Thursday, April 2, 2015

A Full Day at Costa Rica's La Selva

Our last four days in Costa Rica went by in a flash yet at the same time seemed to be as full of experiences and sightings as the first nine days. On these days we were on the more lush Caribbean slope, first in the foothills of the Tilarán range, which are something of a transition zone from the Central range and the Guanacaste range of volcanic peaks. We spent a full morning near the Arenal Observatory Lodge, and our pre-breakfast walk was surprisingly successful (being in a patch of secondary forest adjacent to over-manicured gardens), with a family group of Song Wrens (the male singing his fascinating song that alternates so rapidly between short, pure whistled tones at varied pitches and harsh chuckling phrases that it seems two birds must be singing at once), a Black-headed Nightingale-Thrush, and a pair of Spotted Antbirds being the main highlights. The porterweed in the gardens attracted several hummingbirds including our only Black-crested Coquette, a female. We also stopped to take pictures of this flowering bush in the dark understory, and my guess as to the caper family (with its brush of many stamens) led me to the name Capparidastrum discolor.

On our late morning walk, the only bird photo I managed was of this Great Curassow in the crown of a tall tree, where it had been singing its nearly subsonic humming growl, making it very hard to locate.

We also had our best views of a beautiful male Scarlet-thighed Dacnis in a small fruiting tree just off the trail (made especially beautiful by its direct comparison to the utterly drab Ochre-bellied Flycatcher also feeding from the fruits), and a pair of Buff-rumped Warblers countersang, probably reaffirming their territorial boundaries right along the trail. So wrapped up in his business, one came with in a few feet of our group several times, and the ringing song at that close range was almost painfully loud. Sometimes I’ve had to resort to using playback to bring one of these birds closer for even brief views, but this was by far a more satisfying experience.

We had the next full day at La Selva, the famous research station of the Organization for Tropical Studies. While it was bustling with students and a few independent researchers, it’s also a magnet for groups of ecotourists, especially birders, who pay an entrance fee as well as for a local guide, the help from whom I’ve never been disappointed in. We arrived before La Selva officially opened at 7:00, which fortunately put us at the right spot at the right time to see seven gorgeous male Snowy Cotingas gathering in three trees on either side of the entrance drive, posturing, giving short display flights, and displacing each other on branches. About the size of an American Robin but chunkier and with a shorter tail, this oddly silent bird (especially odd considering that some members of the cotinga family are among the loudest of all birds) is special for being one of very few all-white passerines in the world.

This visit we were accompanied by Joel, a very good birder who has worked here for many years as a guide and a field biotech for researchers. He asked me where we had been in Costa Rica and which birds we hadn’t seen yet, and when I mentioned Rufous Motmot, any puffbirds, tinamous, and quail-doves, he chose to take us down the STR, a wide, paved path with good views of the understory as well as lower areas of the canopy. But we didn’t get far, as the bird activity near the bridge was high. Collared Aracaris were coming into the fruiting bushes just a couple feet away, impatiently hoping we’d move on, while a large group of Crested Guans walked nonchalantly nearby and our first Crowned Woodnymph and Black-cheeked Woodpecker foraged in another tree. These two Crested Guans were just a couple trees farther along, possibly part of a big extended family.

The Queen Mary Bromeliads, Aechmea mariae-reginae, were in full bloom this year, mostly high in the trees, but this one was below eye level from the vantage point of the foot bridge crossing the Sarapiqui River.

We moved on down the trail, stopping to marvel at leafcutter ants, millipedes, and the occasional bird. Not far down the trail, Joel stopped to show us large holes dug into the dirt banks on either side of the trail where he thought Rufous Motmots might be currently nesting. Sure enough, a few steps farther, he spotted this giant of motmots perched motionless in the midstory.

Chrysomelidae is a huge family called leaf beetles, and the subgroup known as tortoise beetles are particularly attractive. This one is Ischnocodia annulus and has been called the Target Tortoise Beetle.

If it weren’t for Joel, we might have walked right past this Black-capped Pygmy-Tyrant. I had heard one in the canopy earlier, but ignored it, as seeing one of the world’s smallest passerines is almost impossible when they are singing from the tallest trees as they usually do. But this one was bringing food to a nest, a hanging pouch dangling from the petiole and hidden behind the blade of a large philodendron leaf just 10 feet above the trail.

Belonging to Costaceae, one of the families in the ginger order (and strangely unknown in the temperate zone even as a house plant or ornamental), this is Costus malortieanus.

Another bird I had mentioned to Joel as one missing from our list, Black-throated Trogon appeared in spades.

Recognizing the cauliflorous fruits on this vine as a member of the family Sapindaceae (looks reminiscent of ackee, with a bright aril meant to attract dispersers) helped me find the name Paullinia fasciculata on the Digital Flora of La Selva website.

We then took a narrower trail back for lunch, hoping for more understory birds. Joel was pointing out an active nest of a Lesser Swallow-tailed Swift on a huge tree trunk overhead (which I failed to photograph for some reason, except for maybe because it paled in comparison to the one I found with Jake, Paul, and Steve in northern Peru last May) when one of the tour participants noticed this small Eyelash Pit Viper just below (my) eye level an arm’s reach from the trail. It is indeed venomous, apparently with a very potent venom, but it is not an aggressive species, and strikes seem to be very rare considering how common it is and how easy it is to overlook. It’s possible that the species is reluctant to strike in defense unless really bothered –  every one I have ever seen has remained utterly motionless and probably has no reason to believe it’s visible. But we were warned to remain at least as far as most of its body length. It uses only the very last loop of its tail around the branch as an anchor and can strike at a distance of a the remainder of its body length.

This is a refuse pile of Atta colombica, the Surface-dump Leafcutter Ant.

Rubyspot damselflies of at least two species were here and there along the trail, hunting from the tips of leaves at eye level. La Selva has several species, and I’m guessing that this one is a male Hetaerina titia. Joel said that expert odonatologist Bill Haber had just been here, updating the La Selva species list, even discovering a new species of damselfly in the process.

After lunch back at the main center for lunch, we took a short break when I shined my headlamp into a small hole in a dirt bank right by the gift shop. In it was this Yellow-spotted Night-Lizard, Lepidophyma flavomaculatum, which retreated deeper in before I could get a photo better illuminated by my flash.

This vine in the family Marcgraviaceae is Souroubea gilgii, normally attractive to honeycreepers and hummingbirds, but it remained bird free and merely beautiful while we were watching.

Also during our break I found this Passiflora auriculata passionflower, which surprised me by being wonderfully fragrant, like chocolate and strawberries. Most passionflowers have no smell, and some are even foul smelling.

I was amazed to see this female Fasciated Antshrike and her mate at eye level in the bushes by the gift shop, so far from the canopy where I’ve spent many neck-breaking minutes trying to bring one in with playback. Like a few other birds we saw here, they were on a foray out of their usual element to collect nesting material.

We took another walk back in the forest, finding a pair of Broad-billed Motmots.

This Gray-waisted Skimmer, Cannaphila insularis, was perching in low vegetation right next to the trail.

Joel took us to a tented leaf where these amazing Honduran White Bats were roosting. They had been using it for about two weeks by now, and we were among hundreds of people who had seen them, one by one. The leaf was only about four feet off the ground, well visible about ten yards from the main trail, but a narrow path had been worn to it where one could carefully walk without unduly shaking the surrounding vegetation, kneel and look up under the leaf (unfortunately placed directly below a very bright hole in the distant canopy, making a good photo impossible). The tiny 1 ½-inch bats had created the tent by biting along either side of the central vein of the leaf. Many species do this, but I had seen this one just one previous time,  and I think it was my first visit to La Selva in March 1998.

One last photo from La Selva is of this spider lily relative, Crinum erubescens, growing along a narrow stream in the deep forest understory and visible from a short foot bridge.

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