What Makes for a Big Roost?

[AvianStewardess]

Hello, Everybody. Season's coming along fine here on the Eastern Shore of Maryland; fledging started a few days back now. The one-who-tolerates-the-insanity asked me a question...of course I don't know the answer. So, here I am coming to the experts:

Are there are "features" or "attractions" or "somethings" similar that account for the really large roosts around the country? And, I know the site has a way of finding existing roosts in each state, but wondering if there is a "Top Ten: for around the country...

Thanks for entertaining the curiosity of it all! Greatly appreciated.

[lauriefoss]

I can speak to the roost characteristics in Austin, TX. It's size has been measured by a senior biologist at 600,000 birds. They roost at Highland Mall, Austin's first urban mall which was built in 1971. As far as we can determine, they have roosted there ever since.
The site is characterized by a large, open parking lot with lighting. They roost in Live Oak trees that are planted side-by-side along a driveway. There are about 12 trees that they use.
This roost has not always been this big. As recently as a decade ago, interested hobbyists estimated the size as 120,000 birds. I don't know what could account for the increase in size.

[jr 2]

the roost close by here in huntington west va, has been estimated at about 30 or 40 thousand;;it is in small trees downtown in business[not residenticial] parking lots well lighted at night and within walking distance of ohio river;was their last year and plan on checking it out this evening;;jr2