Saturday, July 25, 2015

Purple Martins Move to Capital Plaza

This year, the roost of the Purple Martins in Austin moved from the Highland Mall, east a few miles to the Capital Plaza Shopping Center near IH-35 and 51st Street. The birds gather here after nesting season to congregate in preparation for their fall migration back to Brazil. A weekly series of Purple Martin Parties are hosted by the Travis Audubon group with permission from the Capital Plaza Shopping Center management. This was one of those nights and a crowd had gathered with people in lawn chairs. We arrived just before 8:00PM with a few dozen martins circling in the air over the parking lot along with a number of grackles. The number of martins quickly swelled and, by dusk, they covered most of the sky as they swirled in great undulating waves. The continuous chattering of the birds and the smell of their droppings assaulted the rest of the senses.

It was very hard to estimate the number of birds that swarmed around us. In recent years, the Austin roost has reported several hundred thousand birds. Reports on eBird for this site this year have grown over the month from 100,000 to 500,000 birds. There were clearly more birds here this evening than we saw last year on July 12 at the Highland Mall. Partly, this may be due to the later date, partly due to larger population. Purple Martin land lords, Susanne and Greg Harm, told me that their colonies fledged many more young this year, likely due to the rains providing an abundant food supply.

Last year, the roosting birds appeared to be more evenly distributed between blue adult males and brown juveniles and females. This year, there appeared to be many more brown birds - about only one in ten birds I saw was blue. Susanne told me that this was because there were so many more juveniles successfully fledged this year. Below is one of the juvenile males starting to grow adult blue feathers on its belly and head.

Next is a slide show of some of the close up shots of the birds as they landed in the trees behind Chase Bank. The first panorama was taken with an iPhone. All other images were taken with a Canon 7Dii, EF 100-400 f/4.5-5.6 lens, and flashed using a Speedlite 600EX-RT with a Better Beamer.

We also took a short video to give a sense of the magnitude of the flock. Watching them swarm is much more dramatic than the bats at Congress St. Bridge.

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