The Mexican Tree Frog is among Costa Rica’s biggest frogs. It is somewhat similar in appearance to the Masked Tree Frog, however the Mexican is bigger and its overall color is brown instead of green, and does not show such a definite dark brown patch behind the eye. The eyes are very similar between both species. It does occur in the Guanacaste province, from which the Masked is absent, however it is not found on the Pacific south from the Tarcoles river. They are nocturnal and arboreal like most tree frogs.
The Dwarf Glass Frog is the smallest Glass Frog to be seen in Costa Rica, roughly similar in size to a Strawberry Poison Dart Frog, but given its green dorsal skin it is more difficult to spot, specially if they stay motionless on a green leaf; increasing the probabilities of seeing one is the fact that they call from the upper side of leafs, so putting enough attention one might discover an individual. Their eyes are more forward facing than the Dusty Glass Frog, which is the other member of the Teratohyla genus and is a lot larger, also differentiated by the lack of any spots on the Dwarf. An important reproductive characteristic of this species is that the egg clutches are left hanging from the underside of leafs, above a stream so that tadpoles can easily drop to a certain source of water.
Glass Frogs are fascinating, given their transparent ventral skin. This species is called Dusty given how the dorsal skin is covered in very small white spots. They are intermediate between the sizes of Strawberry and Green and Black Poison Dart Frogs. Their skin is mostly green, with yellowish tints in the ventral surfaces of the limbs and in the tips of fingers and toes. The eyes are very large, located at each side of the head, enabling the frog to spot predators from both sides; the pupil is horizontally eliptical, while the iris is covered with an intricate pattern of blue and gray.
The Hourglass Tree Frog receives its name from the dark brown mark on its back, which resembles an hourglass due to its shape. Overall, it is colored orange and brown, with small light spots on darker areas and small dark spots on the lighter zones. Some individuals are rather pattern less and look entirely orange. It is common and widespread in both caribbean and pacific lowlands. This species is arboreal and nocturnal, and can be found in disturbed areas, including gardens close to people’s homes. It is not likely to be confused with any other frog species that inhabit Costa Rica, although the other two species in the Dendropsophus genus have a similar orange color, but without the intricate patterns of the Hourglass.
There are three Long-snouted Tree Frog species in Costa Rica, with the Boulenger’s and Olive being both widespread and common accross wet lowlands in the country, and the Dry Forest species being common in the northwest region (Guanacaste). The Boulenger’s is mostly light brown, including the iris, with small patches of green and darker brown that provides better camouflage. It is colloquially known as “Rana Lagarto” (crocodile frog) in Costa Rica due to its unusually long snout.
It is arboreal and nocturnal, and males frequently call with their body upside-down during the wet season. To help hold this position, the innermost finger can be rotated up to 90 degrees, essentially pointing upwards, which provides a better grip on smooth surfaces like tree branches and trunks. The skin is granular, which might put off some people that call that appearance gross. Yet amphibians have a very important role in wet ecosystems, as some of the insect prey they consume might develop into plagues if unchecked. Most amphibian species have been battling with declining populations, and protecting them from extinction is one of our biggest challenges.
The Common Ground-Dove is very similar to related species Ruddy and Plain-breasted Ground-Doves, however the Common is lighter in coloration, with a pink bill that is diagnostic; it also shows a scaled pattern in the throat and neck, which is missing from the other ground doves. Also similar to these species is the Inca Dove, which even behaves similarly as it forages most of the time on the ground, however the scaled appearance in the whole body should preclude any confusion. The male is ligher than the female, which looks grayish. All ground doves feature dark spots in the tips of primaries and secondaries, which look like a curved line when the wings are closed, although the Common’s should area spots are more numerous and do not form a line.
There are six species of Antshrikes that occur in Costa Rica, some more elusive than others, but all having a common theme: Their songs is heard more often than they are seen. All of them sing using a pattern of repeating notes that build more speed slowly, abruptly ending in a single note that usually is different from all others. The song of the Black-crowned Antshrike is very similar in pitch to the Barred Antshrike’s, so it is easy to confuse them. The Black-crowned is bigger and does not have the bold markings that the Barred has, only displaying small white dots and stripes on the wings, along a black crown which is difficult to see, given that they are usually perched higher than eye level inside the dark forest.
The Heliomaster genus contains four species, two of which occur in Costa Rica, including the Long-billed Starthroat that can be spotted in the Caribbean and northern lowlands, as well as in the south Pacific. It also includes the Plain-capped Starthroat, which is mostly seen in the north Pacific, central valley and some valleys in the south Pacific.
Both Starthroats have longer than average bills which are straight, although both species have similar bills. The main difference between the Long-billed and Plain-capped is that the former displays a colorful blue-green forecrown, while the latter lacks that crown. To aid in identification, it can be noted that the Long-billed has a postocular spot, while the Plain-capped has a postocular strip. Other than those two specific traits, the two species are very similar, with olive upperparts and gray to white underparts, and a magenta throat that is iridescent. The tips of the tail feathers are white, which can be seen the most dramatically during flight.
Purple Gallinules are some of the most brightly colored birds that you can see walking in Costa Rica. Indeed while they can also fly, they more commonly wade in shallow waters and in dense grass plains, looking for prey. I have seen them in Palo Verde in big numbers, and spotted individuals in Rio Frio, where they join chickens and forage in the backyards of houses; indeed I was able to see two adults rearing four young hatchlings, which were still covered in black fluffy hairs, getting along with the chickens just fine. The underside and head is entirely purple with a metallic look, showing a small light blue patch on the forehead. The beak is mostly bright red, with a yellow tip. The upperparts show blue to olive green hues, particularly on the wings. The yellow legs are long, letting them to wade in shallow edges of lagoons without having to swim.
The Black-and-yellow Silky-flycatcher is one of the four species in a unique family around the world, with the Long-tailed Silky-flycatcher being the only other species to be seen in Costa Rica. The male shows a combination of yellow rump, chest and undersides, with gray belly and vent; its throat and head it black, as well as it tail and wings. The Female has a gray throat with a black cap, olive chest, wings and tail. Their shape is similar to other Costa Rica thrushes, as they look rather plump when compared with the Long-tailed. Although Flycatchers by name, they prefer to eat fruits, specializing in berries that are abundant in the highlands; indeed their range is restricted to Guanacaste, Tilaran, Central and Talamanca Cordilleras. They are endemic to Costa Rica and western Panama, thanks to the fact that the Talamanca Cordillera stretches out into Panama.