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Purple Martin Patrol

Purple Martin Patrol

Purple Martins In Nashville

Purple Martin Basics

Purple Martins (Bird Banding Laboratory alpha code PUMA) are the largest swallow species in North America. Adult males are easily distinguished by their dark bellies, a unique feature among North American swallows. Females, on the other hand, exhibit more brown and gray coloring on the back of their heads. These birds breed in North America, marked by their orange hue, and migrate to South America during the winter months, indicated by their blue coloring. Notably, much of the eastern population embarks on a remarkable migration journey across the Gulf of Mexico, covering over 10,000 miles annually. Migration typically commences after nestlings fledge, with peak activity occurring in mid-August here in Tennessee. Purple Martins are aerial insectivores, meaning their diet consists solely of flying insects such as beetles, true bugs, flies, dragonflies, damselflies, leafhoppers, grasshoppers, crickets, butterflies, and moths. They are often observed foraging at altitudes of at least 50 meters. Unlike many other bird species, Purple Martins heavily rely on human-made nesting sites, such as martin boxes or gourd systems, a behavior shared with Chimney Swifts and Barn Swallows. While historically nesting in woodpecker holes and snags, they now tend to nest in colonies. Typically, Purple Martins produce only one clutch of young per breeding season, with an average of 3 to 6 eggs per clutch. The young leave the nest at approximately 28 to 29 days old. Purple Martins are known for their vocal nature, with at least 11 distinct vocalizations identified. Unfortunately, breeding bird survey (BBS) data suggests that populations of Purple Martins in North America have been experiencing a long-term decline, a trend that has been particularly pronounced since 1980.

History of PUMA fall migration roosts in Nashville

Before and during migration, Purple Martins gather in large night roosts, which typically last 8-12 weeks or longer. Individual martins may utilize a roost for several weeks before continuing their migration journey.

Since 1996, the Purple Martin Conservation Association (PMCA) has detected significant numbers of martins roosting in two locations within the Nashville area, using NEXRAD (radar) images. These roosts have been consistently documented over the years, with fluctuations in the number of martins observed. Notably, the largest roost was observed from 2020 to 2022, with an estimated 150,000 martins. It’s worth mentioning that the roost location has changed multiple times over the years.

Research at Nashville Metro Parks, Warner Park Nature Center (WPNC)

Since 2000, WPNC staff have diligently monitored the breeding success of Purple Martins at the gourd system on the nature center campus, alongside federally permitted researchers banding over 700 nestlings to date. Notably, nestlings have also been banded at Shelby Bottoms Nature Center. In 2021, pioneering radio-tagging efforts unveiled that PUMAs from WPNC typically spend about a week in their nesting area post-fledgling before congregating at the downtown roost, prior to embarking on migrations to South America. 

In 2022, nestlings were radio-tagged at WPNC, Bells Bend Nature Center, and Ellington Agriculture Center, revealing their extensive use of Middle Tennessee for foraging, with one tagged individual even detected in Costa Rica during migration. Remarkably, a returning nestling to WPNC in 2023 and another detected in Pennsylvania underscore the significance of these tagging efforts. Looking ahead, with 25 PUMAs radio-tagged in 2023 across various locations, WPNC eagerly anticipates uncovering further insights into their post-fledgling movements and roost behavior.

How To Help

  • Purple Martins depend on artificial nests to breed, so install a gourd system. The PMCA has fabulous resources.
  • They only eat insects – grow native plants and do not use pesticides! Encourage others to do the same.
  • Volunteer to educate and engage at the roost location.
  • Visit Bird Safe Nashville to learn more.
  • Contact your local representative to let them know we should welcome these extraordinary travelers by passing bird-friendly window laws.
  • Restricting the use of pesticides.
  • Ensuring the roost location is safe for the birds and they will not be disturbed.
  • Help join Nashville’s Urban Bird Treaty efforts to protect bird habitat, reduce hazards to birds, and educate the public about the benefits of birds. 
  • Contribute to the BIRD Programs research by donating to Friends of Warner Parks.

Resources

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