Costa Rica is famous for keeping a high percentage of territory under protection as national parks and reserves. This is wonderful and absolutely laudible but what is often overlooked is the reason why Costa Rica put so much land under protection. Look at satellite imagery of Costa Rica on Google Earth and two things are immediately obvious: (1) a high percentage of the country is deforested, and (2) most of the remaining forest is in mountainous areas. As has so often been the case with protected land in many parts of the world, there wasn’t any push for preservation until alarming areas of the country were bereft of forest. Fortunately, enough people in power realized that the time for protecting biodiversity and watersheds were long overdue, and the national park system kicked into gear.
Fortunately, Costa Rica is also a very mountainous country because steep topography in areas with high precipitation often acts as a natural buffer to logging operations. This is why we still have lots of forest in the mountains, but also why rainforest is a rare commodity in flat, lowland areas. Sadly, such places usually harbor the biggest trees, and the combination of major lumber and ease of access makes them extremely susceptible to logging. This is probably also why Speckled Mourner is so very rare in Costa Rica, why Streak-chested Antpitta is very local, and why Great Potoo is decidely uncommon in the Golfo Dulce lowlands. It seems like all of these species require or prefer flat areas with tall forest, especially the mourner. This is also why it can be tough to gain access to quality, lowland rainforest on the Caribbean slope. Much of that remaining habitat occurs near the border with Nicaragua and at sites in the southeast with other areas of lowland rainforest situated in the Sarapiqui region. Although the best known lowland forests in Sarapiqui are at La Selva, there are other sites that also offer excellent bird and seem to be better for certain species. One of those places is the Tirimbina Biological Reserve, an excellent place to bird whether visiting La Selva or not.
Tirimbina is, in part, an old cacao plantation with a good degree of primary lowland rainforest. Most of the expected species are present except for the two very large eagles (Crested Eagle might still show up but the Harpy is almost certainly gone from Sarapiqui) and a few other species that seem to be susceptible to edge effects and thus require large areas of intact forest (Red-throated Caracara, Black-eared Wood-Quail, and Rufous-vented Ground-Cuckoo). That said, I wouldn’t be too surprised if a wandering caracara showed up on occasion, and perhaps the wood-quail and ground-cuckoo might still be present in very small numbers (or might even come back if we can establish a better corridor with Braulio Carrillo National Park).
Birding at Tirimbina begins right in the parking lot where toucans, chachalacas, Plain-colored Tanager, and other species visit fruiting trees. Those same species along with Rufous Motmot and edge birds can also be seen around the buildings, but the best birding is on the other side of the river. This is where the forest is located and this is the place to see tinamous, antbirds, Red-capped Manakin, and species of the tall forest. Getting there requires a walk across the river bridge (open from 7 to 5, even guests have to check in with reception), and if you are visiting for a day, stopping by the reception to purchase a day pass ($17). The lack of nocturnal access to the best forest is disappointing but that’s the way the birding ball bounces.
From the bridge, scan the river for Fasciated Tiger-Heron and Sunbittern. Agami Heron is also seen now and then as it stalk smaller side channels. The bridge is also a good place to scan the canopy for perched raptors and Snowy Cotinga (not uncommon).
Once inside the forest, careful birding along any of the trails can result in Great Tinamou, and literally hundreds of possibilities.
We had three Great Tinamous at an antswarm. They were very tame!
Speaking of antswarms, we ran into one last month and had perfect looks at Ocellated Antbirds along with Bicolored and Spotted Antbirds, and Northern Barred Woodcreeper. Although we didn’t see anything else with the swarm, it could certainly attract many other species including motmots, forest-falcons, and who knows what else.
One of the Ocellated Antbirds.
The understory is also good for mixed flocks of insectivores. These birds tend to be quiet and unobtrusive. Listen for the sharp call of Checker-throated Antwren, and watch for White-flanked Antwren (pretty uncommon in Costa Rica), Streak-crowned Antvireo, Sulphur-rumped Flycatcher, and other species.
Female White-flanked Antwren.
You also need to watch for canopy flocks. These can host some exciting species, the star of the Tirimbina show being White-fronted Nunbird. This formerly common species has become rare in much of the Caribbean slope because so much of its required lowland primary rainforest habitat has been cut down. The canopy flock might also have Black-striped and Cocoa Woodcreepers, Green Shrike-Vireo, White-shouldered Tanagers, oropendolas, and maybe even Rufous and Broad-billed Motmots. From August to February, such flocks can also have Bare-necked Umbrellabird (!).
The canopy also hosts some lowland specialty flycatchers best seen from a hanging bridge that acts as an erstwhile canopy tower. Those target flycatchers are Black-capped Pygmy-Tyrant, Yellow-margined Flycatcher, and Brown-capped Tyrannulet. Continuing on, keep an eye out for fruiting trees that could attract other birds, and in creek beds and seeps with a thick understory, listen for the low, two-noted whistle of Slaty-breasted Tinamou. This tough species is much less common than the Great, and Tirimbina is one of a few reliable sites for it.
As with any lowland rainforest site with good forest, of course many other species are also possible. Just keep checking the same trails because the more you look, the more you see. This site also works well in combination with an early morning birding tour at La Selva. Do that, and bird Tirimbina for four days to a week and you have a fair chance of getting most targets, and hitting 300 species (especially if you hire an experienced guide). Who knows, maybe you will even find that Speckled Mourner? I know two people who found one at Tirimbina a few years ago.