It is a very popular creature throughout the island and enlivens the evenings with its timid ko-kee from which it get its name. The coquies begin to sing when the sun goes down at dusk, singing all night long until dawn. The male coquí sings - not the female. You can find the coquí nearly everywhere, from the margins of the forests where the areas receive large amounts of moisture, in highlands, lowlands, dry and arid places, even in caves depending on the species.

http://welcome.topuertorico.org/audio/C01.wav
At the very beginning I wonder it's the voice from birds, so
brilliant! After several days I realized it's frogs.

The best frogs' night song in the world, I will say.

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Coquis reproduce year-round in Puerto Rico, but breeding activity is concentrated in the wet season. This species utilizes internal fertilization and like other eleutherodactylids, the fertilized eggs undergo direct development, rather than passing through a free-living larval (tadpole) stage, which means the parents don't have to lay their eggs on water, as it happens with other amphibians. The "tadpole" stage occurs entirely within a terrestrial egg, rather than as a free-living larval stage, and adult features form directly, sometimes bypassing the stages normally present in tadpole ontogeny (Hung and Elinson 1996, Hanken et al. 1997). Thus, a tiny but fully functional froglet hatches directly from the egg. Coquis deposit 4-6 clutches of about 28 eggs each (range 16-41) per year, with a development period of 17-26 days. Males guard the eggs to keep them from drying out and remain in the nest for a few days after they emerge.

Special? Everything is special in some way, and I know some
snakes can give birth to little snakes directly.

http://welcome.topuertorico.org/coqui.shtml
Sorry I cannot read chinese here ...