If you’ve ever seen a Purple Martin in the eastern United States, you likely saw them nesting in human-made birdhouses. But here in southern Arizona, we have a subspecies with a different lifestyle: the Desert Purple Martin. Unlike their eastern relatives, these desert specialists look slightly different, migrate later, and refuse to live in human structures. Instead, they nest exclusively in cavities of giant columnar cacti, like Saguaros and Cardóns.
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| A pair of Desert Purple Martins on a Saguaro at Davis-Monthan Air Force Base |
For years, details about their movements and migration remained a mystery. But thanks to new tracking technology, that’s beginning to change. Jennie MacFarland of the
Tucson Bird Alliance has been working to shed light on Desert Purple Martin migration, and this year, thanks to support from the Davis-Monthan Air Force Base, I had the opportunity to contribute to this goal. In collaboration with Jennie and others, we set out to answer the question:
Where do Desert Purple Martins spend the winter? Early data suggested they might cross paths with the eastern subspecies to winter in eastern Brazil, but this was based on just a couple of birds.
Last month, I joined Jennie, Tori Wiley (Northern Arizona University / GoneBirdin.com), and Joe Siegrist (Purple Martin Conservation Association) on the ground in Tucson. Together, we captured 26 Desert Purple Martins and fitted them with tiny satellite trackers, each weighing less than a dime.
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| Removing a Desert Purple Martin from a mist net. (Photo by George Andrejko) |
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| Joe Siegrist and Tori Wiley attach a satellite tracker to a Purple Martin |
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| A Purple Martin with its newly-applied satellite tracker |
The data started coming in almost immediately—and the results are already giving us crucial conservation insights. While nesting, adults use a variety of communal roosts in the region, including at some unknown locations high in the nearby mountains. As the birds have started to move south for the winter across Sonora, each martin has spent its nights in coastal mangroves, highlighting how critical these mangroves are as stopover habitats.
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| Brightly colored lines show the location of four Desert Purple Martins, three heading south to the coast of Sonora, and one still in the Tucson area which will likely be migrating soon. |
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| In a mangrove-filled estuary of coastal Mexico, Desert Purple Martins return to roost every night as they stop to refuel on their migration south |
Last week, I got to see this in person while vacationing in a village north of Bahía Kino, Sonora. The landscape was dotted with Cardón cacti, providing prime nesting habitat for Desert Purple Martins. As evening fell, dozens of martins gathered along nearby highway power lines. A year ago, where those birds roosted for the night would have been a guess. But thanks to our newly tracked birds, we now believe they were heading to sleep in the nearby mangroves. Soon these martins, too, would likely join the rest of their subspecies for the long trek to winter in the Amazon Basin of Brazil.
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| A few of over 80 Purple Martins we spotted along a wire near a mangrove estuary just north of Bahía Kino, Sonora. |
Stay tuned as we continue to follow these incredible travelers on their journey south!
