by Anna Morris
Lead Environmental Educator
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| American Robin eggs! |
I am often floored by how quickly the seasons go by, from our brief spring in Vermont, to the flurry of autumn colors. But what I find even more impressive is the speed of the full nesting cycle of our native songbirds. Despite this season’s length—our first Eastern Bluebirds were checking out the meadow boxes on March 2nd, and the last American Robins made their great leap skyward on August 26th—the lifespan of a single nesting attempt is surprisingly brief. The average incubation period for the songbirds we commonly see is just two weeks, and the average length of the brooding period, or time from hatching to when the babies leave the nest, is just 17 days. The whole cycle for one nest is over in a single month.
Due to this relatively short time commitment for one clutch, multiple clutches are not uncommon. As with last year, our resident Eastern Bluebird family raised two sets of five young in one of our meadow boxes, one right after the other. Several pairs of American Robins, never to be one-upped, raised three or even four clutches in a row. That last family of robins fledged on August 26th, having raised three clutches out of the same nest since beginning the season over three months prior, on May 15th. But this was long after the Tree Swallows were done, the last of their young fledging in mid-July.
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| American Robins, just a few days old |
A lot of the difference in this timing has to do with the types of food available to a growing family, and how abundant that food is at different times of the year. For aerial insectivores like Tree Swallows, who grab flies and other insects right out of the sky, that food source has a peak, and quickly tapers off as the weather cools, requiring them to migrate to follow the abundance. American Robins, by contrast, can subsist on a variety of ground-dwelling insects, as well as berries, which are available much later into the summer and fall.
How do we learn this about our local species? Through the citizen science project NestWatch, run by the Cornell Lab of Ornithology, the staff and volunteers at VINS spent a little time each week checking on some 30 nest sites around the Nature Center. We collected data on the number of eggs, the ages of the hatchlings, and the behavior of the parents and reported this information to the NestWatch website. There, Cornell scientists pool our data with others from thousands of NestWatch volunteers all across the country.
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| Eastern Bluebirds, close to fledging |
VINS is Vermont’s only NestWatch chapter, and we encourage our visitors and members to participate in nest monitoring on their own through training workshops in the spring. Our brave little state could use more data: over half of all the Tree Swallow and American Robin nests monitored this year in Vermont were right here at VINS. Would you like to get involved with citizen science projects at VINS or at home? Do you know of a nest near you? Join the effort! It’s free, and helps contribute to real science. Check out nestwatch.org or contact amorris@vinsweb.org for more information.
We also want to extend a special thank you to Aine and Ian, our stellar Citizen Science Volunteers, who made this very busy summer’s data collection possible. Without their weekly dedication to monitoring our Tree Swallow and Eastern Bluebird nest boxes, we would not have been able to make these vital observations that are aiding our understanding of breeding bird biology.