What happens when you're trying to record birds at night but can't hear anything over the insects? Mennill Lab Postdoctoral Researcher Natalie Sanchez learns she must adapt her bioacoustics setup to overcome a uniquely buggy challenge. Here, she tells us about monitoring migratory and resident birds in the imperiled tropical dry forests of Costa Rica—and the clever deployment strategy she used to record bird calls in one of the noisiest soundscapes on Earth.
Hey, Natalie. What can you tell us about the project you’re working on?
Our current undertaking, supported by a MITACS Accelerate grant, aims to combine state-of-the-art bioacoustic monitoring and tracking technologies to study avian biodiversity and animal movement in the tropical dry forest of northwestern Costa Rica. This includes a parallel focus on birds that migrate between Canada and Costa Rica and birds that reside year-round in the tropical dry forest.
What can be learned or gained by studying this?
Our findings will provide information on the population biology, movement ecology, and behavioral biology of year-round and migratory birds in the world’s largest remnant of tropical dry forests. This is critical because tropical dry forest in Costa Rica is imperiled as it’s easily converted into agricultural land.
Are you working with any others on this?
I work at the Mennill Lab within the Department of Integrative Biology at the University of Windsor, where MITACS supports my postdoctoral research with partner organizations Wildlife Acoustics and Birds Canada. I also work with the nonprofit organization Guanacaste Dry Forest Conservation Fund.
Cool. Where does your fieldwork take place?
Our study focuses on multiple locations in Costa Rica: Santa Rosa National Park and Pitilla Biological Station at Área de Conservación Guanacaste, Guanacaste; Organization for Tropical Studies, San José; and Reserva Bosque Nuboso Santa Elena, Monteverde.
Sounds wild! What species are you monitoring?
We are studying diverse species of migratory birds, including warblers, thrushes, and vireos. I am interested in the vocalizations these birds produce when migrating at night. Ultimately, we hope to expand Motus tracking towers at strategic locations in the Guanacaste Conservation Area to obtain records of migratory birds carrying tracking devices and contribute to the global Motus network of studying animal movement. We are very interested in exploring how recording migratory flight calls can help us expand Motus-based migration tracking.
And what does this look like?
Our project involves monitoring migratory songbirds by collecting nocturnal flight call recordings and conducting bioacoustic surveys of avian biodiversity of birds over the neotropical dry forest during spring and fall migration. We also use ground-level bioacoustic point counts to survey resident birds and stopover migrants in the neotropical dry forest during the migration season.
Whew! That’s a lot. How does bioacoustics help you achieve these goals?
In our lab, we have used bioacoustics to study animal sounds from different perspectives and answer behavioral, ecological, and applied conservation-related questions. Wildlife Acoustics audio recorders allow us to collect acoustic data passively for extended periods at particular times of the day, reducing the interference of human presence in the wild.
What bioacoustics equipment are you using?
I use a lot of Song Meter SM4s and Song Meter Mini acoustic recorders. Other members of the Mennill Lab use Song Meters SM2s and SM3s with integrated GPS to triangulate the position of birds using microphone arrays.
When, where, why, and for how long do you deploy recorders?
From March through May, we deploy Song Meter Mini acoustic recorders, 7 m to 10 m off the ground, with the microphone facing up towards the sky. These recorders are part of a new strategy we are using to reduce insect noise from interfering with the recordings. We call our approach “Song Meter Mini Bucket Microphone for Night Flight Call Recording." See how we do it:
Are there settings you find particularly helpful?
We record birds, especially songbirds, so we found it helpful to deploy with the following settings:
Sample rate: 44,100 Hz
Maximum recording length: 60 min
Channel: left
Left-channel gain: 18 dB
Schedule start time: 16:00 h
Schedule end time: 07:00 h
Duty cycle: Cycle
Duty on: 00:10
Duty off 00:50
We found the duty cycle especially useful. Because we were recording for more than a month, setting short recording periods helped conserve battery life. Our Song Meter Minis were deployed in remote locations and, in most cases, at elevated heights, so frequently replacing batteries would have been costly.
What kinds of recording challenges have you run into?
Nocturnal flight calls are very brief and occur only within specific frequency bins. When we record within tropical forests, we face an intensely loud chorus of insect noise that masks the birds’ calls, making it very difficult to answer our research questions.
This is the opposite of Pura Vida. How did you overcome this?
Dan Mennill, Zack Gayk, and I designed a “Bucket Microphone for Night Flight Call Recording” for the Song Meter Mini recorders to cut down on recording this unwanted noise. It consists of a bucket, a plastic cone (acting as a parabola), and sound-dampening foam. Inside the bucket, a Song Meter Mini is secured at the base, the wall of the bucket is covered with foam, and a cone is placed on the microphone. During the 2023 field season, we detected nocturnal flight calls in our four field sites—the bucket mic worked!
Thanks for sharing, Natalie! How can other researchers learn more about your project?
They can visit my website, tweet me (@Nati_SanchezU), or send me an email!
About Natalie V. Sánchez, PhD
Natalie is a Behavioral Ecologist and Postdoctoral Fellow at the Dan Mennill Lab in the Department of Integrative Biology at the University of Windsor, ON, Canada. A Costa Rican native, Natalie has collaborated with Guanacaste Dry Forest Fund since 2014, teaching parataxonomists how to recognize when migratory birds are calling so they might educate/engage the public to learn more about them, leading to their conservation and the protection of the tropical forest climate they depend on. Her “spark” moment was based on wanting to understand how animals communicate. Previous projects have involved the study of (elusive) Rufous-and-white Wrens in Costa Rica, Lincoln’s Sparrows in Northern Alberta, Canada, and avian response to Pygmy Owl calling in Costa Rica. She is endlessly fascinated by animal communication, tropical birds, and bioacoustics.
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