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Finch Follow-up



Hello All,
 
My posting regarding mycoplasmal conjunctivitis in finch populations has already generated some very good points and some questions.  Both of which I would like to address in this group email format for efficiency's sake.
 
First there was an excellent point brought up regarding avian pox.  Avian pox is relatively common among wild birds and the  confusion of its symptoms with mycoplasmal conjunctivitis is very possible.  Both diseases can cause swelling and malformation of the area around the eyes.  The differences that do exist between the two ailments exist within the cause and manifestation of the diseases.  Mycoplasmal conjunctivitis is caused by the bacterium Mycoplasma gallisepticum (MG) and is a respitory disease.  The outward symptoms of MG infection are confined to the head; namely red, swollen, runny, crusty eyes and nares.  Conversely, avian pox is a virus and results in warty growths on the unfeathered portions of the feet, legs, wings, and face.  As such, when you are watching a sick bird, pay special attentions to the feet and legs to help identify the illness (if lumps are present it is likely avian pox).  In either case, report your findings.
 
Secondly, there was some question regarding the host specificity of the MG pathogen.  To date, it has been found in the following wild bird species besides house finches:  American Goldfinch, Purple Finch, Evening Grosbeak, and Pine Grosbeak.  All members of the family Fringillidae.  House finches are far and away the most susceptible of the finches.  Hypotheses surrounding the house finch's high level of susceptibility stem from the origination of the eastern house finch population.  Originally only found on the west coast, house finches were released in around New York City in the 1940's and spread rapidly across the U.S.  Because the Eastern population was founded by such a small number of individuals, which necessitated inbreeding, today's population exhibits low genetic diversity.  Combined with the characteristic to form large, mobile flocks, genetic depression of the house finches has facilitated the spread of the disease through the population.
 
Thirdly, there is some question of the consequences of this disease with regards to the sustainability of finch populations.  Using the east coast as a template (they have had the disease in their wild finch populations for 8 years now) to forecast what we can expect, leads us to be conservative in the disease's effects.  On the eastern seaboard after the initial epidemic, mycoplasmal conjunctivitis infection rates equilibrated at between 5% and 10%.  Although there appears to be no immediate threat of a dramtic population wide finch decline, gathering information regarding the spread of the disease is still very important from the perspective of human impacts on passerine species.
 
Finally, a note should be mentioned about feeder hygiene.  Although, feeders are reported to not have a net negative effect the following guidelines from http://birds.cornell.edu/hofi/hofifaqs.html should be followed to maintain healthy environment for the birds: 
 
1) Space your feeders widely to discourage crowding.
 
2) Clean your feeders on a regular basis with a 10% bleach solution (1 part bleach and 9 parts water) and be sure to remove any build-ups of dirt around the food openings. Allow your feeders to dry completely before rehanging them.
 
3) Rake the area underneath your feeder to remove droppings and old, moldy seed.
 
4) If you see one or two diseased birds, take your feeder down immediately and clean it with a 10% bleach solution.
 
Happy birding!
 
 
Adam Kozlowski
Native Species Biologist
Utah Division of Wildlife Resources, Northern Region
515 East 5300 South, Ogden UT  84055
Office:  (801) 476-2740
Cell:  (801) 510-2034
email: akozlowski@utah.gov