i told jerry that when i had a bunch of juveniles( as a rehabber you
get tons of babies and juveniles for various reasons), they would be
housed in a screened cage - they would all bunch up together and cling
to the screening , only needing enough space( ie wall space) so each
one could grip onto the screening - maybe someone on this list has or
knows of a source of a photo of the inside of a chimney - i wish i had
taken pics of these ones i had for rehab - christie huffman
Begin forwarded message:
From: "Jerry Blondell" <jblondell@xxxxxxx>
Date: October 11, 2009 11:27:16 AM EDT
To: "Christie Huffman" <crhuff55@xxxxxxx>
Subject: Width of a Chimney Swift? . . . and length in a crowded chimney???
Hi Christie,
This past week I got some better videos of those chimney swifts going down the chimney at Ft. Belvoir. And now I'm obsessed with getting measurements. My current estimate for the inside surface of the chimney is about 110,000 square inches. That's assuming it's 50 feet high which I'll verify later today. So how many birds could fit in such a chimney. Well they have 14" wing spans according to Sibley or 7" long wings and then allow 3 inches (?) from wing shoulder to head, would give 10". Then I figured the body is about 1 to 2 inches wide? But haven't found the width on the internet or any of my bird books (width with wings folded).
I found a fascinating reference by J. J. Audubon that claims the chimney swift (back then, in 1808, it was called the American Swallow) takes up about 3" (??? implying great overlap from head to tail) by 1 and 1/2 inches. He goes on to do just what I'm doing, calculate the number of birds that one large hollow Sycamore tree held in KY (he estimated 9,000). He even goes inside the tree at night to observe the roost with a lantern after cutting and sealing a hole in the side of the tree.
So here's my two questions:
1. Is Audubon right - is 1.5 inches a good measure of the width of a chimney swift (with it's wings folded)?
2. I haven't found a single photo of chimney swifts inside a large roost on the internet, but maybe you've come across something. Do they overlap from head to tail? Or do they space out tip of tail to tip of beak?
I got more and I hope clearer videos last night and posted the last 4 from a visit earlier this week at the website below. Check out the 7th and 8th photos/videos here:
http://picasaweb.google.com/jblondell3/ChimneySwiftsAtFortBelvoirChimneySept2009
I'll do a proper nature notes including what I've already sent but also Audubon's experience and others from the early 1900s on these fascinating birds. I don't know if Sarah Frye is still around but if you have an email for her and could share this note, I'd appreciate your forwarding this note to her. Maybe she can help with the answers. I expect she may have written what we have in the hotline manual about chimney swifts, which I plan to quote from in my nature notes.
If, as I originally thought the chimney swift takes up 15 square inches (10 inches long by 1.5 inches wide) then the Ft. Belvoir chimney would hold exactly 7,333 swifts with no overlap. Given that my estimate for the number going in this one chimney is a minimum of 2,000 and perhaps as many as 5,000 - the implication is that most of the interior surface of this chimney is fully occupied! One thing Audubon helped me with, was the observation that none of the swifts perched on the back of each other.
I'm going back to the chimney today to verify its exact height. Last night I verified it's circumference, but it didn't occur to me how easily I could get the height with basic trig. until I woke up this morning. Simply cut a square piece of cardboard diagonally and walk away from a chimney or tree until the top of the cylinder is along a 45 degree diagonal. Then the distance between you and the chimney or tree and the height of the tree are the same (be sure to add the height of your eyes above the ground).
This is the kind of thing I do for fun!
Jerry
703-455-3647
