Black-striped Sparrow (Arremonops conirostris)

This sparrow has a very peculiar song. It starts with a pair of very high and a lower note, just about a second apart, and the pair is repeated a few times. Then it starts to do a third note, and repeats it many times, in an accelerating fashion, until it stops and becomes silent. Then the song starts again. It is found in the Caribbean lowlands of Costa Rica, in areas of dense vegetation cover. Its underparts are gray, while the upperparts are olive in color. It has two black stripes on its head, one on each side, separated by a gray stripe on the center. It also has a black line that passes through the eyes and almost reaches the neck.