Part II: The Gathering

This is the second article in a three-part series about my observations of Chimney Swifts. The site is the 1919 Building at 144 West Bridge Street in old Dublin.

Chimney swifts gather in large communal vertical roosts prior to their migration to the Amazon basin. A guaranteed time to see this natural phenomenon in central Ohio is between August 20 and Labor Day weekend. In 2003, the last bird departed on October 13.

A few years ago Darlene Sillick (AKA “The Bluebird Lady”) told me I should go watch the chimney swifts near Sells Middle School on Route 161. To witness the entire spectacle I arrived a full hour before dark. I got out my blanket and sat on the curb near the tennis courts and looked toward the chimney. Nothing. No birds. No bird sounds. Patience. Eventually about five birds came and circled the chimney, but quickly flew off again. Again, nothing. I sat alone enjoying the warm summer evening. Five minutes later about 20 birds flew in and circled the chimney, but after a few minutes they also departed. Five minutes later about 50 birds flew in and circled above the chimney. Now I began to pay attention. These had to be the chimney swifts and now my ears picked up their twittering, clicking sounds. But soon, as before, these birds flew off in all directions. I began to wonder. This chimney is like a magnet attracting the swifts. It is their “home base.” All day chimney swifts feed on the wing. Swifts are frequently found over water (the Scioto River is near this site) where they eat thousands of midges and mosquitoes.

As daylight decreases a few birds head home to the chimney. Finding no else home yet, they head back out in all directions, constantly twittering and calling to other swifts. It seems as if they are telling the others, “It’s getting dark. Time for bed!”

Every once in awhile an individual bird will drop into the chimney, but after 30-40 minutes there are hundreds (sometimes thousands!) of swifts circling overhead. The traffic pattern is generally counterclockwise, but occasionally the entire flock will abruptly change direction. Loud sounds, such as a dumpster lid crashing down, will temporarily scare off the flock, but that magnetic chimney soon draws them back.

At this point it is about 20-25 minutes until it is completely dark. The huge flock of circling swifts looks like a black oval smoke ring above the 1919 Building. The birds are continually communicating with each other. The entire scene is a sharp contrast to the quiet that one encounters an hour before dark.

Down They Go

As the swifts pass over the chimney, they dip down to “check it out,” but then continue around the circle again. Finally, a few swifts stop flapping their wings and literally drop into the chimney. About 20 disappear. With each pass, more and more swifts drop and soon it looks like “smoke going INTO the chimney.” On average it takes only ten minutes for 2000 birds to disappear into the vertical cavity. And it is over just as quickly as it began! Suddenly there is not a bird to be seen and it is eerily quiet. One can only imagine the cacophony inside the chimney as birds jostle for position for the night. They line up side-by-side in rows. Other types of swifts will even overlap like shingles on a roof.

Counting the Swifts

Darlene Sillick and I had always estimated the maximum number of birds at 1500. Although I had been watching the birds for two years, I only began to count them on September 10, 2003. How to count individual birds in that swirling mass? I figured I could estimate ten birds, so I fixed my eyes on the top of the chimney. Every time I thought ten birds had dropped in I made a tally mark on a paper. I never looked down at the paper, but kept my eyes fixed on the chimney. After all birds were in the chimney, I counted up my tally marks. I was amazed to realize that 3700 birds had entered the chimney! The following night Dick Tuttle (counts swifts in Delaware County) and Darlene joined me. 3800 birds. Sept. 12 saw 4300 birds. Sept. 14 was 4300 birds again. The peak number, 4500 birds, occurred on Sept. 15. With so many birds, it took longer for them to enter the chimney (7:45-8:10 pm). The very next night there were only 1800 birds so, obviously, more than half of the flock had moved on. Of interest is that the 1800 birds entered the chimney from 8-8:10. With a smaller flock, they adjusted their time to still finish at 8:10. The next night, Sept. 17, the flock had increased to 2700 birds entering from 7:45-8:15. Sept. 18 had 3300. The last two weeks of September had numbers between 2000-2800 each night. On Oct. 1 the flock peaked again at 3300 with most entering the chimney between 7:15-7:35. On October 6 numbers finally dropped below 2000 with 1800 swifts entering between 7:25-7:40. On Oct. 8 (70 degrees/clear) only 1100 birds went in between 7:28-7:32. On Oct. 10 only 650 birds entered between 7:24-7:29. On Oct. 12 I saw only 14 birds enter between 7:14-7:20, and on Mon., Oct. 13 (65 degrees/clear), no birds were heard or seen.

Dick Tuttle had been counting swifts in Delaware and he also witnessed a rapid decrease in numbers on Oct. 12 followed by no birds on October 13. The swifts at both locations certainly knew something that we humans didn’t know.

Everyone thinks the swifts hung around longer last fall due to the healthy mosquito population. On October 13 when there were no birds at all, I felt both sadness and a sense of relief. I felt sad because I feel “connected” to these little guys. But I also felt relieved to have more time to pursue other interests.

Part III will include my observations of the swifts leaving in the morning, the questions that have been raised in my mind, reporting data to SwiftWatch, other roost locations, websites and related readings, and plans for future observations.

Jenny Bowman, author of this series, has been the music teacher at Scottish Corners Elementary in the Dublin City Schools for the past 21 years. She is an avid amateur birder who has traveled to 58 countries.  She has been observing and gathering data on the swifts at this old Dublin high school for the past two years.