Birds by Day, Bats by Night: Paired Long-Term Census of Bats and Birds Starts in Panama

Research teams studying bats and birds gather in Panama’s Soberanía National Park to celebrate the launch of a long-term census of bats designed to complement the bird census, which will celebrate its 50th anniversary next year

Early in the morning on Monday, March 10th, 2025, two groups of tropical biologists – the bat research team from the Smithsonian Tropical Research Institute (STRI) and the bird research team from the University of Wyoming – met on a muddy dirt road deep in Panama’s Soberanía National Park. They gathered to celebrate the start of an exciting new research project: a long-term biannual acoustic and mistnetting survey of Panama’s Neotropical bats (LongBAT). The new survey will take place twice a year – every dry and wet season - at three sites on Barro Colorado Island (BCI) and three sites on Pipeline Road. The Pipeline Road sites are in the Limbo plot and complement the long-term biannual bird census run by Corey Tarwater, a professor at the University of Wyoming and STRI Research Associate and her team, which celebrates its 50th anniversary next year.

Why study birds by day, bats by night?  And why conduct the same surveys year after year for decades? As STRI staff scientist and the director of the Smithsonian Bat Lab, Rachel Page, explained, one of STRI’s key strengths is its long-term studies of tropical plants and animals. Without systematic long-term surveys, it’s hard to know if populations are changing, and if they are, when those changes occur, and if they are related to factors in the environment like severe weather events, changes in rainfall, or shifting temperatures.

This biannual bat census will give us the power for all kinds of collaborative comparisons over time,” Rachel Page said. “We'll be able to look year after year at how changes in the environment and changes in other taxa affect bats, which are key players in tropical ecosystems.”

Bats will join the ranks of other well-monitored taxa that have been systematically surveyed at STRI for decades. The tree census that began on Barro Colorado Island (BCI) in 1980 is now one of 78 standardized studies in 29 countries around the world that are being used to understand how global change affects forests through the Forest Global Earth Observatory (ForestGEO) initiative. Barro Colorado Island also hosts long-term monitoring programs for insects, an initiative led by STRI scientist Yves Basset, as well as long-term studies of the populations of lizards, monkeys, ocelots, and more.

Birds were one of the very first groups of animals to be regularly monitored at STRI. Records go back nearly 100 years. Biannual censuses on Pipeline Road, a road parallel to the Panama Canal within Soberanía National Park, were started in 1977 by James Karr. This long-term research has shown that bird species are changing over time, with changes in the abundance and population growth of many species.

Camilo Calderón Acevedo, Colombian mammalogist and STRI postdoctoral fellow, leads the LongBAT project. He is currently working on Barro Colorado Island with veteran bat researcher Marco Tschapka, co-director of the long-term bat monitoring initiative, and his team from the University of Ulm in Germany. The team was excited to find among the first bats captured on BCI the wrinkle-faced bat (Centurio senex), a spectacular sight and one of the rarest species in the area.

One of the people attending the inaugural celebration on Pipeline Road was Erin Kennelly, James Karr’s granddaughter, who fell in love with Panama when she and her family visited during a symposium to celebrate 100 years of research on Barro Colorado in June 2024. She is now volunteering with several different groups at STRI—including the Smithsonian Bat Lab — as she thinks about how she could pivot her career as a data analyst to help better understand tropical ecosystems.

My grandfather James Karr started this bird survey almost 50 years ago with several other scientists,” Erin Kennelly said, “It seems very full circle to experience something that he started.”

Even though bats have been a major research focus at STRI for nearly a century, most studies have targeted specific species or groups. To date, there has been no systematic, repeated monitoring effort of an entire bat community at STRI. So, inspired by the biannual bird census now led by Corey Tarwater, Rachel Page and long-term bat colleague and STRI Research Associate Marco Tschapka, decided to start a systematic bat survey, sampling the same field sites at the same times of year as the bird team.

The advantage of paired biannual surveys is practical and strategic. The bird team uses mistnets to sample the birds during the day, the bat team can use the same mistnet lanes to net bats during the night. Mirroring methods established by the bird team nearly half a century ago, the bat survey will be performed twice a year, once during the dry season in March, and once during the wet season in July. The bat survey will additionally include three field sites on Barro Colorado Island, to allow for island and mainland comparisons. To complement data from the mistnet captures, both the bat and bird teams will use acoustic monitoring to record bat echolocation calls and bird vocalizations. Aerial insectivores – bats that capture insects flying in the open air – are rarely caught in mistnets. But their echolocation calls are species-specific. The bat team can determine which species of aerial insectivores are flying in the area by analyzing their echolocation calls. Likewise, primarily only understory birds are captured in mistnets, but the whole community of birds can be captured by using their species-specific vocalizations.  

Acoustic surveys will be coupled with data from MothBoxes designed by Digital Naturalism Laboratories (DinaLab). The MothBox is an open-source device that attracts nocturnal insects by LED light and automatically takes photographs at set intervals throughout the night. AI tools can then be used to identify and quantify the insects in the photographs, which will allow the bat team to quantify food resources for the bats. Brianna Johns, a Fulbright researcher with DinaLab, explains that MothBoxes are inexpensive, lightweight, and easy to use in the field, and have a battery that lasts for several days.

“We're really excited to collaborate with the bat team on this project,” Corey said, “By working with them, we can figure out whether or not bats are responding the same way to changes in climate that we're seeing with the birds. We are especially interested in whether we see similar responses between bats and birds that eat similar foods. For example, if we see that insectivorous bats are being impacted the most by changes in climate like we see for the birds, that adds support to the idea that their prey, the insects, are changing.”

By simultaneously studying bats and birds, researchers can monitor how these two groups—both of which have evolved flight and rely on similar resources, yet in distinct ways and at different times—respond to our changing environment. Such studies open the door to discovering new species and behaviors and play a crucial role in shaping future conservation strategies for tropical forests.

Aves de día, murciélagos de noche / Birds by day, bats by night.

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Elisabeth King | Read More

As Communications Manager at the Smithsonian Tropical Research Institute (STRI) in Panama, Elisabeth King bridges the gap between research scientists and diverse audiences. She writes about science, creates exhibitions and video scripts in English and Spanish, making STRI research available to all audiences from school kids to ambassadors.

Rosannette Quesada Hidalgo | Read More

Rosannette Quesada H. is an enthusiastic behavioral ecologist based in Panama City, Panama. She is also a science storyteller and the founder of the science communication initiative Opilio Tracker, a project promoting appreciation for arachnids.