What is a Roost? In late summer after leaving the nesting colony, Purple Martins gather in large flocks to feed, socialize, and rest before migrating down to South America. This activity, known as migratory roosting, can attract thousands of birds to one small area. Martins also form winter roosts on their South American wintering grounds where they will often flock together with other martin species. Often roost will form on Doppler radar in the form of a ring or crescent or even a large mass of dots. The best time to view the images is between 8-10 UTC or MT. The header image shows these roost rings in Canada and the US. The doughnut shape is located at Point Pelee National Park.
Where to Find a Roost?
Typically migratory roosts are found;
* in larger bodies of water—reed beds and dry islands with low thick brush provide sanctuary from predators and a micro-climate warmer and less windy than land
* in urban and suburban areas roots can be found in trees or man-made structures such as bridges and pipes
* winter roosts in South American can occur in urban settings—often in small parks and in the Amazon rainforest.
There are many migratory roosts scattered around North America and some can be very large. Some roosts may contain hundreds of thousands of martins. Many martin roosts are large enough to be detected by weather radar. 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 until all birds are gone. Once established, martin roost locations 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 can be a spectacular sight with tens or even hundreds of thousands of birds descending at dusk. Visiting a roost is a unique experience, and roosts can provide community and conservation groups a focal point for environmental education programs, birding festivals, or ecotourism promotions.
How You Can Help: Project Martin Roost is a cooperative research project between the Purple Martin Conservation Association, its members, and bird enthusiasts everywhere, designed to protect and promote Purple Martin roosts in North and South America.
Nature Canada has joined forces with the public to locate roosts in Canada and asks everyone who finds a swallow roost to contact them.
The first step in conserving Purple Martin roosts is documenting their occurrence. Radar images suggest that more than 350 migratory roosts occur in the eastern U.S. and Canada; however most of these locations are undocumented. Where exactly are these roost sites? How many exist in North and South America? Are there any issues with established roost sites? This is where you can help the most!
Where do they go after they leave the roost?
The PMCA has produced an excellent video found on YouTube following the voyage of Purple Martins from 2011-2014.
Check it out:
Journey South and Back: https://www.youtube.com/watch?v=vMPxlXuukIg&app=desktop