Purple Martins (Progne subis) are highly social birds. After leaving the nesting colony and the care of the Purple Martin landlord, they form large, communal roosts where they sleep at night prior to and during migration. They also form communal roosts on their South American wintering grounds, often with other martin species.

Migratory Purple Martin roosts are typically associated with larger water bodies. Reed beds or dry islands with low, thick brush are commonly used as roost sites. Chosen roost sites usually provide sanctuary from predators and a micro-environment warmer and less windy than land roosts which sometimes form in clumps of trees in urban and suburban settings. Martins also roost on man-made structures, particularly bridges over water and on pipes and girders of petroleum refineries. Winter roosts in South America usually occur in urban settings, often in small parks.

Scores of martin roosts are thought to exist in the eastern half of North America, and some can be very large. It was estimated that one roost at Lake Murray, South Carolina, U.S.A. contained 703,000 martins. Although this is exceptional, many martin roosts are large enough to be detected by Doppler radar. As the martins leave the roost in early morning, going in all compass directions to forage for the day, their synchronous departures show as distinct rings on radar maps. The same phenomenon occurs in South America as martins depart roost sites in South America each morning, however the numbers and locations of martin roosts in South America are not well documented.

Banding studies indicate that martins using a particular roost may come from a wide geographic area. Individual martins may use a roost for several weeks before migrating, but the roost itself may last 8-12 weeks or more. Once established, martin roosts may be reused for many consecutive years.


Migratory and wintering roosts are critically important to the annual life cycle and ecology of Purple Martins. Roosts occurring in natural areas such as reed beds or on dry islands seldom pose problems and often are unnoticed or ignored. However, roosts that form in trees in urban and suburban areas, and roosts that occur on man-made structures sometimes have problems associated with them. This is because they may be perceived as a nuisance to municipalities and owners of private property, or they may be hazardous to the birds or humans. In an example of the latter case, the once hazardous roost at Lake Pontchartrain, Louisiana, U.S.A. achieved some notoriety before conservationists and transportation authorities cooperated to install fencing that prevented martins from colliding with vehicles. Similar but unresolved situations exist in other parts of the country with the one at Umstead Bridge, Mann’s Harbor, North Carolina, U.S.A. being the prime example.

On the positive side, martin roosts can be quite spectacular with tens of thousands of birds descending to roost at dusk. Visiting a roost is a unique bird watching experience, and roosts can provide communities and conservation groups a focal point for environmental education programs, birding festivals or ecotourism promotions.

Regardless of their location or associated problems and opportunities, Purple Martin roosts need recognition and protection. Project MartinRoost is designed to provide that.


The first step in conserving Purple Martin roosts is documenting their occurrence. Based on PMCA’s exhaustive review of Doppler radar images, more than 300 possible migratory roosts are thought to occur in the eastern U.S. and Canada. Little radar research has been conducted outside of the U.S., so how many roosts might exist in South America is currently unknown. Most roosts are undocumented. This is where you can help the most.

Helping is easy. Start by clicking a state, province or country on the map to see if there are any roosts reported in your area. This will take you to the page for that state/province. Since we are just beginning Project MartinRoost, most of the roosts are still undocumented. We hope you will consider locating roosts and report any you find. To see if there is roost in any country in North, Central, or South America, use the map below, dropdown menus below (requires Java) or the roost sitemap to navigate.

In the event that the roost has already been documented, your additional report is still useful! We hope that we will receive at least one report per year for each roost. If you know of a roost that is not listed on this site, your report would be especially helpful!


If you are entering in a report on a PC please use Internet Explorer. Certain functions may not work on other browsers. To report a roost, first determine if the roost has been located already using this website. Many roosts in North America were located by radar and do not have precise coordinates. If you locate a roost approximately 20 miles or less from "radar located" roost, consider the possibility of them being the same roost. If you are near a national or state/province border, check the neighboring region page as well. If you questions or comments, please let us know by using the contact webmaster form.

If you are sure that you have found a roost that has not been located/reported yet, please submit a new roost report here.


Numerous benefits are expected from Project MartinRoost. Detailed information will be available for conservation plans designed to protect roosts. More prominent roosts may serve as focal points for educational events, or one of the ever more popular and common birding festivals. People who simply wish to enjoy a spectacular birding experience will be able to locate and visit a roost in their area. Purple Martin landlords will benefit from knowing that, after leaving the colony, their birds are still being watched over at a roost. Ultimately, Purple Martins will benefit from a better educated public and the sustained recognition and protection of martin roosts.


On behalf of Purple Martins, Purple Martin Landlords, and Bird Watchers everywhere, thank you for your interest in Project MartinRoost.


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