Bird calls and songs are giving scientists new insights into avian behaviour and population patterns. How researchers are gathering information for the third Ontario Breeding Bird Atlas by listening
A single sharp note of a birdsong stops Mike Cadman in his tracks.
“That’s a rose-breasted grosbeak,” he says, pointing to the branches overhead, as that first piercing note is followed by a tumble of cheery, melodious tones. “Right there.”
It is not the only bird singing within earshot, but for a moment it stands out.
“Nice,” says Cadman quietly, as he looks down at his phone and taps in the ID.
After a lull, the grosbeak starts up again. “That one,” Cadman says, helping me link the song to the unseen bird. “It sounds like a robin that’s had singing lessons.”
Above: Mike Cadman scopes out birds along the Speed River in Guelph. Below: Rose-breasted grosbeak
The rose-breasted grosbeak is a common bird. The reason it caught Cadman’s attention is that we had not yet heard from the species on this morning’s walk along the banks of the Speed River, outside Guelph. This is one of the first days of data gathering for the latest edition of the Ontario Breeding Bird Atlas and Cadman is doing his part, recording each species and the number of birds that we encounter along our route, plus any evidence of breeding activity—nests, for example, or adults carrying food—in an atlas checklist. This section of river is within a 10-by-10-kilometre square for which Cadman has volunteered to collect at least 20 hours of data. The data collection involves checklists as well as timed “point counts” at 25 prescribed locations in which a surveyor tallies all the birds they see or hear in a five-minute span.
The atlas survey, conducted every 20 years over a five-year period, is a seminal project critical for scientific understanding of bird population trends and broader conservation planning. Ontario Nature is one of five core partners, along with Birds Canada, Ontario Field Ornithologists, the Ministry of Natural Resources and Forestry, and Environment and Climate Change Canada. Organizers divide the province into a grid of squares like Cadman’s; in each, participants (mostly volunteers) follow the same checklist and point count protocol to record the presence, abundance and breeding evidence for every species they observe.
Cadman, a biologist with the Canadian Wildlife Service, also happens to be the atlas coordinator, a role he has held for all three surveys to date, starting in 1981. While most people appreciate bird sounds, and many can identify a few birds from their songs, only observers with well-honed talent and knowledge can apply it in data gathering.
Cadman began his birding adventures using Roger Tory Peterson field guides, the first popular illustrated field guides created by the American ornithologist. Cadman also spent a lot of time listening to recordings and studying mnemonics, which liken bird songs and calls to memorable human words and phrases. In time, each song began to find “a little place to fit in my brain,” he says.
With the atlas’ third edition, however, experts like Cadman are getting some help from new recording technology, both hand-held (photo, right) and autonomous. The aim is to improve the amount and coverage of the data collected, particularly in roadless areas in the north, and to build an audio archive to support future research. In this, the atlas mirrors broader trends in bird study.
“Sound is being used more and more as part of ornithology, in a variety of formats,” says Mark Peck, manager of the Royal Ontario Museum’s Schad Gallery of Biodiversity and program director for the Toronto Ornithological Club. In the process, scientists are learning more about bird sounds, and about the birds themselves from the study of those sounds.
THE NEW ATLAS HAS EVOLVED a great deal since the second edition. Technology—mapping and data sharing, as well as audio and video—has changed enormously in the past 20 years. The scale and reach of Internet platforms have exploded, while phone and app development has transformed birding resources and made sound and video tools accessible to all.
The checklist Cadman compiled on our morning walk, for example, is modelled on eBird, the online platform for birders worldwide. It is incorporated in a custom app called NatureCounts that was developed for the atlas’ third edition. Data collection for the second atlas was based strictly on handwritten notes and data forms at the level of the 10-km square, but the app’s development has made site-based checklist surveys possible for the third edition. “The app tracks where people are in the field, so it has great potential in relating birds to their habitats and gives us a better idea of how many birds are out there,” says Cadman.
Widespread use of audio recording in ornithology to capture and analyze the full range of avian songs and calls (see sidebar) has also gained significant steam. “Human point counts are great, but they have two major limitations,” says Erin Bayne, a biology professor at the University of Alberta and one of Canada’s foremost experts in wildlife sound monitoring. “The first is that people can’t be everywhere all the time. And number two, no matter how good someone thinks they are, birds are tricky animals to identify by sound, [so recordings can be a backstop].” They also enable consistency in measurement of amplitude, which is correlated with distance. People are not as consistent.
Up until about 2013, recording involved people walking around with microphones. Then came the first decent, affordable commercial recorders using batteries, programmable timers and memory cards of high enough quality to be left outdoors for weeks or months. “That changed our ability to sample anything that makes a sound,” says Bayne, who has created the largest Canadian archive of bird, amphibian and mammal recordings—WildTrax—used not only by academics but also governments, industry and conservation organizations. Researchers could now do surveys any time of day or season by going to a spot only twice: to set up the unit and later to pick it up.
Recorded data, whether it is gathered manually or autonomously, provides typical metrics such as species counts and abundance, but it also opens many avenues of study based on elements such as when the birds are calling and when they are silent, how songs and dialects are changing over time, and the interplay between different species.
A recent example of the latter stems from work by scientists at the University of Windsor, who analyzed flight calls made by different species of migratory birds travelling at night. The researchers were surprised to learn that calls were more alike among species sharing the same migration routes and timing—suggesting cross-species communication in flight plays a role in their migration.
In another study, one of Bayne’s students placed autonomous recorders in areas of the western boreal forest to determine the exact timing of different bird species’ migration and the start of breeding season. “Because we have the recording devices turned on, we know literally to the second when the first birds arrive and start singing at a site,” says Bayne. “A bird [males mainly] spends a lot its time singing once it sets up a territory, so you can tell it’s stopped and is staying there.”
ANATOMY OF BIRD SOUNDS
Bird vocalizations take many forms. In general, however, they fall into two categories: songs and calls.
Songs: People might think all birds sing. In reality, only about half of all birds are song- birds. That designation is the result of an anatomical feature—a specialized voice box that enables some species to perform complex songs. Bird songs tend to be longer than calls and to have clear patterns that can be recognized. Usually, male birds do the sing- ing, at least in the northern hemisphere, and bird song is most prevalent during breeding season as a way for birds to designate their territory and attract mates.
Calls: Almost every bird produces calls, and they can be heard year-round. Usually shorter and simpler than songs, calls are often just a single syllable and generally are produced by both females and males. Most species use a variety of calls to communicate different messages. Contact calls are ways for birds to keep in touch with one another, but there are also alarm calls and in-flight calls. Young birds utter begging, or demanding, calls when they want to eat.
Sonograms (below) show distinctive patterns of every bird’s songs and calls.
Another area of recent research involves the impact of human noise on bird abundance and behaviour. Can singing males communicate effectively with females and other males, for example, when artificial noise is a constant? Bayne and his students looked at this issue in areas afflicted by noise from oil and gas development. Results suggest that the constant loud noise from compressors and other equipment leads to reduced abundance and lower reproductive success. Elsewhere, studies focused on traffic and urban noises have found that some species—such as eastern wood-pewees and white-crowned sparrows—alter the frequencies or length of their songs in order to be better heard.
BIRDS CHANGING THEIR tune was the subject of a celebrated recent study involving the iconic song of the white-throated sparrow. Common across much of the boreal region and most of Ontario in summer, the sparrow’s song is described mnemonically by many in this country as “Oh-my-sweet-Canada-Canada-Canada-Canada.” But last year, Ken Otter, a biology professor at the University of Northern British Columbia, published a paper that revealed that many white-throated sparrows had, for reasons unknown, dropped a few syllables, adapting the mnemonic to “Oh-my-sweet Cana-Cana-Cana-da.” What’s more, by analyzing recordings from across the country, Otter showed that while the new dialect originated in the west, sparrows farther east are picking it up.
The fact that Otter’s findings were possible only because he had access to recordings in sound archives underscores the long-term value of these audio storehouses. To Emma Horrigan, Ontario Nature’s conservation projects and education manager, this is one of the most exciting aspects of the expanded use of bird sound recordings for the atlas. “In addition to supporting the collection of data about breeding birds themselves, there are just so many untapped potential research projects that could come out of this information,” she says.
Cadman is looking forward to listening to the recordings from spring and summer on snowy days in December. But right now, there is time for one more lesson in birding by ear as we circle back toward our starting point by way of a large grassy field.
The elusive Bobolink
Earlier, we had been talking about bobolinks—black-and-white ground-nesting birds that are declining in Ontario, especially where farmers cut their hay early, before the bobolink young have left the nest. I have only seen one in the three years since I moved from the city to a home in the country, I told Cadman. Now, he points at a black bird rising and falling over the grass in the distance.
“Here’s a bobolink. Just landed in the grass in front of that lone telephone pole. You can just see his head poking up.”
I struggle to see it. A few seconds pass. “Now it’s calling,” he says.
“That almost electronic sound?” I ask. “That’s the bobolink?”
“Yeah. It’s an R2-D2 kind of thing.”
The realization hits me immediately: I hear that sound almost every day from across the road from where I live. The elusive bobolink is not so elusive after all. I just need to be a better listener.
This article was originally published in Ontario Nature’s Fall 2021 ON Nature magazine. Photos: Mike Cadman is my photo; Rose-breasted grosbeak courtesy of pixabay.com/TheSOARnet; Bobolink courtesy of pixabay.com/jasonjdking. Sonogram image courtesy of Cornell University Guide to Bird Sounds.