In Waukesha County, at Okauchee Lake, on Wisconsin Avenue, there is the Old
Norris School. This has been a continuing chimney swift Roost for decades
according to people who used to attend the school. Nightly roosting
behavior has been occurring this fall and last night had a increase in the
amount of birds that I have seen over the past 3 weeks. Whether this was
due to a beautiful clear night or additional Swift migration coming into
the area...it may be both with additional causes like flying insect
availability, and light intensity. Last Saturday, the Swifts started
collecting and entering the chimney before Sunset, but with some overcast
at that time, the light intensity may have encouraged them to enter
earlier. Yesterday on Tuesday, with a virtually clear sky, the Swifts
hardly collected over the site and few entered the chimney until at least
15 minutes after sunset at 7:11 p.m. At that time Swifts started pouring in
from all directions forming a cloud that was larger than normal, they were
circling clockwise around the chimney, and then started entering the
chimney in large groups and flow. There were several moments of pause where
I would guess that the birds that had gone in were establishing position
and the others were waiting for that large number to settle down. My
estimate was that there were over 3500 birds entering. The surprise was
that other than a few hundred Swifts generally flying around the area
before sunset, the majority of the Swift arrived later and then got into
the swirling pattern, seemingly entering later than normal in large
numbers. It will be interesting to see in the coming days what subsequent
observations will observe regarding numbers of the Swifts and when numbers
will be decreasing as they migrate south, and how this might be affected by
the light intensity and the insect availability, which is also linked to
the temperature.
In any regard if you are not already at a swift roost that has a
significant numbers, it would still be fun for you too see these birds at
Okauchee, before the show ends. New visitors either single, or couples, or
families... Young and old, local and from some distances have been visiting
these evenings thanks to your sharing. Please keep it up. Thank you.
Old Norris School
N50 W35057 Wisconsin Avenue
Okauchee, WI ... Waukesha County
Spence
Spencer Stehno, President
Ben Goss Bird Club, Waukesha
414-940-2020
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