http://www.exoticfinches.com

Warning: All rights reserved. This article appeared in the issue of the National Finch and Softbill Society Bulletin. Volume 20. No. 6. November/December. 2003. p. 10. Anyone wishing to reproduce this article for another bulletin, newsletter, article, journal, CD, or any other public forum needs express written consent of the NFSS and of the author michael@exoticfinches.com

I have accepted the role as science editor (Martie begged me) and have agreed to review any controversy that deals with the genetic and other biological aspects of submitted finch articles. In the meantime, I'll try to add some interesting notes to each issue of the NFSS Journal (being prodded bi-monthly by Martie). Below is my first submission

Sex Ratio Reseach Reviews

If you are like me, you are perpetually frustrated that your birds give you more males when you want hens and more hens when you want males. In my case, I've had a ratio of 2:1 male to female in my society finches for years and no "old wives tale" remedies seem to change this. I breed year round, have tried black (aka U.V.) lights here and there, and have naked pictures of both male and female birds hanging in each nest box :-) It appears that bird sex-determination is more interesting and complex than you would ever imagine and still an area of active research. For example, consider these findings published in well respected journals.

In Animal Behavior, (Volume 56 pages 155-164.), R. Kilner reports that how much food zebra fledglings receive may have a profound impact on reproductive success. When food was restrictedrather than unlimited, clutch ratios were significantly more male biased. Within clutches, daughters hatched sooner than sones and first-hatched chicks fledged at higher weights than last hatched chicks. Chick mortality was female biased when food availability was low but male biased when food availability was unrestricted.

In the prestigeous journal Nature, Ben Shelden and colleagues report (Volume 402, pages 874-877) that ultraviolet color variation influences blue tit sex ratios. Blue tits are sexually dimorphic primarily in the UV (A) color range having blue structural color in the males. Interestingly, female can skew the sex-ratio of their clutches in response to UV (A) plumage ornamentation of males. When they experimentally masked the male ultraviolet output they effectively altered sex ratios in subsequesnt clutches. UV (A) reflectancealso predicted male survival to the following season suggesting it may serve as a viability indicator. The importance of this findeing (and no news to me from my years of skewed sex ratios) is that chromosomal sex determination may not constrain the sex ratio in some birds. As a side note, I am wondering if this explains why UV light does not seem to have an effect on my sex ratios. Society finches do not have strucutural blue color whereas gouldians, e.g. do. So when you read Robert Black's testimony to UV light treatments take in mind he generalizes and gives no explanation as to why it works. Any one out there that can tell me how to alter my sex ratios in societies gets two boxes of chocolates if it works!

---