Date: 7/31/20 4:05 pm From: Gordon Andersson <gpandersson...> Subject: [mou-net] Chimney Switts in St Paul
I live in W. 7th neighborhood of St Paul kiddiecorner from a school with a tall chimney. Every summer the CHSW's start chittering and flying around in small and large groups beginning about sunset. On Monday eve I decided to count them as they dove down the chimney. As you know, the most accurate count would require a video recording played back in slow motion. The number dropping into the tower accelerates suddenly and then it is over except for a few independent spirits.
On Monday eve I counted 92 birds. On Tuesday 142 birds. Last eve Thursday 122 birds. The last count is probably the most accurate with the smallest + and - ranges. But I think the numbers actually fluctuate each evening also. There might be a rolling average increase before departure for the south.
For years Audubon MN conducted a volunteer CHSW count at two times during the summer, with a retired volunteer coordinator. For 40+ years, St Paul Audubon Socy had a "warbler weekend" every Mother's Day weekend at Villa Maria in Old Frontenac on Miss River. Every evening Friday and Saturday people would count the birds going down the chimney of the 4 story limestone block residence. It was a scheduled event.
About 15 years ago, on a weekend, I came back from birding somewhere and decided to sit in my bkyard and count the CHSW's. This was before the AM organized count. As I remember there were 246 or so birds and I sent the observation to DNR non-game staff.
My thought with these summer tower roosters has been that they were all non-breeders. Since they only appear in the evenings, they could not be feeding young in nests in the chimney. Someone who knows more and has actually studied CHSW's might offer some facts. I was told once that only one pair nests in each chimney. Alternatively, perhaps these birds are already swarming, preparatory to migration to Central America. a long ways to go and if young have already fledged they can head south.
This is from CLO allaboutbirds.org "Unmated swifts continue roosting together in the summer, sometimes in large groups. But the species does not nest colonially: you'll find only one breeding pair nesting in any one chimney. The pair may tolerate other nonbreeders roosting in their chimney."
This represents a huge number of non-breeders. CLO does not mention age of sexual maturity. The loss of chimneys has been gradual over time so these numbers are not due to a sudden surplus of adult birds from one year to the next.
PS I just read Jim Williams article in the Star Tribune from July 28 on Chimney Swifts. He notes the decline of all four of N America swift species, that NAS labels as species of "special concern".