As promised, here is a very conservative estimate (actually two estimates)
of the number of swifts emerging from the Monroe Elementary School chimney
on Saturday, September 3:

As posted earlier, I took video clips at 1-minute intervals and counted the
birds emerging for the first 5 seconds of each clip. There were nine clips,
covering a period of 8 minutes (480 seconds) from 8:07 when birds started
emerging until 8:15, after which few birds emerged but quite a few went back
in. (If planning to go watch birds emerge, note the post that they emerged
about 6:20 the prior day.)

3332 estimated if each 5-second count is used to represent 60 seconds
(thirty seconds for first and last counts)

3349 estimated if the total for the nine 5-second counts (314) is multiplied
by 480/45, i.e., the total time, in seconds, divided by the 45 seconds
involved in nine 5-second counts.

I counted only the birds visible from ground level as they came up over the
rim of the chimney and ignored the fact that some were leaving, unseen, over
at least the far side of the chimney. From my angle I could clearly see two
sides of the square chimney and at least some of the birds going over a
third side. (To correct for unseen areas , I would have to multiply the
estimate by 4/3 or more, suggesting at least 4000 birds.)

A better count and estimate could be made from a camera point closer to the
chimney height and, since not all birds seem to come out with the main group
in the morning, as birds are turning in for the night.

If you are interested, here are my data:

Time 5-second count

8:07 33
8:08 29
8:09 25
8:10 41
8:11 43
8:12 48
8:13 35
8:14 37
8:15 23

Al Wagar
Shoreline

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