[Birdtalk] dead birds

[John CAVITT]

We had a crew out in an airboat this Tues in Farmington Bay near the
mouth of Kay's Creek doing shorebird work and they counted dozens of
dead or dying birds.  

Unfortunately most everything we know about avian botulism has come
from studies at the Great Salt Lake.  The nature of the GSL (shallow)
makes it a prime site for outbreaks.  As Mark indicated the disease is
caused by a bacteria (Clostridium botulinum) which secretes a toxin.

One of the most widely cited hypotheses for botulism outbreaks is the
microenvironment concept or the bird-maggot cycle (proposed by Bell et
al. 1955).  This suggests that Botulism outbreaks can occur whenever
there is a sudden change in water levels (either an increase or
decrease).  This is due to the sudden buildup of nutrients at the soil
surface (either dead terrestrial inverts when an area floods or aquatic
inverts when a site dries out).  This buildup allows the bacteria to
flourish on the dead organisms rather than in the soil.  Consequently
the toxins secreted are easily ingested by birds.  Unfortunately you get
a positive feed back loop with these outbreaks because as birds die this
creates further media for the bacteria.   As Mark indicated temperature
is also a critical factor in that warm weather provides optimal growth
of bacteria.  Peak outbreaks at GSL run from July through the end of
October. 

Incidentally avian cholera is another disease that can result in large
die offs but it is not as common as botulism at the GSL and seems to be
more prevalent in winter (Nov - Jan.).

Cheers

JFC

  





John F. Cavitt PhD, Director
Office of Undergraduate Research
Associate Professor

Mailing Address
Dept. of Zoology
Weber State University
2505 University Circle
Ogden, UT 84408-2505

(801) 626-6172
(801) 626-8541
Avian Ecology Lab 
(801) 626-8634
cell:(801) 791-4438
FAX: (801) 626-7445
homepage: http://faculty.weber.edu/jcavitt
http://departments.weber.edu/avianecologylab





"A thing is right when it tends to preserve the integrity, stability,
and
beauty of the biotic community. It is wrong when it tends otherwise."


Aldo Leopold


>>> Mark Stackhouse <westwings at sisna.com> 9/15/2006 1:48 pm >>>
Hello,

I can address the botulism issue, as it was  something with which we 
came into direct contact while I was working at Tracy Aviary. The 
bacteria that produce the botulism toxin (it's the poison that harms 
the birds, not a bacterial infection) exist naturally in he mud at the

bottom of the lake, and in any body of water where there's mud that has

organic matter and is anaerobic (lacking oxygen). Normally, there isn't

enough activity of the bacteria to cause a problem, but when low water

levels and warm weather allow the mud to be warmed, the activity of the

bacteria explodes. The toxins build up in the mud, and waterfowl 
feeding in the mud become poisoned. The toxin causes paralysis, 
generally first in the legs and lower parts of the body and then 
progressing upward and finally causing death, either directly by 
shutting down respiration, or through starvation because the bird can't

feed.

There have been botulism die-offs at the Great Salt Lake periodically 
throughout recorded history. They usually have occurred in the late 
summer of hot, dry years when water levels are low. There were terrible

episodes in the early part of the last century, especially in the Bear

River Bay area, involving tens of thousands of ducks. These episodes 
were apparently aggravated by water withdrawals from the Bear River, 
causing low water levels in the bay. The public outcry was great, and 
was (I've been told) one of the main reasons why Bear River Refuge was

created - to preserve sufficient water in the bay to prevent further 
mass die-offs. It's something to consider as we contemplate damming and

taking more water from the Bear . . .

Anyway, cool, wet weather and rising water levels should alleviate the

situation soon, as it always eventually does.

Good birding!

Mark Stackhouse
mark at westwings.com 
801-487-9453 (Salt Lake City, Utah, USA)
011-52-323-285-1243 (San Blas, Nayarit, Mexico)

On Sep 15, 2006, at 11:42 AM, MUHLESTEINCLAN at aol.com wrote:

>
> Glenda,
>  I was out there last week, and was also amazed with the numbers I
saw 
> of dead waterfowl along the Causeway. I called Bill Fennimore, and he

> told me that they believe it is Botulism that has effected this area.

> He also said that because of the water levels being down right now, 
> that more contamination can be prevalent. He was going to pass on the

> information.
> I would also like more information concerning this dismal dilemma. 
> Anyone knowing more please respond to us.
> Thanks,
> MarJean M_______________________________________________
> Birdtalk mailing list
> Birdtalk at utahbirds.org 
> http://utahbirds.org/mailman/listinfo/birdtalk