The Grayish Saltator belongs to the same family as the Black-headed Saltator, which at my parent’s home in Río Frío is much more common. As it name implies, its upperparts are gray, but the underparts are brownish, particularly close to the vent. The throat has a central white stripe, bordered by two black strips. It also shows a white supercilliary which ends right after the eye. The beak is strong as other Saltators. They sometimes come to fruit feeders, but are more wary that most other birds.
The Gray-crowned Yellowthroat is a member of the Warbler family. Its body is generally yellow, with a small black mask and gray crown in the male, features which are much smaller in the female. They have a longer tail and thicker bill than the other Yellowthroat species that occur in the country. The Gray-crowned Yellowthroat is resident and occurs throughout most of the country, while the Masked Yellowthroat is confined to a very small territory in San Vito, and the Olive-crowned Yellowthroat is only found on the caribbean lowlands and mid elevations. The Common Yellowthroat, on the other hand, is a passage migrant, seen from mid October to early April, with some individuals spending the whole winter in the country.
The Western Wood-Pewee is part of the Contopus family, a very difficult family to identify to species level in the field. It is very similar to the Tropical Pewee and the Eastern Wood-Pewee. The best field mark is the bill, were only the base of the lower mandible is orange. This species, unlike the Tropical Pewee, is a passage migrant and will only stay in the country from mid-August to November, and from mid-March to May. In similar fashion to the Eastern Wood-Pewee (and further differentiating from the Tropical), this bird will return to the same perch after a sally, so observing the behavior can help with identification.
The Gray-headed Chachalaca is a relatively big arboreal bird with mostly a brown body and gray head. Their diet consists mainly of fruits. At my parents´ home, up to ten arrive at the feeders where my parents place the papaya. Due to their size, they throw the papaya to the ground while eating, which does not help the toucans when they arrive. They are very loud, particularly when spooked by predators or humans, although not as loud as Brown Jays. They can be seen gliding from tall trees, one after another in rapid succession, relying on the uplift from air currents to avoid expending energy on batting their wings.
The Middle American Rattlesnake is a large, venomous snake. It has a drab color pattern, consisting of dark diamond-shaped blotches on a light brown base coloration. The key differentiator with all other venomous species in Costa Rica is the rattle, which produces a loud, menacing sound when it is vibrated rapidly. Indeed this sound causes fear in most people, as it is associated with the killer nature of these animals. Rattlesnakes however use this sound more as a defensive strategy, trying to scare off potential predators. As long as one is careful not to approach this snake more than it allows, it should be safe to watch them on their habitat.
The Side-striped Palm-Pitviper is a venomous snake, sharing its genus with the Eyelash Palm-Pitviper. The Side-striped is green, which helps to camouflage them in the rain forest, as it mainly has arboreal habits. It has a prehensile tail, which means that it can be coiled around branches that work as an anchor to keep its balance. It is moderate in size, less than 1 meter in length, typically between 60 and 70 centimeters. It has a light-blue postocular stripe. Juveniles are rather drab, having a brown skin.
The Annulated Tree Boa is a large arboreal species that inhabits the Caribbean side of Costa Rica. Unlike other Boa species like the Mesoamerican, one morph of this species are brownish-red in color, which renders them rather conspicuous against the dark green background in the tropical rain forest. Their nocturnal habits and preference for staying high in the trees make them difficult to spot. The color pattern consists of a series of diamond-shaped blotches, which are darker over the dorsum and lighter towards the venter. Some individuals have a cream base color instead of the brownish-red of the specimen shown below.
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; 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 and following the direction of their call, 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 but 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, which lets us peak into the internal structure of a frog. The organs that are visible varies according to the species, with some species showing the intestines and lower organs, while others show the heart and upper structure. In some of them, the bones are also visible inside the legs. Most of these frogs are overall green in coloration, which provides camouflage in the forest environment they live in.
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, and definitely bigger than the Dwarf Glass Frog, which belongs to the same family of frogs. Their skin is mostly green, with yellowish tints in the ventral surfaces of the limbs and in the tips of fingers and toes. Given these colors, it is not surprising that one could be staring directly into one of these on a leaf and still not find it. 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.