Coming Home to Roost

A video of Purple Martins recently taken in Austin, Texas, by Friends member George Mason and  posted on Facebook sparked some questions about the huge numbers seen. Purple Martins will soon begin their journey to their wintering grounds in Brazil. In the meantime they have been gathering at roosts across the country after completing the nesting season. “A martin roost is a place where Purple Martins sleep at night. A martin roost typically forms annually with martins using it nightly during late June, July, August, and early September in North America…. A martin roost may have from 1000 to 1,000,000 individuals, with numbers more typically in the 25,000 to 100,000 range. Most martin roosts are large enough to show up on Doppler weather radar as the birds leave in the morning.

Purple Martins heading to roost in Austin, Texas, by George Mason

Closer to home, after a great start on nesting at this year at Hagerman National Wildlife Refuge, the Martins seem to have left prematurely; did they move to a roost? On June 11, Refuge Manager, Kathy Whaley, Noted “We have not seen activity in more than 2 weeks now at the martin house. When we checked it today and we found 11 of the 14 compartments had been occupied by martins and had a nest. Two compartment inserts had been turned around as they had house sparrow activity for several weeks in a row. One compartment had a house sparrow nest. We are not sure why the birds left their nests, leaving 11 unhatched martin eggs and 4 martin baby bird skeletons in one compartment. I hope they try again next year.”

Perhaps the persistent spring/early summer rains were the culprit. According to PurpleMartin.org, “Since martins feed solely on flying insects, they are extremely vulnerable to weather conditions that affect insect availability. Prolonged bad weather, such as rain, snow, cool temperatures, and/or heavy winds, all reduce or eliminate insect flight. If poor weather persists for more than 2 or 3 days, martins begin to die of starvation. 

Jack Chiles has reported seeing anywhere from 3 - 11 on the weekly bird census, which has been restricted to the perimeter of the Refuge due to flooding.

We found more about roosts in “Preparation for Migration”:

"Migration is an extraordinary act that requires a lot of energy and endurance. In order to accomplish their goal of returning to their summer or winter homes, birds must have an excellent source of energy to rely on. Martins, like all migrants, consume energy-rich foods just prior to migration and develop fat stores. Fat provides two times more energy than either carbohydrates or proteins. The amount of fat each species accumulates determines how far a bird can fly nonstop.

A second preparation for migration is that of forming roosts. Many birds, including martins, will gather in large numbers to spend the night. Many wading birds will congregate in estuaries. It is during this time that many migrants form the flocks that they will travel with. Martins, however, are thought to migrate in loose, small groups."

Here is a link, from 2004, with a map for searching out known roosting sites at that time:

http://www.purplemartin.org/roost/map.php

Googling "Audubon Martin Roost Events" will bring up a list of roost watching events and associated festivals in locations such as Tulsa, Houston, New Orleans, and more.

Finally, click for information on turning in a new roost report here.