In 2016, I spent some crazy time in Bayahibe, at the southeastern tip of the Dominican Republic. There is quite an impressive country park near the place I used to stay, El Parque Nacional del Este. Entry is cheap (about $2 maximum) and the whole natural reserve is considered as the jewel of southeastern coast.
The most amazing part of the reserve is a subtropical rainforest. You can cross through it using a trail called El Sendero del Padre Nuestro. The trail leads you to underground caves where the oldest inhabitants of this part of the island used to live in. If you fancy a birding expedition during your holidays in Bayahibe, I highly recommend you to visit El Parque Nacional del Este. You will see hundreds species of flowers as well as numerous birds uncluding very special ones such as the red-footed boobie and the brown pelican!