Conserving the last populations of the Golfito Robber Frog

Blog Post by Hector Zumbado-Ulate, Alvaro Ugalde Scholarship Awardee

My name is Hector Zumbado-Ulate and I’m one of the awardees of Osa Conservation’s Alvaro Ugalde Scholarship. Currently, I am pursuing a PhD in ecology and evolutionary biology at Purdue University. Since I started my studies in biology, I felt very attached to amphibian conservation projects, especially those helping species which are currently endangered by anthropogenic causes. For that reason, I wanted to work with the critically endangered Golfito robber frog. Specifically, I want to examine why this species persists in remnant populations after going extinct in much of their historical home range. Such information is valuable to develop adequate conservation policies that can be implemented to protect these populations and encourage their expansion back into their historical habitat range throughout Costa Rica. In particular, I am studying host-parasite interactions between endangered frog populations and the fungal parasite Batrachochytrium dendrobatidis (Bd), which causes chytridiomycosis, a potentially deadly disease that threatens many amphibian communities. At least 90% of the 34 species of robber frogs have catastrophically declined or have become completely extinct since the 1980s, likely due to this taxa’s high susceptibility to this disease. I am also quantifying how environmental stress caused by climate change affects reproduction, population dynamics, and susceptibility to chytridiomycosis in remnant populations of critically endangered robber frogs.


The critically endangered Golfito robber frog (Craugastor taurus) in Punta Banco, Golfito.

In the last decade, some populations of the Golfito robber frog have been rediscovered in the peripheral areas of their historic home range. This suggests that 1) peripheral populations may have survived environmental threats that affected core populations, 2) the slow recovery has made these declined species almost undetectable across their range, and 3) there might be more cases of remnant populations that still thrive but remain undetected. Remarkably, rediscovered remnant robber frog populations coexist with B. dendrobatidis without experiencing chytridiomycosis and the proposed project aims to identify the mechanisms that allow these susceptible frog species to coexist with this lethal parasite.

With the help of volunteer field assistants, I am conducting habitat monitoring and parasite detection to evaluate the risk of extinction of remnant populations three times every dry season. Specifically, I am sampling fast-flowing stream networks in Punta Banco, which are the only known streams that sustain stable populations of the Golfito robber frog. I am also monitoring and continuously looking for the Golfito robber frog in streams in the localities of Uvita, Golfito, and Rincon de Osa (this latter location historical represents the most abundant populations of the Golfito robber frog before its decline during the 1980s and 1990s).

In every stream, we are conducting multiple linear transects. On every trip to the field, we characterize every transect by measuring several environmental variables such as air temperature, humidity, stream width and depth, and canopy cover, among others. We catch individuals of all occurring frog species and measure the snout-vent-length and body mass. We also swab the frog’s skin to collect Bd zoospores. Moreover, we analyze water samples to determine if the concentration of Bd zoospores varies across stream location.

Stream monitoring in Rincon de Osa


Stream monitoring in Uvita.


Filtering of water samples from Quebrada Agua Buena in Rincon de Osa, with the aim of detecting Bd zoospores.

I am combining my research with education and outreach activities in order to share our findings with the public and policy-makers, with the goal to create optimal conservation policies for these species. In the long term, I aim to:

  1. Propose and implement in-situ strategies to increase the survival of adult frogs and recruitment of juveniles in remnant populations.
  2. Expand the range of declined robber frogs across their original home range.
  3. Establish a long-term monitoring project in collaboration with volunteer local groups, students, and professionals.

Invited speaker at Universidad de Costa Rica, recinto de Paraiso in June, 2018. Here I presented this project to ecotourism students.



Teaching Mangrove Awareness in Térraba-Sierpe

Blog Post by Monica Espinoza, Marine Conservation Scientist

The Térraba-Sierpe Wetland presents the most productive and biodiverse mangrove ecosystem in the South Pacific of Costa Rica. However, not everyone knows the importance of this habitat in our day to day life. For this reason, we decided to celebrate World Mangrove Day with the School of Ajuntaderas, Sierpe.

Our special guests were the children of this community who learned about the importance of mangroves, fire prevention and waste management. It is important to recognize that boys and girls are carriers of information. They must be listened to and can transmit these messages to the people around them. In this way, people will be aware of the importance of the natural environment in which they live and generate a culture of protection of the wetland.

During the activities, Osa Conservation’s team taught that mangroves are tree species capable of growing and tolerating high salt concentrations in intertidal waters. In addition, they have a root system that offers a sanctuary to small fish and protect the coast from strong weather events.

Our partner ACOSA presented a captivating story to the children about the prevention of forest fires. And to the surprise of all the students, the protagonist of the story Toño Pizote (the mascot symbol of environmental conservation) made an appearance, which brought joy and excitement to everyone.

The Municipality of the Osa collaborated with a dynamic to learn to differentiate the various types of waste and management strategies in order to combat the large amounts of garbage that are produced every day (Costa Rica consumes 323 thousand tons of plastic materials per year). In addition, we taught them how to minimize the consumption of single-use plastic products that end up on beaches and in oceans (80% of marine pollution is plastic) by using reusable bottles and cloth bags and rejecting straws.

Education is an essential tool to generate change towards the conservation of marine-coastal ecosystems. This is why it is essential to get the necessary information to all those who affected, either directly or indirectly. Coastal communities are among the ones most affected by the effects of climate change, facing threats of rising sea levels rise and strong storms. Thanks to green infrastructure such as the mangrove ecosystem, these impacts are mitigated, protecting threatened communities.

It is important to continue creating these types of events for school children in order to raise awareness about the essential mangrove ecosystems and to continue protecting these habitats, not only because of their biological importance, but also because of the local community’s people who depend on them.


Plastic Prevention in Paradise

Blog Post by Noelia Hernández, Marine Programs Coordinator

When you visit Osa’s beaches of Piro and Peje Perro for the first time, it feels like a scene straight out of a movie; you can picture a shipwreck landing on one of these beautiful, untouched beaches, and the tourists becoming surrounded by nature, calm, and beauty. The trees, the mist in the background, the birds in the sky, the breaking waves, and the opportunity to see incredible species like turtles and whales all make you think that you are in a dream or in a movie. Unfortunately, a return to reality confirms that, like many other beaches, these remote paradises suffer the presence of plastics.

Plastics found on Peje Perro beach during sea turtle patrol.


A large piece of foam found on Peje Perro beach.

How is it possible that such an idyllic site has so much plastic? Yes, we already know that trash finds its way to the sea and, by currents, returns to the coast. But how have we arrived at this extreme, throwing 8 million tons of refuse into the oceans each year? To give you an idea, this amount of trash is equivalent in weight to 800 Eiffel towers. With these statistics, it is not surprising that five large trash islands have formed in the ocean. But what is surprising is the dimensions of only one of these islands in the Pacific is approximately 1.6 million km2, three time the area of France. Yes, you read that correctly: three times France! It’s hard to imagine, but you don’t have to think too much about the data to recognize the magnitude of the problem.

The amount of plastic collected in 5 hours by the sea turtle research assistants.

Thus, Osa Conservation is dedicated to keeping Osa’s beaches pristine, while finding ways to tackle the larger plastics problem. As part of a recent beach clean-up, three members of our sea turtle conservation team collected close to eight 100 liter bags of trash…in only a few hours! On separating the different types of refuse for recycling, we decided to analyze the labels and caps of the collected plastic bottles, and found that the majority of these plastics came from Asia.

Members of the marine program and Rios Saludables program separating different plastics for later recycling.


Results of analyzing the origin of the caps and labels of the found bottles. Photo: Mónica Espinoza.

Seeing all that trash in a place like Playa Piro or Peje Perro, I start to wonder if it’s true that there will be more plastics than fish in the ocean by 2050. Imagine having an ocean completely filled with trash. No thank you! The good news is that if we use all our effort, there is still time to make a change, and there are already measures that have been taken in this regard. In fact, the Osa region has been a pioneer in Costa Rica in eliminating plastic from its properties, and on the national level, all single-use plastics will be prohibited by 2021. Small daily gestures—like bringing your own bag to the supermarket, not using straws or disposable silverware, using reusable water bottles, and avoiding single use containers—will make a huge impact.

Members of the Marine Program and the Rios Saludables Program.

Will you join us in the battle against plastic? #BreakFreeFromPlastic #ForgetPlasticIsFantastic

Note: For those who are skeptical, or just curious, we invite you to read this study by Jambeck and collaborators in 2015, as well as the work done by Lebreton and collaborators that was recently published in Scientific Reports.


Silent Night Walkers

Blog by Juan Carlos Cruz Díaz, Feline Program Coordinator

It’s 5:30 am and the sun is rising above the Dry Forest of Guanacaste in northern Costa Rica. Researchers in Naranjo beach in Santa Rosa National Park in Guanacaste Conservation Area are getting ready to survey the beach. They walk along the shore looking for evidence of the presence of jaguars. Unlike in the Osa, at this beach it is common to encounter tracks left by jaguars who patrol the beach looking for prey.

Jaguar tracks along Sirena beach in Corcovado National Park.

Not many people know that sea turtles are a common prey for jaguars. Sea turtles are quite fast and agile animals in the ocean, but quite slow and clumsy on land. So when the females come to lay their eggs on shore, they are quite helpless, making them perfect prey for a jaguar.

In order to track this type of activity, researchers walk along the beach often in the mornings, documenting tracks of sea turtles who came to shore the night before. Researchers can not only tell which sea turtle species were present based on their tracks, but even more importantly, whether or not the turtle returned to the ocean. With no clear return path, it is likely the turtle was predated the night before and the researchers will then begin their search for a carcass as proof.

Sea turtle tracks in Naranjo Beach, Guanaste Conservation Area.

Guanacaste Conservation Area is one of the few places in Costa Rica where sea turtle predation by jaguars has been reported, as well as Tortuguero and Corcovado National Park. In fact, our neighbor, Corcovado National Park, was the first place where this phenomenon was reported. In the 1990s, researchers found that jaguars in the park changed their behavior, transitioning from diurnal to nocturnal during certain times of the year, which happened to coincide with the peak times for sea turtle nesting at the beaches in the area! This change suggests that sea turtles are a regular natural prey for jaguars and probably have been for thousands of years.

A camera trap picture of a jaguar with its olive sea turtle prey on Naranjo beach in Guanacaste Conservation Area.

Even though sea turtle predation is common along areas where jaguar distributions overlap with sea turtles, this natural predation does not represent a serious threat to sea turtle populations. Jaguars take about 30 turtles per year in Guanacaste and about 20 per year in Corcovado. Jaguars are also the only big cat known for this behavior, probably because they have the strongest bite among all the big cats, and crushing the turtles shell demands great strength.

It is now eight in the morning back in Guanacaste and researchers have just found a green sea turtle that was recently killed. After identifying the species, taking photographic records, and collecting shell measurements, researchers mark the shell as to not count it again in future surveys. Finally, they set up camera traps on site in hopes of identifing the jaguar that will come back to feed later that night.

Jaguar and olive ridley in Naranjo beach in Guanacaste Conservation Area (Photo credit: Alonso Sánchez).

While this specific jaguar behavior has only recently been studied, it has brought new and exciting information about variables that might explain other behaviors about jaguars, including habitat use and even tolerance of other jaguars in the same site. Such research is also helping to create awareness of the delicate balance of ecosystems and how species that may seem to be very different depend highly upon one another within the ecosystem.

Osa Conservation has collaborated with Corcovado and other national parks and partners as part of the Osa’s Camera Trap Network. Camera traps help research projects like these to collect evidence and learn more about the behaviors of Costa Rica’s wildlife and wildcats. To learn more about the Camera Trap Network and the work that Osa Conservation does to study and protect jaguars and other big cats, click here.




Never Too Old to Be a Junior Park Ranger

Blog Post by Hilary Brumberg, River Health Program Coordinator

It was a windy fall day when I joined a group of budding field researchers and nature enthusiasts to visit the Rocky Mountain National Park for the first time. As we hiked the trails, I was in constant awe of the breathtaking front-range views and the abundant wildlife, ranging from elk to butterflies to marmots to hummingbirds. But it wasn’t just the wildlife that left an impression on me.

As I was browsing the gift shop before leaving, I happened upon a Junior National Park Ranger induction ceremony that was taking place. As the middle schoolers received their badges, I could see how proud and excited they were, and imagined how happy I would have been if, at age 11, I could help protect the incredible ecosystem I had just walked through.

Flash forward, I’m at another Junior National Park Ranger induction ceremony. This time, however, the students are Costa Rican, and they are joining the Guardaparque Junior program. Modeled after the U.S. Junior National Park Ranger program, Costa Rica’s Guardaparque Juniors program teaches students to “Explore, Learn, and Protect!” national parks and reserves in Costa Rica. The program aims to form the next generation of community leaders and conservationists by educating them on the complex interactions between society and the environment. The National System of Conservation Areas (SINAC) is spearheading this pilot program with the support of local non-profits, including Osa Conservation.

Hilary teaches Guardaparque Junior students to identify macroinvertebrates, mini might-beasts whose diversity indicate river health, in the river that provides most of the water for the La Palma aqueduct system.

The first workshop for Guardaparque Juniors from La Palma High School focused on freshwater, from montane forest streams to home taps. Because freshwater conservation incorporates ecological study with social, economic and political factors, we at Osa Conservation thought it would be a good way to introduce the students to complex conversations about conservation. To illustrate how freshwater conservation affects their lives, administrators of ASADA La Palma (local aqueduct administration organization), SINAC and I took the students to the source of the stream that provides water for most of the La Palma area. I felt like a Junior Park Ranger myself as we trekked through lush old growth forest to reach where the stream fed into holding tanks and an automated chlorination system—the source of the water whenever the students turn on the taps of their kitchen sinks at home.

Guardaparque Junior students, ASADA La Palma administrators and SINAC environmental educators identify macroinvertebrates they collected from the river.


Guardaparque Junior students performed a pH test and found that the river water chemistry was neutral, which is in the healthy range.

To confirm the health of the stream, the students and I worked together to analyze the water chemistry and searched the rocks and leaf litter for macroinvertebrates, insect larvae and shrimp whose diversity indicate the health of the river. Then we followed the river downstream as it passed through cattle pasture and the bustling center of La Palma, where we repeated our mini-experiment. We found significantly lower macroinvertebrate species richness, which demonstrated how the river is adversely affected by deforestation and urbanization.

Renowned Osa botanist Reinaldo Aguilar explains that healthy forests are essential to river health because they provide nutrients, prevent erosion, regulate temperature and filters toxins.

Programs like the Guardaparques Junior and the Junior National Park Rangers are essential to nurturing the next generation of conservationists because they engage students and bring them outside. By the end of our workshop, the Guardaparque Juniors had a new perspective of how the health of the river and the health of La Palma’s residents are inextricably linked. The next time they turned on the tap, it would be with the understanding that they have a part to play in keeping their town’s water clean and preserving the health of the forest that provides it.


Mangrove Restoration Actions in the Térraba Sierpe National Wetland

Blog Post by Luis Carlos Solis, Mangrove Restoration Coordinator

The Térraba Sierpe National Wetland encompasses the largest mangrove forest in Costa Rica with an area greater than 16,000 hectares which, due to its biological importance, was declared of international importance by the International Convention on Ramsar Wetlands. In this protected area, mangrove resources have been used since pre-Columbian times when indigenous communities extracted dye from the bark of the red mangrove (Rhizophora mangle) to dye their clothing.

A section of land cleared of invasive ferns

Currently, the inhabitants of the wetland base their economy on various activities such as the extraction of the “piangua” mollusk (Anadara tuberculosa), artisanal fishing, and the isolated production of various crops and livestock; however, in the past, the local economy was based on the extraction of wood for the production of coal, firewood and construction materials, which decimated the mangrove forest. As a result of this deforestation, the “negraforra” fern (Acrostichum aureum) has dominated the wetland, which is an opportunistic species that is difficult to eradicate. Due to its high density, it acts as a barrier to the natural growth of the mangrove.

A pianguero working on planting mangroves


A pianguero in a Mangrove Nursery

As a result of this barrier in forest regeneration, Osa Conservation is carrying out mangrove restoration actions through the project “Effective strengthening of mangrove ecosystems in Costa Rica and improvement of the quality of life of the local coastal population” with funding from ALDI SÜD and KfW-DEG. Osa Conservation is pursuing this project in conjunction with the Association of Piangueros and Marine Resources of Ajuntaderas (APREMAA) in order to promote the health, integrity and sustainability of a degraded ecosystem.

The Osa Conservation Team out in the field

These restoration actions are based on active management, a technique that uses human intervention to remove the barriers that prevent the natural regeneration of the mangrove. This involves removing the fern in order create a more favorable environment for mangroves at restoration sites. The project is also establishing mangrove tree nurseries in order to accelerate the recovery processes of the ecosystem. All these tasks are carried out in conjunction by different institutions and national and international organizations such as the Osa Conservation Area, the Osa Municipality, the National University through its Applied Tropical Ecology Laboratory, Bluesensus, Shore-Rainbow Export Processing Group, ICE Group-El Diquís Hydroelectric Project, and GIZ Agency, among others.

Cutting the ferns in a restoration plot

These efforts are part of a government policy for the conservation and recovery of wetlands as a fundamental element in the sustainable development of the communities that depend on them as a way of life. For Osa Conservation, it is a privilege to be a part of these efforts and to safeguard the fundamental services the wetlands offer.

The Universidad Nacional team


The Association of Piangueros members working to plant mangroves

To find out more about our work with mangrove conservation, click here.


Building our Marine Program: Connecting in the Osa

Blog post by Mónica Espinoza Miralles, Marine Conservation Scientist

For those passionate about the underwater world it is amazing to see how extraordinarily different the seas are around the world. This was the case for us:  Noelia Hernández, an oceanographer from Spain and Osa Conservation’s new Marine Program Coordinator, and myself, Mónica Espinoza, a marine biologist from Costa Rica and Osa Conservation’s new Marine Conservation Scientist. We had the opportunity to meet for the first time at Saladero Ecolodge, and from that moment, we realized that we both have a great affinity, passion and curiosity towards the sea. For this reason, we are extremely excited to be the new members of the Marine Conservation Program at Osa Conservation, to build on the local partnerships, and to protect this unique and special marine landscape.

The experience at Saladero Ecolodge started by taking a canoe and navigating through the calm waters of Golfo Dulce. Once across this incomparable tropical fjord with a depth of around 200 meters, you can see the Piedras Blancas National Park. Saladero is located right at the foot of this protected area, a site that immediately exhibits that special interaction between the sea and the land.

Saladero EcoLodge view from the sea

When we arrived, we had the opportunity to explore the primary and secondary forests that surround this beautiful hidden corner of the South Pacific, and to suddenly find the flow of the river that crosses and bathes the beautiful lands of the tropical forest and converges in the waters of the blue sea of Golfo Dulce. That is when we decided to venture in kayaks to be one with the river, to flow through its channels and be surrounded by nature. At the mouth of the Esquinas River, we found the complex mangrove ecosystem, a place of great diversity in flora and fauna and a refuge for future generations of hammerheads, also known as the guardians of Isla del Coco.

Mangrove forest perspective from the kayak

After that wonderful experience in this important carbon sink, the desire to enter the underwater world increased. So, we took our snorkeling equipment and dove to find the submerged paradise that many seek. The world below the sea surface is a place that captivates you, takes you out of everyday life and makes you live in the present where the connection with nature is magnified. This is where we had a magical encounter with a curious hawksbill sea turtle, which seemed to stop us in time and show us how magnificent these creatures are in their own way. Sea turtles are not only beautiful animals, but also show incredible perseverance and endurance. After all, they have nested on beaches for millions of years.

Noelia exploring a hard-coral formation

At the end of our little adventure we headed back to Saladero Ecolodge completely unaware of the encounter that awaited us. In a moment of rest on the kayak, we were appreciating the horizon and suddenly we observed a splash of water in the distance. We looked at each other excitedly, and when we looked closely we could distinguish around five dorsal fins that broke the surface tension of the water; they were bottlenose dolphins. Seeing one of the resident species of marine mammals in the Golfo Dulce feeding from our kayak was nothing short of spectacular. At the end of the day, this confirmed what we had read and heard about the Golfo Dulce, a home to many species, both resident and migratory, and a key site of essential ecosystems. Such an experience only reconfirmed our excitement and dedication to helping Osa Conservation expand a Marine Conservation Program to protect these incredible habitats. We look forward to sharing more information with you in the near future about this new program.

Monica kayaking on the way back to Saladero EcoLodge after sighting bottlenose dolphins

Sometimes it is difficult to imagine the amount of life that congregates right on the coast, but after this experience in Saladero, we are extremely enthusiastic about the new opportunities that await us. Even more important is to fulfill our mission to preserve what we are so passionate about and that we now call our new home.

If you too are interested in participating in the marine exploration of the Golfo Dulce and the Osa, check out our travel package offered here—join us for a few days exploring the rainforests, the mangroves, and waters of the Golfo Dulce. We hope to see you soon!


Osa Big Day 2018

Blog Post and Photos by Patrick Newcombe

Osa Conservation’s landscape is a mosaic of terrestrial habitats including grasslands, palm forests, reforested areas, secondary and primary forests, as well as aquatic habitats such as a ponds, rivers, lagoons and ocean. Elevation ranges from sea level to 1,083 feet (330 meters). This habitat and elevation range result in phenomenal bird diversity and illustrate the importance of the habitat conservation and restoration occurring at Osa Conservation.

June 25 was the first Big Day at Osa Conservation! In birding circles, a Big Day is a twenty-four-hour time period from midnight to midnight where a team tries to identify as many species as possible by sight or sound, in compliance with the American Birding Association’s official rules. Adding to the challenge, we planned a carbon-free Big Day without motorized vehicles. We found 135 bird species despite a three-hour downpour in prime birding hours! We would love to do a Big Day again during migration to include migrating species such as warblers and shorebirds, and we feel that we could break a much higher benchmark.

The Big Day Team

Our team consists of Thomas, Zac and Patrick from Osa Conservation, as well as Henry, a local resident, and Nito, a Costa Rican birding expert and owner of Surcos Tours. The excitement mounts the evening before as we discuss strategies and plans over dinner. “What do you think a realistic goal is? …80? …90?” “What time should we look for the crested owl?” “What do you think of walking up the river?”

The alarm goes off at 3:45 a.m. and we quickly pick up Crested Owl and Common Pauraque calls around the clearing around the Biological Station. And we are off!

We walk down to Osa Verde where we bird the farm fields interspersed with hedgerows and trees along with the reforestation arboretum.


Then, we continue along the former air strip reclaimed by marsh and grassland and along the ocean before heading back down the driveway to the entrance of Osa Verde.

Here we stop to enjoy Emilie’s delicious field breakfast of gallo pinto, fried eggs, and plantain (Emilie was awake even earlier than us to prepare our field breakfasts!). It’s still not 9:00 a.m. and we have birded an amazing seventy-four species, far surpassing our expectations! Nito comments that it’s a good thing that Osa Conservation has worked so hard to conserve this land and the wide variety of habitats, allowing us to find such a wide range of species.

Ruddy-Breasted Seedeater

Our plan is to head off to the primary and secondary forest where we anticipate quickly adding many forest species. But, as birders know, the results of a Big Day are often influenced by the weather. Before entering the forest, the torrential downpour begins and we rush along the trail to reach a shelter overlooking the pond known for its “frog explosions” after rainy nights. We hang out on the platform for an hour with only a Purple Gallinule making an appearance. Although realizing that most species will be hiding quietly in the rain, we decide to head out in the downpour and, luckily, spot a Green Heron as we leave the pond area on Discovery Trail. Just before, we had hiked the second half of Discovery Trail in the morning and seen twenty-three species but, disappointingly, now the birds are in hiding.

Reaching Piro River, we find the water level has risen significantly, but we decide to stick to our plan to head up through the river to look for an occupied Band-tailed Barbthroat’s nest, staked out by Patrick and Zac the day before. Piro River raises our spirits as we also spot a Fasciated Tiger-Heron.

The rain continues steadily and we head back along Discovery Trail. When we reach the Biological Station, everyone is gathering for lunch and eagerly questioning us about the Big Day.

After lunch, we head up Tangara Trail in hopes of seeing the Spectacled Owl that Patrick and Eduardo had found on Saturday. Our hopes are also set on finding a flock. Rainforest birding is tough because we often go long distances with few birds until meeting a flock where we have to pick out as many species as possible before it moves off.

The forest is quiet except for the Scarlet Macaws and Orange-chinned Parakeets making a racket. It is not until high up Ajo Trail that we encounter our first flock. What a reward: about fifteen species, including a Gray-headed Kite, fly in.

Nito suggests heading up towards Cerra Osa in hopes of spotting some birds of prey. Cerra Osa is at 1,083 feet (330 meters) above sea-level and consists of a reforested area where the tree cover is not as dense. We are rewarded by a Northern Bentbill and White-necked Puffbird, two very unexpected species, while also finishing out our honeycreeper sweep with a Green Honeycreeper.


White-Necked Puffbird

After checking out Cerro Osa, we head back down to the research station to reassess our list. Since we usually see Amazon Kingfishers and a Ringed Kingfisher lower down Piro River, we head down to explore the river some more, quickly snagging a few more species including kingfishers as well as the Scarlet-rumped Cacique and Golden-naped Woodpecker. Night is approaching, and Nito and Henry have to return to Puerto Jimenez. Osa Conservation’s first Big Day has come to an end.

An endangered Black-Cheeked Ant Tanager

It’s been a fulfilling day. Before coming to the Osa Peninsula I had participated in some Big Days as well as the World Series of Birding and was very curious to see what we could accomplish during a Big Day on Osa Conservation’s property. One hundred and thirty-five species far surpassed my expectations. Our list can be found here. (If you’re interested, here is a description of a Big Day during the World Series of Birding in New Jersey.)

More important than the overall number, the Big Day illustrated to me the engaged and motivated community at Osa Conservation. At lunch and dinner, many people asked questions about the Big Day and the birds, often wishing us luck during our search. We worked as a team in partnership with local guides, Nito and Henry, continuing our friendship. It is the comradeship within the team and at Osa Conservation that I will remember most.

Hopefully, there will be more Big Days at Osa Conservation to illustrate its amazing bird diversity and the importance of the conservation being done.


Bird Acoustic Project: Changing their tune

Photos and Blog Post by Thomas Meinzen, Restoration and Rewilding Intern and Birder

At the Osa Conservation Biological Station, mornings in the rainforest are full of sound—birds, frogs, insects, and monkeys all chirping, singing, buzzing and howling in a unique concert. But not far away, where staff and volunteers are working to restore and rewild deforested pasture lands, the dawn chorus strikes a different tune. Many of the low whistles, creaks, and croaks of the forest are being replaced by new, often higher-pitched sounds. As a researcher and intern with Osa Conservation, I’m studying how changes in forest structure (both deforestation and regeneration) are affecting animal sounds, focusing particularly on bird acoustic communication.

Birds play important roles in forest regeneration by pollinating flowers and dispersing seeds, helping rainforest plants to colonize disturbed areas. At the Biological Station, the White-necked Jacobin (left) is a key pollinator, and the Scarlet Macaw is an important seed disperser.

Birds have key roles in pollinating and dispersing the seeds of rainforest trees, and so are an especially important group for understanding the effects of forest loss and promoting forest recovery. Deforestation can alter bird communities in surprising ways. My research tests a theory called the “acoustic adaptation hypothesis,” which proposes that birds evolve their songs with characteristics that help them travel most efficiently through particular habitats. Because low pitches, which have longer wavelengths, can bend more easily around obstructions like trees, bird species adapted to forest loss may sing higher pitches in open pastureland than birds living in intact forests.

Birds of intact forests tend to have lower-pitched vocalizations with a narrower range of pitches, which can transmit better through forest understory vegetation. Here we can see this exemplified in the spectrograms (song pictures) of two species of tanagers common on the Osa. The Gray-headed Tanager, a forest understory species, has lower-pitched calls than the Cherrie’s Tanager, a species adapted to open habitats and edge.

To test this, I will head out into the beautiful primary forest to record the wide variety of birds that live there. I will be comparing their vocalizations with those of the birds living in the neighboring grasslands, where Osa Conservation is planting trees to restore these abandoned pasturelands. This research will help show how birds may adapt acoustically to changes in habitat, examining one way in which humans are impacting the sounds of the forest. Recording natural sounds and studying bird bioacoustics offers an exciting new way to assess wildlife populations for conservation on the global biodiversity hotspot, the Osa Peninsula.

Intern Thomas Meinzen in the field



Rare Encounters: Finding the Wrinkle-face Bat

Blogpost by Manuel Sanchez, Sea Turtle Program Coordinator and Wildlife Photographer

There are more than 114 species of bats, and around 80 of these can be found in the Osa Peninsula. Some are so common that they practically live in our houses, while others are so difficult to spot that when you encounter one, you are caught off guard and can’t help but think that no animal more incredible exists. It is said that the Osa contains more species of bats than the rest of Costa Rica, and I believe it to be true, because it has the best sites and resources. If I were a bat, I would of course choose to stay in the Osa.

I have had the opportunity to hold a bat in my hands, and to have helped on many investigations to identify bats and attempt to understand their ecology. I have been familiar with bats since I was a kid, ever since I had an encounter with a vampire bat. In reality, my mother was more scared than I was at the time…

A close up of a wrinkle-face bat; Photo by Manuel Snachez

But the bat that has always had my attention is called the wrinkle-face bat, or the “old bat.” One night I was working late at Osa Conservation Biological Station. It had rained for the first two hours of the night, and typically after such a rain many animals come out, especially the bats. Walking the coyunda river toward my house, there is a guava branch about three meters above the water. While searching for snakes and frogs there with my flashlight, I saw two eyes that didn’t belong to a frog, much less a snake. I approached very slowly as to not scare the animal, but in truth I was more scared of it than it was of me. I stayed with the bat for what felt like hours, watching how it ate a fichus fruit. It was a truly incredible experience: to think we have such beautiful and surprising animals in the Osa! I couldn’t wait for the excitement of successfully identifying the species, and I returned to the station to ask bat researcher Gloriana Chaverri, who happened to be staying with us at the time. Of course, she already knew the species from her years of work with bats. That was the only night I have seen the wrinkle-face bat in this giant forest, but the Osa continues to surprise me every day!

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