One of the keys to the success of the Northeast Regional Migration Monitoring Network will be the combination of research techniques. Network researchers are banding birds, analyzing biological materials, operating surveillance radar and conducting visual surveys in an effort to document how songbird species are using the Gulf of Maine as they migrate through the region.
Acoustic surveying is another critical research technique that will add important layers to the network researchers’ findings.
Migrating birds call to each other with brief chirps or “zeets” of various frequencies. Network researchers such as UMaine biologist Rebecca Holberton have set up arrays of acoustic recording equipment throughout the Gulf of Maine region to pick up the birds’ sounds and determine what species are flying overhead.
The microphones convert the birds’ sounds into an electric signal. A Cornell University sound analysis program called Raven translates each signal into pixels to generate a visual spectrogram image. To determine the species represented in a spectrogram, the image is compared to a set of known-species spectrograms based on the frequency range and the pattern of notes the birds make.
A group of undergraduates in Holberton’s Lab of Avian Biology is harvesting spectrograms from several hundred sound files. So far, they’ve found a number of species, including songbirds, shorebirds, seabirds, owls, some amphibians, and even a few animals, such as coyotes, foxes and the occasional domestic sheep and horse.
One listed by federal and state government as a species of concern is the Canada warbler, which is normally very secretive and not easily seen or often captured by bird banders. However, acoustic survey methods have detected this species as it migrates through the region, providing important baseline data needed to help track any change in its numbers as its primary breeding habitat, the boreal forest, experiences threats from global climate change.
“The acoustics are another way of getting at which species are in a given area,” says Wes Wright, a UMaine assistant scientist who helps run Holberton’s lab and has been overseeing the undergraduate acoustic research group. “Banding birds during the day is not quite representative of what’s migrating overhead at night.”
UMaine student Christina Hassett, an ecology and environmental sciences major with a concentration in natural history, got involved in the research in order to delve into practical applications of ornithology.
Hassett spent some time this year compiling statistics from acoustic arrays located on Petit Manan Point and Metinic Island in order to present a poster of the undergraduate group’s work at UMaine’s Undergraduate Research Symposium. The goal of the poster is to gain insight into whether songbirds travel in specific geo-spatial patterns. This information is key to determining which habitats may be important to migratory birds and how to protect them.
“It’s interesting being involved in the analytical aspect of scientific research,” says Hassett, who is from Yarmouth. “You find that trying to gain significant insights using your data is simply not a cut-and-dried science. There’s a lot of trial-and-error involved in coming out with solid results.”
Ashley Kolofsky, a zoology major from Rutland, Mass., said her participation in the acoustics research has her re-thinking how she wants to use her degree.
“When I decided to major in zoology, I was thinking about working with animals in a zoo,” she says. “But recently I’ve been more interested in doing research and observing wild animals in their natural habitat, which you can’t do in a zoo. I think it would be more interesting to watch them in their own environment.”
You may need to turn up the volume on your speakers to hear some sounds.
View a Spectrogram of the Magnolia Warbler
View a Spectrogram of the Northern Sawwhet Owl
View a Spectrogram of the Canada Warbler
View a Spectrogram of the American Redstart
View a Spectrogram of the Ring-necked Pheasant
View a Spectrogram of the Northern Waterthrush