Re: House Finches

["John CAVITT" <JCAVITT at weber dot edu>]

Hello all

The disease in House Finches that typically is responsible for deformed
bills etc. is avian pox.  Mycoplasmal conjunctivitis (the disease
responsible for eastern population declines) has not really affected
western populations, yet.  My students and I have been studying disease
in UT finches for the last several years and the incidence of avian pox
is very high.  Despite sampling 100's of birds for conjunctivitis we
haven't found it in northern UT.  Typically avian pox is not itself
fatal  (unlike m.c.) but it can make the birds prone to secondary
infections and malformations which can reduce their ability to feed or
escape predators.  I find it interesting that Tim reports seeing
orange/yellow morph of Cassin's.  Avian pox does indeed result in these
color morphs in HOFI (see article in UT birds - Spears and Cavitt 2003).
 No one is sure how it does this but it may be that the virus interferes
with the birds ability to synthesize carotenoids from the diet which
produce the colored plumage.  I would assume one could get the same
response in Cassin's but as far as I know it hasn't been reported in the
sci literature.  The impact of this virus on plumage coloration is a
real population problem because we know that female HOFI preferentially
mate with red males (the redder the better).  These males have also been
found to be better fathers (they deliver food to nestlings at a higher
rate than the yellow/orange males). 


My students and I have found that the incidence of avian pox is much
higher in more urbanized habitats where the birds frequent feeders.  


Spears, L. and J.F. Cavitt. 2003. The prevalence and effects of avian
pox on body condition and plumage coloration in northern Utah
populations of House Finches (Carpodacus mexicanus).  Utah Birds
17:25-33.



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
FAX: (801) 626-7445
homepage: http://faculty.weber.edu/jcavitt




"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

>>> "Tim Gorman" <wyogoob@allwest.net> 11/29/2004 11:05:26 AM >>>
Typically each winter on the Wyoming / Utah border in Evanston we have
moderate numbers of House and Cassin's finches.
For the last 2 years both species have nested here then disappeared in
September. 

The last year we had good numbers of Cassin's was 2001. I even had one
orange and an unusual orange/yellow morph frequenting my feeder. But in
2002 many had some sort of disease. Their beaks were deformed and had
sores on them. Some had infected eyes. Maybe this is part of the
downward trend??

Also the Gray-crowned Rosy-Finches are not showing up. Around the
Holidays there used to be hundreds and hundreds of them; enough to drive
the House Sparrows off the feeders. Now there are but a handful. We see
them on the Deseret Land and Livestock Ranch on the Christmas Bird
Count. The Ranch rotates cattle grazing areas, resting many acres of
habitat that supplies food for the GCRFs. The rest of our land here is
stricken with years of drought and subsequent overgrazing. Gray-crowned
Rosy-Finches (and many other species) can't rely on human supplied food
alone. I believe there's just so little to eat they move on. 

The lack of weeds and weed seeds also minimizes the rodent population
and their feathered predators. Hawks, falcon, and owl numbers are down.


On the upside we had Redpolls last winter!!!

Tim Gorman
Evanston WY

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