FreeLists / tn-bird / [TN-Bird] Re: Gull behavior on Clinch River

["Allan Trently" <ajtcorax@xxxxxxxxxxx>]

Good point.  Here's what Etnier (1993) says: They are less tolerant of cold 
water than is the gizzard shad, and populations in our cooler storage 
reservoirs can be extirpated or drastically depleted during severe winters." 
  "Sublethal effects, such as feeding cessation, can begin at 10 C (50F) and 
inactivity at 6-7 C (47 F); death occurs at 4-5 C (39 F) (Griffith 1978).  
In other studies cold-induced mortality occured at temperatures as high as 
12 C (55 F)."

Etnier also says that spawning occurs along shorelines and is typically a 
group activity.  Spawning is initiated in the spring when water temperatures 
reach 21 C (70 F) and may extend well into the summer.  I was told by an 
aquatic biologist that the shad are currently spawning.  I don't think the 
gulls care either way as long as they have plenty to eat.

Thanks for your comment.

Allan Trently, Terrestrial Zoologist
Tennessee Valley Authority
Norris, TN
ajtcorax@xxxxxxxxxxx





>From: "Raincrow" <raincrow@xxxxxxxxxxx>
>To: ajtcorax@xxxxxxxxxxx
>Subject: Re: [TN-Bird] Gull behavior on Clinch River
>Date: Wed, 4 Feb 2004 17:31:46 -0800
>
>Hi Allan
>I wonder if the large # of dead threadfins is also a matter of water 
>temperature? According to observations made by my ex in his aquatic biology 
>research days (back when we had winters and even a few inches of snow from 
>time to time), they started dying off in droves in early December; I forget 
>the magic temperature.
>
>Liz Singley
>Kingston TN
>
>----- Original Message -----
>From: Allan Trently
>Sent: 2/4/2004 11:47:48 AM
>To: tn-bird@xxxxxxxxxxxxx
>Subject: [TN-Bird] Gull behavior on Clinch River
>
>I watched ring-billed gulls below Norris Dam on the Clinch River on 
>February
>3rd.  The gulls were constantly flying up and down the river for short
>distances and intermittently diving into the water.  I noticed one bird had
>a fish in its bill after surfacing from a dive.  The fish was a threadfin
>shad.  There were many dead threadfins on the shoreline.  The shad are
>currently moving up-river to spawn.  This is a very stressful activity for
>the shad.  Many die on their migration up-river thus the dead shad on the
>shore.  The ring-bills take advantage of the 1000's of shad in the river.
>
>
>
>Allan Trently, Terrestrial Zoologist
>Tennessee Valley Authority
>ajtcorax@xxxxxxxxxxx
>
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       Neither the society(TOS) nor its moderator(s)
        endorse the views or opinions expressed
        by the members of this discussion group.
 
         Moderator: Wallace Coffey, Bristol, TN
                 wallace@xxxxxxxxxxxxxxxxxxx

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