Sea Turtles, Volunteers and Visitors

Sea Turtle Conservation Program: October Update

We’ve completed another month of the sea turtle conservation program on the Osa Peninsula, Costa Rica and we’re getting close to the end of the nesting season. After 4 months of tireless work by our field coordinators, field assistants and volunteers, we have registered a total of 1233 sea turtle nests, between Piro and Carate (Fig. 1). As I mentioned earlier, for logistical reasons, we cannot gather daily information from all beaches and visits to Rio Oro beach have been very limited, so this number of sea turtle nests should be considered a minimum; i.e., the actual number of sea turtle nests on these beaches is higher than reported here.

Figure 1. Total nests registered, according to month, beach and species. CM: Chelonia mydas agassizii, DC: Demochelys coriacea, EL: Eretmochelys imbricata, LO: Lepidochelys olivacea

Of these 1233 recorded nests, we know that at least 242 (20%) were predated. Of predated nests, 43% were by humans, while the remaining 57% were predated by dogs, pigs, crabs and other animals. We can reasonably estimate that approximately 10,600 eggs have been illegally removed between Piro and Carate for human consumption (assuming that each nest had 100 eggs and they were all taken).

If we focus on the Olive Ridley sea turtles (Lepidochelys olivacea), the most common sea turtle species on the Osa Peninsula, not taking into account the Rio Oro data, as the data that we have doesn’t appear to be representative of the real situation, we can see that during the 2010 season, Carate beach is where we find the greatest amount of illegal harvesting of eggs (Fig 2). Throughout the season, more than 50% of reported predation is caused by humans, a situation that hasn’t occurred on Piro and Pejeperro beaches.

Figure 2. Percentage of Olive Ridley sea turtle nests predated by humans and other animals according to month and beach.

Remember that you can help us save sea turtles that visit the southern part of the Osa Peninsula in several ways: 1) tell others about our project and the importance of protecting sea turtles, 2) by volunteering with sea turtles or 3) by making a donation to support our sea turtle program or the other conservation work that Friends of the Osa does on the Osa Peninsula.

Birds

Featured Bird: Red-legged Honeycreeper

Red-legged Honeycreeper

The Red-legged Honeycreeper (Cyanerpes cyaneus) can be found here on the Osa Peninsula and can often be seen wandering through humid forest canopies and open areas with its other Honeycreeper relatives the Green Honeycreeper (Chlorophanes spiza), the Shining Honeycreeper (Cyanerpes lucidus) and the Blue Dacnis (Dacnis cayana).  For those novice birders trying to get their bird bearings here in the tropics, one can at first glance mistake the Blue Dacnis or the Shining Honeycreeper for a Red-legged Honeycreeper.  At least I did the first few weeks, but all you have to do is look for the distinctive red legs or the long decurved bill if you’re not yet Dacnis proficient.  Also, one surprise that the Red-legged Honeycreeper has for any onlooker is the bright yellow color of the underneath portion of the wing.

Honeycreepers used to be classified in a separate family with the Bananaquit and flowerpiercers, but are now part of the Tanager family which may seem a bit odd considering their nectar feeding habits and bill morphology.  Any commentaries on why they were lumped with tanagers are welcome here by the way.  But whether you’re a lumper or a splitter, tanagers display more colors and color patterns than any other tropical American bird and Honeycreepers definitely fit the bill.  If you’re not sure what I mean find images of Golden-hooded Tanagers and Bay-headed Tanagers and you will see what I’m saying!

Female Red-legged Honeycreeper

Red-legged Honeycreepers extract nectar from the flowers of Inga, Calliandra and other legume plants.  They also eat small insects, arillate seeds and many other fruits in fairly open edgy areas.  We have seen them moving in mixed-species flocks high up in primary and secondary closed canopy forests as well as right in the gardens of the Osa Biodiversity Center at Friends of the Osa during our early morning avian monitoring point counts.

This species is an open cup nester building a nest of fine rootlets and grass raising two young between February and June.  Pairs are monogamous and both take care of incubation and nesting duties.  Oh, and in case you’re curious Red-legged Honeycreepers weigh about 13.5 grams, about half the size of a House Sparrow.

Visit Photographs by Bob Levy for more beautiful birds of Costa Rica.

Birds

Featured Bird: Turquoise Cotinga

Male Turquoise Cotinga. Photo by Ulises Quintero

This week as promised I am bringing you the Turquoise Cotinga (Cotinga ridgwayi).  This is definitely one of those species of bird that makes you go “WOW” when you see it.  This is also one of Costa Rica’s most sensitive species to loss of forest habitat.  BirdLife International has this Cotinga species listed as Vulnerable which puts it one step away from be considered Endangered.  It is a regional endemic only found on the Pacific slope of central and southern Costa Rica and western Panama.  Its population is estimated to be between 2,500 – 10,000 birds and declining.

So why the decline?  As with many species, the Turquoise Cotinga is faced with deforestation and severe habitat fragmentation.  This coupled with an already naturally small range makes it difficult for the Cotinga population to remain stable.  This is also true for its closest relative the Yellow-billed Cotinga also found here on the Osa Peninsula whose population is estimated to be much smaller between 250 – 1,000 birds (more on this species in the weeks to come!).

Because of the Turquoise Cotinga’s conservation concern and its rarity, it is a special occasion when we see one.  Now you must know there are certain areas on the Osa Peninsula where this bird is quite common such as Carate and Corcovado National Park and folks flock to these areas to see them.  Since we at Friends of the Osa are in the middle of our seasonal avian monitoring we have had the distinct pleasure to have encountered several Turquoise Cotingas in the last two weeks within our monitoring points and just up the road from the Greg Gund Conservation Center on Cerro Osa.  It is possible that Turquoise Cotingas are more common than once thought on Friends of the Osa property especially outside of the breeding season when they are seasonally migrating in search of food resources.

This passerine species is found mainly in the canopy of humid rainforest and secondary growth and can also be seen along forest edges and in tall trees within shade grown coffee plantations.  They will wander throughout the canopy of wet forests and are known to rest on high exposed perches.  They consume the fruits of fig trees, Cecropia and parasitic mistletoe Psittacanthus and will go down low to gather pokeweed berries Phytolacca in clearings on occasion.  In case you were wondering it weighs in at about 50 grams, just under the size of a Red-winged Blackbird.

The males and females apparently do not form pair bonds.  The males gather in group display leks to attract females.  The female then builds the nest and rears the two young all on her own.  Nesting takes place between January and May.

Conservation measures are to investigate current distribution and discourage the conversion of shade coffee to full sun grown coffee.  Unfortunately very little information is available on the behavioral ecology of this species so the more we learn the more we will bring to you.

Birds

Featured Bird: Pale-billed Woodpecker

Pale-billed Woodpecker Male. Photograph by Alan Dahl

Of the eight woodpecker species that are found on the Osa Peninsula, the Pale-billed Woodpecker (Campephilus guatemalensis) is the largest with a length of 35 cm (14 inches) rivaling only the superficially similar, and range overlapping Lineated Woodpecker (Dryocopus lineatus).  In fact, the Pale-billed Woodpecker is most closely related to the extremely elusive north temperate species the Ivory-billed Woodpecker, both belonging to the same genus, Campephilus.  This species ranges from southern Mexico to Western Panama.

The Pale-billed is distinguished from the Lineated by its fully red head.  Only the female, pictured here, has a black center crown, neck and throat while the male’s head is completely red.  When their bright red crest stands up on end they look like the punk hoodlums of the bird world.

These birds are actually quite common here on the Osa and can be found right here at the Osa Biodiversity Center anywhere between the Greg Gund Conservation Center and Piro Research Center.  There is a pair that is excavating a nest right now in the month of September in our NRDC forest restoration plot located approximately 6 meters up in a snag.

Pale-billed Woodpecker Female. Photograph by Gianfranco Gomez

The nesting period typically ranges from August to December.  Pale-billed Woodpeckers excavate their own nests, but are sometimes taken over by Araçaris while under construction.  Both parents incubate the two eggs typically layed and also care for their young.  They roost in large cavities similar to those used for nests and can use the same cavity for roosting for several months.

They commonly eat the large larvae of wood boring beetles excavated from the trunks and limbs of large trees and dead and decaying wood.  When not eating beetle larvae they have been known to take fruit from Melastome trees.

Sounds include the vocal “bleating” sound and the non-vocal drumming “double-rap” similar to that of other Campephilus species such as the Ivory-billed Woodpecker.  The NRDC pair is in the habit at the moment of counter-rapping with its nearest neighbor who is only about 100 meters away.

We would like to thank Alan Dahl from Focused on Nature photography and Gianfranco Gomez from the Drake Bay Rainforest Chalet for allowing us to show off their amazing photographs of the Pale-billed Woodpecker.

Miscellaneous, Science and Research

In Search of Amphibians on the Osa Peninsula

In 2008, in order to determine the distribution and abundance of leaf litter amphibian species, I began a monitoring program around the Piro Research Center along with Federico Bolaños and Gerardo Chaves, herpetologists from the University of Costa Rica. In 2010, with the support of the Mohamed bin Zayed Species Conservation Fund (MBZ), I expanded this project to Los Charcos and Petosa, a private property owned by Bert Kerstetter, an important supporter of Friends of the Osa.

The information generated by this project was included in the latest update workshop of the conservation status of amphibians in Costa Rica for the IUCN Red List, held in San Jose in July this year. The workshop was organized by the University of Costa Rica’s School of Biology and the Conservation Breeding Specialist Group (CBSG) of the Species Survival Commission of the IUCN. The workshop summary will soon be published by the organizers, and we’ll share that report through the blog.

Dermophis occidentalis

As part of this project, and with some good luck, we’ve observed many interesting species of amphibians.  One species in particular which has attracted the most attention is the caecilian seen in this photo.

Caecilians are a group of amphibians that has invaded the underground environment, so that their bodies are elongated, they have no limbs and their eyes are vestigial – all characteristics that allow them to squirm through their subterranean tunnels. Because of their penchant for the underground, these animals are rarely seen, and therefore, little is known about them.

According to the latest review of this group in the Osa Peninsula, there are three species of caecilians, one of these endemic (Oscaecilia osae), which has been reported only twice in Corcovado National Park.

The species that we have been observing, Dermophis occidentali, has been found at both the Piro Research Center, and the Greg Gund Conservation Center (GGCC).  The individual in the photo was found at the GGCC by Kory Kramer, in one of the buildings. This was in early July, when the onset of the rains saturates the ground forcing caecilians to surface.  If you’re lucky, you’ll see one. On this occasion, all Friends of the Osa staff were gathered for an activity so that everyone had the opportunity to observe this rare species.

Birds

Featured Bird: Chestnut-backed Antbird

Chestnut-backed Antbird. Photo by Alan Dahl

Chestnut-backed Antbirds (Myrmeciza exsul) are common residents of the Osa Peninsula and one of the most abundant species found here.  It is difficult to walk outside here at Friends of the Osa’s Osa Biodiversity Center and not hear two or three individuals counter-singing.  Often times when the rest of the forest has become fairly quiet you can always count on a Chestnut-backed Antbird to let you know that all is as it should be.

The signature look of three species of Antbird found on the Osa Peninsula of Costa Rica is the blue orbital skin (the skin surrounding the eye).  The Chestnut-backed Antbird is one of these species and is distinguished from the others by its slate colored head and chestnut back.  The other antbird that you are likely to see here with the blue orbital skin is the Bicolored Antbird, but it is distinguished by its white neck and belly.

As you can tell by the name, Chestnut-backed Antbirds follow army ant swarms; however, they only do this occasionally and are not considered obligate, or professional, army ant followers.  They are strongly associated with the dark undergrowth of wet tropical forests within dense vegetation especially near overgrown treefalls or dense thickets.  They often join mixed species flocks but won’t necessarily move along the forest with the flock, but will rather join them while ant swarms are moving through the dense thickets in which the Chestnut-backed Antbirds are found.  Once the army ant swarm or the mixed species flock is gone, they will remain in the undergrowth found in their territory.  Many tropical birds follow army ant swarms to pick up insects flushed by the ants, not to eat the ants themselves.  Chestnut-backed Antbirds mainly hop along very low lying perches or along the ground and peck their prey, which mainly consists of insects and spiders from the ground or near the ground vegetation.

Chestnut-backed Antbird. Photo by Gianfranco Gomez

They are territorial throughout the entire year and both the male and female sing duets back and forth to each other and in response to their nearest neighbors.  When disturbed, they will pump their tail downward, droop their wings, and fluff up their feathers.  They nest low in small bushes or debris during the rainy season from April to October.  They usually lay two eggs and both parents incubate and tend to their young.

We would like to thank both Alan Dahl from Focused on Nature and Gianfranco Gomez from the Drake Bay Rainforest Chalet for allowing us to showcase their photographs.

Birds

Birder's Challenge

Riverside Wren nest by Cheryl Chip & Jim Tamarack

For those of you who may remember, I posted a feature on the Riverside Wren (Thryothorus semibadius) back in April.  It was one of my first postings for the then new Friends of the Osa’s blog The Osa Chronicles and a few of you commented on both the nature history and photography by Gianfranco Gomez.

One of the species ecological behaviors I wrote about was of reproduction and nesting.  When I spoke about the nest of the Riverside Wren this is what I said:  “Nests are bulky globe structures with a roof and a vestibule (so to speak) not only used for raising young but also for sleeping at night any time of the year by either one individual or as many as possibly 3.  This species can be found nesting from December to August, nine months out of the year!”

Not long after this posting some friends and residents of the Osa Peninsula Jim Tamarack & Cheryl Chip saw the posting and sent me this photo they took of a Riverside Wren roosting in its nest at night near their home.  This photograph was taken in the month of December, but it also could have been taken any time of the year.

Riverside Wren at Drake Bay

Now, the position of this bird has had many of us puzzled for some time so I am inviting commentary from you all.  It looks like the bird is camouflaging itself in the nest, but how?  The Riverside Wren has barred black-and-white stripes only on the breast and belly while the back is solid rufous.   It’s as if it were laying on its back.  Are there two birds here?  Is this the Riverside Wren?

OK birders, its time to chime in.  I am waiting for your opinions and comments.

Science and Research

The OBC and studies into microhabitat preferences of focal group taxa

By: Zia Mehrabi, University of Oxford.

The Osa Biodiversity Center (OBC) provided a brilliant opportunity for biological research at an accessible location bordering Corcovado National Park (CNP). CNP represents the largest remaining tract of tropical lowland forest left standing on the pacific coast of Central America. The Osa Peninsula is phytogeographically unusual with high floral species diversity of an estimated 500 species of woody plants and exhibits high primate abundances as well as being home to charismatic large felids such as puma and jaguar.  The work undertaken at the OBC during April 2010 primarily aimed to clarify insights into the microhabitat preferences of particular dung beetles (Coleoptera: Scarabaeidae: Scarabaeinae) identified in earlier study investigating the fidelity of ecological methods used for inventorying insect functional groups at Sirena Biological Station (CNP) during the months of July and August 2009.  In order to efficiently and cost effectively map diversity it is widely recognised that the use of indicator groups is necessary. The sensitivity of Dung Beetles to light, soil type, moisture, temperature, leaf litter, structural complexity, vegetative cover, and resource type are widely recognized, advocating their utility as an indicator of the influence of abiotic environmental parameters on patterns of diversity in tropical ecosystems on a global scale. In order to map spatio-temporal distributions of biological organisms it is important to measure habitat variables on the scale at which they influence the taxa studied. If the habitat is not defined from the perspective of the organism then inference made from data reporting environmental influences on distribution of populations may be inaccurate.  The material generated during the study at the OBC will be identified at the Oxford University Museum of Natural History. It is an exciting prospect that the work at OBC may back earlier work that has identified a microhabitat preference of dung beetles on trap placement, work that potentially has serious implications for sampling methodologies currently employed in comparative ecological work which  aims to report the influence of deforestation and habitat degradation on tropical biodiversity.

All photography by Zia Mehrabi on night walks at OBC during April 2010

The accommodation facilities at the OBC are superb, with comfortable beds, clean running water and delicious food. Furthermore the staff are extremely friendly and helpful, facilitating communication with the local community and achievement of research objectives. In addition, accessibility from the nearby town of Puerto Jimenez and contact via satellite connection ensure ease of logistics. There is a nicely set out trail system that provides some great tracks for night walks where a plethora of insects , arachnids and reptiles may be easily observed and photographed. Overall I was very happy in the time I spent at the OBC and would recommend it to other researchers wishing to explore this interesting region of the world.

Birds

Featured Bird: Common Pauraque

Common Pauraque by Karen Leavelle

Have you ever been out at night driving along a country road and been startled by red ember eyes darting across the hood of the car, and then to have it happen every few hundred meters or so?  If you are driving anywhere on roads, especially dirt roads, from South Texas on down to Argentina you are bound to see the Common Pauraque (Nyctidromus albicollis).

Here on the Osa Peninsula on the road to the Osa Biodiversity Center it is a common sight to see the nocturnal nightjar hunting along these roads or other open areas at dusk, dawn or during the night.  As twilight approaches, Pauraques will position themselves on the ground which is a good spot from which to see insects backlit against the night sky, or on a favorite perch sallying around in search of the nights meal.

They have very small beaks yet large gaping mouths with which to scoop up large insects such as beetles, moths and fireflies.  The bristles around the face resembling whiskers are modified feathers which are highly tactile and controlled by muscles and are used to help hunt insects at night.  They are likely there to also keep out-of-control insect legs and wings out of the bird’s eyes!  This 11” (28cm) bird also has low wing loading which means their body is proportionally small to their large wings which makes them powerful flyers through wooded areas especially at night.

The genus Nyctidromus gives the Common Pauraque its first name “night runner” describing its nighttime ground foraging behavior and the species name albicollis is in reference to its white throat patch.  In various parts of Central America it is commonly refered to as “Don Pucuyo” or “Caballero de la noche” for its association with love.  Some parts of Costa Rica call this species “Tapacaminos comun” meaning common road coverer.  Here on the Osa Peninusla it is known as Cuyeo.  There is lots of legend surrounding this and other nighthawk (goatsucker) species related to both love and darkness.

Its cryptic browns, tans and buff coloration make this bird hard to see unless you are about to step on it.  It will flatten itself close to the ground when danger approaches and then will flush at the last moment.  It will then keep its eyes slightly open as you can see from the photograph to keep an eye on the possible ensuing predator.  It places its nest of two eggs right on the ground with no pomp or circumstance usually in shady wooded areas.

So why hunt from a country road exactly?  Studies have shown that Pauraques will actually sit along the side facing the road and are more likely to be found there during a full moon which reflects light on the dirt surface making it easier to find and catch insects.

You can find this and other photographs from Alan Dahl at Focused on Nature.  The light morph bird was taken by me along the trail up on our Arbolito property just last week early August.  This bird flushed from my feet and was very cooperative with her photo shoot allowing me to get quite close so I could bring you her image today.

Birds

Featured Bird: Blue-crowned Motmot

Blue-crowned Motmot by Alan Dahl

The Blue-crowned Motmots (Momotus momota) have been spending a lot of time around a Nance tree (Byrsonima crassifolia), a prolific fruit producing tree in the garden here at Friends of the Osa’s Osa Biodiversity Center.  Lately there have been quite a few hanging around giving their distinctive soft low pitch “moot moot” call at dawn which has sounded like a large choral group, each bird with its own perfectly timed solo, and the group never missing a beat.  With the Nance fruiting right next to the house, one of them actually flew through the front door the other day making me realize that it was time to share this species with you on the blog.  Oh and by the way, he or she did find its way out of the house fairly quickly.

In this species the male and female look alike and as you can see from Alan Dahl’s photograph, they are brilliantly colored.  Motmots in general have two very distinct features worth noting: the racquet-shaped tail and a heavily serrated bill.  The tail is more than half the birds total length and has two long central feathers.  During feather preening sections of the tail barbs fall off leaving the exposed vane.  The tip of the feather or the racquet remains intact forming what looks like a racquet head.  Motmots are famous for slowly and methodically swinging their tail feather back and forth like a pendulum.

The bill has tooth like serrations allowing them to take small snakes and lizards as well as other insects and tear them apart.  They also accompany army ant swarms picking off what the other birds kick-up from the ground.  And yes, they like fruit.

A third and very interesting characteristic of the Motmot is the fact that they dig their nest into burrows.  They are most closely related to Kingfishes and todies which also dig into burrows.  Motmots excavate tunnels in the bank of a road or stream or in the side of a pit or hollow in the ground.  Their nests are unlined and can wind as far back as 5 – 14 feet (1.5 – 4 meters).  Now I don’t know about you all but I have a hard time seeing such a beautiful majestic bird digging a long tunnel in the dirt and coming out looking that good, but I truly hope to see it someday.

You can see the Blue-crowned Motmot all over Costa Rica, and at least at the moment, all over Cerro Osa on the Osa Peninsula.  You can also find them from Mexico down through Argentina and in just about any type of habitat most often perched in the shade saying “moot moot, moot moot”!

We would like to thank Alan Dahl for allowing us to showcase his photographs.  You can find his work at Focused On Nature.