Chimney swifts by the thousands flock to Imperial plant
By CINDY HORSWELL
HOUSTON CHRONICLE
Sept. 5, 2009, 7:37AM

>>> Beginning of the exert from the article

The historic landmark symbolizing Sugar Land's roots — the Imperial Sugar refinery — has been going to the birds without anyone noticing until now. (Texas)

Authorities have discovered that just before dusk as many as 10,000 chimney swifts are converging there to spend the night clinging to the inside walls of an exhaust stack rising behind Imperial's glowing neon rooftop sign at U.S. 90 and Oyster Creek in Fort Bend County.

According to bird enthusiasts, this roost may be the largest known to exist on the Gulf Coast and one of the largest in the United States for these small gray birds, whose numbers are in decline.

>>> End of the exert from the article

I took this photograph in twilight time before the flock of thousands descended into the chimney on the left. Sunset was at 19:38 and at that time there were less than 1000 swifts circling above the refinery stacks. However by 19:40 the swifts began to appear like swarms of honey bees by the thousands as they circled a few yards above the 2 smoke stacks.

The swifts began to converge towards the chimney on the left descending in swarms resembling a tornado vortex as they moved down towards the smoke stacks. Thousands passed the opening in mass with some descending and the rest circling back high above to rejoin the top of the vortex. This lasted for minutes or two until finally they disappeared into the opening as if the stack had become a huge "black hole" in which they began to spiral into. This continued for at least a full minute or more until the last ones disappeared into the darkness of the stack and dusk. So by 19:50 or 10 minutes after they began to swarm, the swifts had settled in for the night somewhere deep into the huge white smokestack.