Migration patterns from two FL birds part of landmark study
Editor’s note: This is the third and final installment in a series about the process of being a purple martin landlord.
In the past, we have discussed ways to attract a colony of purple martins, but because the window for attracting them is short, we did not say anything about why these birds are so special.
The birds are delightful to have around. They seem so cheerful with their near-constant chatter. It’s fun to watch them raise their families from eggs to fledglings in just six weeks.
Whereas you will typically never even find the nests of, say, red-headed woodpeckers or nuthatches, the martins will happily raise their young right out in plain view for you and your children to watch and enjoy. Nest checks every 3-5 days can greatly increase their fledge rate. (Contrary to myth, martins do not mind you handling their babies and they will not “smell human scent” nor abandon their nests as a result.) Thus a martin colony provides a great learning laboratory for children…right in your own backyard.
These birds have become dependent on human-provided housing. With most wildlife, it’s the opposite. Humans tend to deprive most animals of habitat, but with martins it’s a symbiotic relationship. If we didn’t provide man-made nesting cavities, they would become extinct or nearly so.
Their navigation abilities are magical. These birds migrate all the way down to the middle of Brazil…and then return to the very same housing they nested in the year before! No one knows for sure how they do this and, up until a couple of years ago, no one knew the exact path they took.
With regard to the last point, our knowledge just took a quantum leap with the advent of “geo-locators.” No, not GPS; GPS receivers would consume way too much power and not last much further south than Owatonna. Geo-locators are tiny devices that are strapped to the backs of a few birds. They measure sunrise/sunset times and compare them to an onboard clock thus estimating location to within a few dozen miles.
It just so happens that two of the martins in my own colony (on the southwest shore of Forest Lake No. 2) returned with their precious cargos this summer. I was able to trap them, remove the devices, send them to Dr. Bridget Stutchbury of York University in Toronto for analysis and, as of July 8, I received the results back!
Up until this summer, we knew the routes of purple martins from Pennsylvania but never Minnesota. One of my two “Forest Lake” birds (No. 17070, an adult female pictured just before I removed the geo-locator) went the “normal route” down to Louisiana, across the gulf to the Yucatan, and then on down through Central America to its wintering grounds in Brazil. But the other martin (No. 17067, an adult male) surprised us all. He opted for Milwaukee, Miami and then Cuba before cutting over to Panama!
We have known about roosts of 50,000 to 100,000 martins gathering in late August in Minnesota (last year near Avon). In fact a banded bird from my colony in Forest Lake was sighted at the 2010 roost near Osakis. One has to wonder: What would drive a martin to fly northwest of Forest Lake, linger there for a couple weeks and then head south to Louisiana or Texas en masse?
Now that we know No. 17067 lingered near Milwaukee for 11 days, we have asked our Wisconsin neighbors to be on the lookout for another roost in their state! Anyway, after he crossed the Gulf of Mexico, he then lingered another six days near Camagüey in Cuba before dashing to an area near the border between Costa Rica and Panama. But once he made it to Colombia, he took his time going the rest of the way to central Brazil, as you can see by looking at the dates on the map.
In summary, I enjoy purple martins because they like to be near humans, they eat flying insects by the thousands, and as if by magic, they make the 9,400-mile-round-trip to Brazil and return to the very same house they departed some seven months earlier!
Lee Bakewell is a bird enthusiast who lives on Forest Lake. Much more information can be found on purple martins at www.purplemartin.org. Feel free to contact Bakewell with questions at [email protected] or (651) 451-8481.