[Bristol-Birds] Re: 10,000 Cliff Swallow Nests
- From: michael sledjeski <mtnsylva@xxxxxxxxxxxxx>
- To: bristol-birds@xxxxxxxxxxxxx, Wallace Coffey <jwcoffey@xxxxxxxxxx>
- Date: Sat, 18 Jun 2011 16:26:25 -0400
Wallace,
I've counted cliff swallow nests on Rankin Bridge for several years and found
unequal occupied-nest numbers, with a difference of about 25%, on the north &
south sides. On the new Huff (Bridgeport) Bridge in Cocke county, all 220
nests are on the south side. I'm not sure that doubling the number seen on one
side would give a fair approximation on a particular bridge; with many bridges,
I suppose the error could average out, if the side counted were chosen randomly.
In my experience, many nests may be unoccupied leftovers from other years, or
partly damaged and not in use. Several years ago, of nearly 1100 nests or nest
remnants on Rankin Bridge, only about 700 were active. Seems to me that a
nest occupancy ratio should be factored into the final results.
Some nests can be seen only from beneath a bridge; as you've noted, they're not
always along the outer beams. From a canoe, I've counted as many as two dozen
inner nests on Rankin Bridge.
How many cliff swallows are nesting on cliffs these days - have any been
reported lately? From what I've seen, it might be more appropriate to call
them Bridge Swallows.
Michael Sledjeski
Del Rio, Cocke county, TN
On Jun 16, 2011, at 8:42 PM, Wallace Coffey wrote:
> A structured, projected, number of Cliff Swallow's
> nests in the Holston River drainage of Sullivan
> and Washington counties in Northeast Tennessee
> today arrived at more than 10,000 nests on bridges
> over lakes and rivers.
>
> That is a personally "awesome" number when I
> reflect on the fact that 40 years ago I found three
> nests under a bridge over Boone Lake at
> DeVault Bridge Rd. on the South Fork Holston River
> arm of the lake on 18 May 1971. That was the only
> known nesting in Northeast Tennessee at that time. It
> had been almost 25 years since nests were found in
> a barn near Elizabethton in 1947.
>
> I was helping TVA biologists electro-shock fish in the
> reservoir aboard a TVA research boat when I saw the
> three nests. We were collecting fish to gather mercury
> samples from their flesh for a water quality study. I went
> back four days later, asked a marina operator to loan
> me a boat, and went to the site and made color photos
> of the nests and adult birds (Knight 2nd. 2008, p.70).
>
> An actually survey of the number of Cliff Swallow nests
> on Boone Lake today found approximately
> 3,100 nests over standing reservoir water (below
> creek and river fall lines). The breakdown for
> bridges I actually visited and made estimates of
> in the survey is shown below in green.
>
> A projected guess at 24 additional sites along the
> South Fork Holston River in Sullivan County to
> include South Holston Lake (TN), Patrick Henry
> Lake and the river running thru Kingsport as
> well as a couple sites on the North Fork Holston
> River in Sullivan County at Kingsport. All are
> of the projected 7,000 nests are shown in blue.
>
> These guesses, in many cases, are based on
> seeing and counting nests in past years at
> several of the sites and having some idea of
> what could be there.
>
> The actually field survey of Boone Lake took
> almost 7 hours and many miles driving. This
> would have been much more difficult and time
> consuming without a GPS to pick up shortcuts
> and exact bridge locations.
>
> The method included the following: Driving to
> a bridge location, I would count and estimate
> the actual number of nests at the site. For
> instance, at Pickens Bridge, almost all of the
> nests were on the bridge abutments which
> support the bridge. This is because of the
> concrete design. Traveling around nearby
> roads and setting up my scope to get a
> reasonable estimate for the number of nests
> on one side of abutments, I would then double
> that for a total of both sides (number for that
> abutment) then multiply by the number of
> abutments. Where the bridge had a major
> span and the nests were on the outside and
> under the span, I would estimate one side by
> as much visual count as possible and then
> double that for the other side. In one case
> US11E (Charlie Worley Bridge) at Bluff City,
> the nests appeared to be on the upstream
> side only so that is all that was included.
>
> Rather than get into a completely unrealistic
> posture, I did not try to list numbers below
> a 100 level. Almost all bridges had a large
> enough number to include the above estimate
> formula.
>
> Nevertheless, I obviously made some misjudgments
> but I did try very hard to be realistic and accurate.
>
> Boone Lake
> Pickens Bridge 400
> DeVault Bridge US 11E 100
> Knob Creek Rd. 200
> Austin Springs 300
> Herb Hodge Rd. 100
> Enterprise Rd (Rainbow B.) 700
> DeVault Bridge Rd. 600
> Bluff City 300
> NS Railway (Bluff City) 0
> Bluff City swinging bridge 0
> US 11E Bluff City 2 spans 400
>
> BOONE LAKE SUB TOTAL 3100
>
> South Holston Lake (Projected)
> Dam emergency tower 200
> US 421 500
>
> SF Holston River to Bluff City
> Holston View Dam Rd. 600
> Rt. 44 300
> Weaver Pike 200
> Old Weaver Pike 300
>
> Rt 75 (new) 0
> Beulah Church Rd. 400
> I-81 2 spans 400
> Fall Creek Rd. 400
> Cooks Valley Rd. 200
> Fort Henry Dr. 400
> CSX Railway 0
> John B Dennis 300
> Eastman Access 0
> Jared Dr 200
> Ivory St 100
> S. Wilcox 400
> Riverport Rd. 100
> Netherlands Rd. (new) 200
> I-26 Netherlands Rd. 800
> i-26 Riverport Rd. 500
> Manor Dr 100
> Ridgefield Rd. 400
>
> Subtotal 7000
>
> PROJECTED TOTAL 10,100
>
> It would be a wonderful contribution if some birders
> might actually go to any of the above sites and get
> as accurate numbers of nests. The large the bridge,
> the more the nests, the more difficult it is to do
> anything more than get a good estimate.
>
> I will not be offended by anyone finding no nests
> where I projected nests in blue. And I will not be
> offended at all if you get larger, smaller or more
> precise number counts than I did today.
>
> It would actually take me a week to try and get
> an actual eyeball on every possible site. Even
> with a boat, it would take more than a day to
> visit all the sites and make an actual count of
> all nests -- one by one.
>
> Half of something is better than all of nothing.
>
> Big blackbird roosts estimates, massive hawk
> flights and very large waterfowl and gull rafts
> all present similar problems but we never hesitate
> to give it our best determinations.
>
> This is a slow time of year for Bristol-Birds so
> feel free to put your numbers up with your name
> on them. Sending them to me in private is
> asking me to hide your identify. I can't do that
> and get anything accomplished.
>
> Please help.
>
> Wallace Coffey
> Bristol, TN
>
>
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