On my way to the dermatologist last Thursday I stopped by a nearby Liberia in Alajuela and bought my first all Spanish bird book, Aves de Costa Rica by the now deceased ecologist Alexander Skutch who worked in the southern province of Pérez Zeledón for many years. The book is incomplete of all the many birds here, but it has the Spanish names and descriptions which makes it the only one I know about in español.
I also recently purchased a new English birding field guide that I learned the guides at Rancho Naturalista and others are using because it is more up-to-date than the older English book The Birds of Costa Rica A Field Guide by Garrigues & Dean that has been my main source of info since moving here. The newer book is bigger and includes all of Central America, published this year: Birds of Central America by Valley & Dyer. I’m still getting used to it but like it and it will probably become my new “go-to source” on paper for bird ID here and all of Central America.
It is possible that it could eventually replace the only English birding book for Panama, The Birds of Panama by Angehr and Dean. And the two birding books for Nicaragua that I have: A Guide to the Birds of Nicaragua by Martinez-Sanchez, Chavarria-Durlaux, and Muñoz. It is my only BILINGUAL birding book which I got on my first trip to Nicaragua. Very good! But now on Amazon you can get a newer English-only book Birds of Nicaragua A Field Guide by Chavarría-Duriaux, Hille & Dean.
These could be the last of the paper birding books for Central America with internet and cellphone apps taking over the field with the ability to update daily if needed! eBird and their app Merlin are possibly the best available electronically.
NOTE: If you live in Costa Rica, most of these paper books are cheaper at a local bookstore (Libería) than on Amazon, especially that Spanish book I just got, Aves de Costa Rica.