Panama’s diverse bird populations in rapid decline throughout tropical rainforests

By Sofie Kato

BARRO COLORADO ISLAND, Panama – Panama is home to one of the largest tropical rainforests in the world and holds thousands of species of biodiversity, including birds. However, climate change is increasingly threatening many species and their habitat. Through careful research done by scientists at the University of Illinois Urbana-Champaign, studies show that more needs to be done to protect the forests and their inhabitants. As the Earth’s temperature continues to rise, the number of birds in the forests will continue to decline unless the world comes together to stop it.  

AUDIO TRANSCRIPTION

SOFIE KATO, HOST: Panama has over 1000 species of birds, more than any other country in Latin America. But slowly, devastatingly, that number is dwindling as climate change and encroaching development eradicate their ecosystem. A group of scientists at the University of Illinois Urbana-Champaign conducted a study to find out more. From 1977 to 2020, they studied 57 species of birds that live above the tropical forest floor.  

COREY TARWATER: So we know that temperatures are going up in Panama, we know that precipitation is changing, and we know that both of those things seem to be impacting bird populations. 

KATO: Dr. Corey Tarwater is an assistant professor in the Department of Zoology and Physiology at the University of Wyoming.

TARWATER: The most surprises is that what we found is that even in these large protected tropical forests, the abundance of 70% of understory birds is declining, has declined over these last 44 years. 

KATO: Scientists have discovered that the number of birds living in these dense tropical forests has declined over the past 50 years. Out of the 57 species studied, they found that 40 species are diminishing, like the speckled mourner. Only two species of birds in the study increased, the blue chested hummingbird and white whiskered puffbird. 

TARWATER: So we tend to think of these large tracts of forests as really bastions of biodiversity, right? That they should be okay and all populations should be healthy. And instead what we found is that even in this intact forest, the majority of birds are declining.

KATO: According to the Rainforest Foundation US, a non-profit organization dedicated to protecting indigienous lands, nearly 63 percent of Panama is arboreous, or wooded, making it the most forested country in Central America. Its tropical climate and position on the isthmus, connecting Central and South Americas, allows it to host high levels of biodiversity. As a result, scientists come from around the world to research anything from the adhesion of insects on leaves to the relationship between ants and birds.

TARWATER: Birds are incredibly important for the ecosystem. They’re seed dispersers and they’re pollinators, they help structure plant communities.

KATO: The red-capped manakin is one of the most common species of birds in Panama, and an important seed disperser here. In the study conducted, it showed the greatest decline over the 50-year period, with 23 caught in 1977, and only nine caught in 2020. 

KATO: Of the many forested areas in Panama, one under particularly intense study by scientists is Barro Colorado Island, a land mass created in 1913 when all the surrounding valleys were flooded to create the canal. Barro Colorado is a 3,700-acre piece of land including five peninsulas. That’s a couple thousand acres larger than the city of Miami.  It is home to about 400 species of birds and close to 500 species of trees. The island, operated by the Smithsonian Tropical Research Institute in Washington DC, allows scientists to study the tropics up close.

TARWATER: Obviously birds are important in terms of structuring ecosystems. So when you lose birds, you lose plant species, right? And we rely on a lot of plants for the fruit that we eat for the medicines that we get. Tropical forests represent two thirds of the world’s biodiversity. And if we lose them again, we lose a lot of the potential medicines we’re going to have in the future. We’re going to lose huge amounts of biodiversity and food and all sorts of stuff. 

DR. JEFFREY BRAWN: So when you mist net, those are nets that you put in the understory of the forest and the birds can’t see them, and they fly into the nets. 

KATO: Dr. Jeffrey Brawn, professor in the Department of Natural Resources and Environmental Sciences at the University of Illinois Urbana-Champaign, has studied the birds that inhabit Barro Colorado Island since the late 1980s. He explained their primary research method, called “mist netting,” which involves capturing and tagging birds for continuous study.

BRAWN: And so you go and you pull them out and you get them and you get them in your hand. And then we band them with numbered-like bands. And so when you do that, you can find you can sort of model those data and estimate survival rates and just a lot of things about their population biology. 

KATO: Scientists conducted their study on a 54,000-acre plot of land in Soberanía National Park, located 15 miles away from Panama City. Thirty five of the 40 declining species, such as the black-faced antthrush and tawny crowned greenlet, lost more than 50% of their original population over the 44-year period. This was alarming because – despite the fact that there was no fragmentation and no change in land use – the bird populations were still dropping dramatically in the park. According to Dr. Tarwater, one of the main causes of decline for these species, is changes in habitat.

CHELINA BATISTA, RESEARCHER AT BARRO COLORADO ISLAND: I love the hawks and I always find a hawk.

KATO: Chelina Batista is a biologist who has served as a guide on the island for the past 21 years. Her greatest passion is the study and preservation of birds.

BATISTA: The first time that when I hold a hawk that we catch in a nets. It was kind of scary because it was big; was pretty big. But I hold it and it feels so good to have it, that bird, because it’s amazing. In general, have a bird in the hand is amazing experience. 

KATO: The crested guan is a near-threatened species due to habitat loss and hunting within its range.

BATISTA: That’s a crested guan. When those birds are coming back in a place, you have to remember that before the canal construction, Chagres River was crossing over here and the people help plantations of corn or plantains or other crops. And the people hunt over here. They were looking for those birds, the crested guan. All of those birds feel afraid of the human. But now, you find them here, after, I don’t know, 20 years or so, and they feel OK with the people. 

KATO: There are some hypotheses into why birds in the forests are declining. Some scientists studying arthropods have noticed a decline in insects, and since these are such a large part of a bird’s diet, this may be one of the causes of decline. 

BRAWN: You know, food’s a possibility. It’s possible that over the long term, there’s been some sort of contaminants that, you know, there’s a lot of agriculture around that park. It could be that pesticides have come in the streams that come into the forest. It’s a possibility. We don’t know, but it’s a possibility. There may be more avian malaria. Birds get malaria a lot. And there’s a lot of avian malaria for those species. Usually they don’t die from it. But the point being, it could be disease, too. We just don’t know. So there’s a lot of things that still need to be looked at.

KATO: A few select species in Panama, like the olive-striped flycatcher, are affected by loss of regional connectivity. Typically a higher elevation species known to make seasonal movements, the olive-striped flycatcher lost 98 percent of its original population.  

KATO: According to the conducted study, climate change and differences in annual rainfall have contributed to the reduced survival of tropical birds. Nearly one-third of 20 common bird species exhibited reduced population growth rates in response to longer dry seasons.

TARWATER: There’s lots of different things that can be done to sort of, from the local scale to the global scale. So kind of at this global level, if we can do things to reduce the speed at which climate change is happening, that’s going to really help animals try to keep up. Another thing that we can do on these larger scales is maintain more habitat connectivity. There’s also, of course, reducing deforestation, even doing little things at the individual level in terms of planting trees in areas that have been deforested or thinking about where you get your coffee from, isn’t it? And is it from a coffee place that uses bird friendly practices? There’s lots of types of things that people can be doing at that local scale.

KATO: It is important to do what we can to help protect bird species and their habitats. This is Sofie Kato, reporting from Panama for Northeastern University.