The Masked Tree Frog is a nocturnal, arboreal species that can be found on the lowlands and foothills of both the pacific and caribbean sides of Costa Rica, although it does not occur on the dry plains of Guanacaste. Its color is variable, however the dark brown patch behind the eye is unmistakable. Their color ranges from entirely tan to entirely green, with intermediate, contrasty patterns in between. When most of their body is tan, it can look very similar to the Cross-banded Tree Frog, however the Cross-banded never has a mask. Their vocal sacs are bilobed, which essentially means that it looks like two vocal sacs, one at each side of the throat.
I have an story of a time I visited Mirador El Pizote, in Boca Tapada, San Carlos. One of these frogs had entered the cabin where I stayed, possibly during the night. I was going for a bath and found the frog resting on the bathroom. After trying a few pictures (that did not work out very well), I tried to grab it to put it outside, but it jumped rapidly and dissappeared. Since I could not follow its movement, I was never sure whether it went outside or stayed inside.
The Spectacled Parrotlet was one of the species that we did not expect to see during our trip, however I was lucky enough to observe a pair of them perched on a bamboo fence in Cali, when visiting the CRARSI. The female is really similar to the Orange-chinned Parrolet, except for not having the orange chin that defines that species. The male has a darker green coloration on the body overall, and sports a turquoise mask along with blue plumage under the wing. They are the smallest parrotlet species that exists in the world.
The Flowerpiercers are small birds in the Tanager family that have the upper tip of the bill curved down, allowing them to pierce flowers from the base and drink their nectar, hence their name. Their very short bill do not allow them to drink nectar like a hummingbird does, by inserting the bill into the flower, so they do not pollinate flowers. Instead, they used their bill to open up a hole at the bottom of the flower, and drink the nectar that dips from it. Both the Masked and the Black Flowerpiercer have a similar shape and size, however their colors are pretty different. The black mask with bright red eye of this species is unmistakable.