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!


National Jaguar Initiative

Blog Post by Juan Carlos Cruz Díaz, Feline Program Coordinator

When we talk about the jaguar, it is difficult to distinguish the many vital roles this iconic species plays. All throughout Latin America, the jaguar is deeply rooted in the indigenous culture. From a cultural point of view, it has been part of many artistic and cinematic works. From a conservationist point of view, it has been considered everything that a species can be: an umbrella species, a flagship species, a keystone species, an indicator species, and an apex predator.

In spite of its huge importance, however, we know very little about the species’ ecology and what is necessary for its conservation.

Due to the jaguar’s biological characteristics, research techniques necessitate much physical, economic, and logistical effort, and thus, it is no easy task to study them. However, when these efforts are realized, every result is significant and further augments our knowledge of biology and ecology.

This year in Costa Rica, Osa Conservation worked with partners to analyze the results of the first national jaguar initiative, which brought together jaguar researchers and studies throughout the country to synthesize what we know about this important species at the national level.

The larger initiative is called: “Jaguar conservation in Costa Rica throughout the integration of species registration data and habitat modeling.” It is a product of the Promotion of Participative Management for Biodiversity Project, led by the National System of Conservation Areas and the Japanese Agency of International Cooperation with the collaboration of Costa Rican jaguar researchers.

In over a year of gathering information from diverse jaguar studies (including research from camera traps, excrement studies, road presence, sightings, records of predation of cattle and sea turtles, tracking collars, and genetic material provided through excrement), meetings, seminars, map creations, and expert consultations, the initiative obtained results that widen our knowledge of the state of jaguar conservation.

An essential part of this initiative was being able to describe the current distribution of the species and modeling ideal habitat conditions, which established guidelines for determining conservation priorities for this endangered species going forward.

Utilizing current species distribution registries and variables (habitat, human impact, and climate) chosen by experts, the initiative predicted suitable habitats for the species throughout the continental territory of Costa Rica.

Map predicting suitable habitats for jaguars in Costa Rica.

Zones were identified with the best habitat conditions for the jaguar. They were delineated as focal areas with the principal objective being to evaluate the availability and characteristics of existing biological corridors at the national level in order to connect these areas.

The focal areas identified are located largely in the Talamanca Caribe and Amistad-Pacifico region, the Caribe-Norte, the Osa, and the Cuanacasta and Volcanic Mountain Ranges.

The findings of this study represent recent knowledge about the distribution of the species and its ideal habitats, based on registries of presence/absence, relying on the participation and evaluation of national and international experts studying the species. Bringing together this diverse array of studies and researchers is unprecedented in Costa Rica. It constitutes the starting point for developing a strategy that prioritizes medium-term conservation efforts for the sake of obtaining a better and more efficient response to the conservation needs of the species, based on biologically and scientifically supported information.

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