depicted in the guides – all have a yellow crown patch that ends just before the eye.
So I started wondering, which other euphonias are there to consider?
Well, there’s Spot-crowned Euphonia. It has a bit more yellow on the crown than Scrub – the spots are only visible from certain angles.
Here’s a photo of the same bird showing the crown really well. There are no crown spots visible, so I think we can rule out Spot-crowned. The female Spot-crowned, incidentally, has buff underparts and a buff crown spot, which the female/juvenile type bird in our photo doesn’t have. (I don’t know if a juvenile Spot-crowned would have the buffy coloration.) Spot-crowned is found in neighboring country Costa Rica, not in Nicaragua.
Orange-bellied Euphonia (which incidentally has a yellow belly) is from even further afield – South America – with records from Panama. It has more yellow on the crown, in fact a bit more than our bird. Altogether an even more unlikely candidate, one we probably don’t need to consider.
A bird that is found in Nicaragua is Yellow-crowned Euphonia. It has a lot more yellow on the crown than Scrub. As far the yellow on the crown is concerned, the bird in the photo is almost intermediate between Scrub and Yellow-crowned.
The birds I photographed are probably just Scrub Euphonias. There may be some regional variation in the amount of yellow on the crown that I wasn’t previously aware of. It has a fairly large range, all the way from Mexico to western Costa Rica. Two groups are known; one with a yellow vent and one with a white vent. This is the yellow-vented variety.
All in all, these birds provided an opportunity for me to study yellow euphonias with black throats a little bit more.
Postscript: Dana Gardner's illustration of the male Scrub Euphonia in the excellent Stiles & Skutch Guide to the Birds of Costa Rica actually shows exactly the same amount of yellow on the crown as the bird in my photos. This confirms the ID. Now I'm even more inclined to think that there is at least some clinal variation in the amount of yellow on the head, from less yellow on northern birds to more yellow on southern birds.