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A snapshot of BECO's 2016 field season
Summer is winding down and our field activities are complete for the year. Here's a brief look at some of the work we did this summer.
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A Bobolink nest built on the ground in a cattle pasture.
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Monitoring Bobolink in rotationally grazed pastures
For the second time in ten minutes, Gerald sees a female Bobolink with food in her mouth, flying toward the middle of the pasture. He stays as still as possible, crouched in the grass, watching through binoculars as the female hops among the tall June grasses. The bird disappears out of sight and a few grasses move as she runs along the ground to her nest, delivering the green caterpillar to her hungry nestlings. As she leaves in search of more food, Gerald gets the final clues he needs to find the nest. He approaches carefully and gently pushes the grass aside to reveal 5 young Bobolink in a small cup-shaped nest.
Gerald and the rest of the BECO crew monitored nearly 90 Bobolink territories in rotationally grazed cattle pastures on several farms in the Ottawa Valley during May, June, and July. Despite the impressive efforts of Bobolink parents to hide their nests, we found and monitored 32 nests throughout the season. The goal of this project is to assess if strategically placed Bobolink refuges - areas that aren't grazed by cattle during the nesting season - can have a meaningful impact on conservation efforts for this species.
Fifteen of the 32 nests we monitored in grazed pastures and refuges fledged young; the others were predated or destroyed by cattle trampling. Now our task is to start looking at the data we collected in the first year of this two-year study, a collaboration with the Ontario Soil and Crop Improvement Association. These data will help us to learn more about how cattle affect the Bobolink that breed in their pastures and if small nesting refuges in rotationally grazed pastures are an effective conservation strategy.
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Gerald Morris, Grassland Bird Field Assistant, watches for signs of Bobolink nesting activity.
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Tracking Bobolink dispersal using radio telemetry
We also spent a lot of time watching Bobolink in Simcoe County this year, where we conducted our pilot radio telemetry project. For this project, we used radio transmitters to track the movements of Bobolink after the hay harvest displaced them from breeding areas. We wanted to see where the birds went and if they attempted to nest again.
Before attaching the transmitters, we had to catch the birds, which is not a simple task. We had a small window of opportunity to capture birds in early June, before the hay was cut. To do this, we relied on their territorial nature. By setting up speakers on either side of a net placed near a nest, we were able to mimic the presence of another singing Bobolink and create the illusion that this bird was moving from one side of the net to the other. When the technique worked, the bird we were attempting to catch would fly into the net in pursuit of the phantom bird invading its territory. Mostly, this works on males, who are more territorial and respond more readily to the broadcasted song of another male, but we found that females sometimes responded when we played various call notes. Unfortunately, this trick doesn’t always work, and we sometimes ended up with an empty net.
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Zoé Lebrun-Southcott, ED and Wildlife Biologist, attaches a small backpack radio transmitter to a male Bobolink.
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We captured 8 Bobolink in two hay fields in Simcoe County; 5 received small backpack radio transmitters. When the farmers cut the hay necessary to feed their animals, these birds' nests were destroyed.
Using handheld antennae, we attempted to track the movements of the tagged birds following the harvest, to see how they responded and where they went. Some of the birds disappeared within a few days and we were unable to re-locate them within our search area, while others we tracked for more than 40 days after the harvest. These birds did not re-nest, but spent their time loafing in uncut hay fields and fallow fields nearby, where other Bobolink were still nesting.
The overlap of the timing of the hay harvest with the Bobolink nesting season is a true conservation challenge. Most Bobolink aren't finished nesting until July, and many farmers need to cut their hay in June to provide their animals with nutritious hay throughout the winter. With this project, we wanted to begin investigating how Bobolink respond to the harvest. More information about how the birds are affected can lead to better conservation and stewardship practices that also work with farming practices.
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Andrew Campomizzi, Research Scientist, releases a male Bobolink with a radio transmitter.
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More work on Barn Swallows and social cues
This year we continued our investigation of the influence of social cues on Barn Swallow nesting and behaviour at new nesting structures. Our results from the 2014-2015 study we conducted in collaboration with Bird Studies Canada indicated that social cues (decoys and vocalizations) did not increase nesting at new nesting structures in the same year; however, we did see an impact on the behaviour of the birds. This piqued our curiosity and we wanted to continue the social cues work in 2016 to see if more birds would nest in the structures in the next breeding season, and to more closely investigate the behavioural response to the social cues.
Nesting results in 2016 were disappointing. Several of the structures built and treated with social cues in 2015 were again not used by the birds in 2016. Additional broadcasts of vocalizations at 3 of the sites this year did not result in nesting at these sites. Although these results are discouraging, the information this research provides is important because many organizations are building similar structures to mitigate the loss of nesting habitat. Evaluating the effectiveness of this strategy to preserve nesting habitat for this species is an important step toward evidence-based conservation.
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A Barn Swallow structure built in 2015 for the social cues experiment.
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Thanks
None of this work could have been accomplished without our amazing field staff and volunteers, our supporters, and of course the generous landowners who allow us to conduct these research projects on their properties. Thank you!
Support for BECO's 2016 field projects was provided by the Ontario Trillium Foundation, the Government of Ontario, the Ontario Soil and Crop Improvement Association, Colleges and Institutes Canada, Mitacs, Vortex Canada, and individual donations.
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