I'm no geneticist, but it is common knowledge among breeders that there is some oddity in the chromosome number of them that prevent hybrid mandarins.
Aubrey,
I've been keeping wild waterfowl as long as you have, so I know the "common" knowledge (like, you cannot feed ducklings medicated starter because they eat more and will OD). Actually, in this case, the "common" knowledge goes back to:
Yamashina, Y. 1952. Classification of the Anatidae based upon the cyto-genetics. Japanese Coordinating Committee for Reseach in Genetics 111:1-34.
Yoshimaro goes into a long discussion on mandarins, thet he classifies as Dendronessa galiculata (not Aix). He actually has images of some incredible karyotypes (actually he lists then as n=42, vs n=40 in most other Anatinae, so I don't doubt his data, BUT on page 29 he states "However, it must be noted that the diploid number of Dendronessa accords with the basic number of chromosomes of other ducks." I believe this is a result of how "strange" avian chromosomes are. He regularly refers to micro and macrochromosomes, and some the the genetists I know talk about how unreliable karyptopes are bird birds. Several other species with different numbers of chromosomes such as his group Aastinae (including Anas, Cygnus, Tadorna, etc) and subfamily Anserinae (Anser and Branta) with an n of 45. There are numerous examples of duck goose hybrids (AnasxAnser; i.e. Poulsen, H. 1950. Morphological and ethological notes on a hybrid between a domestic duck and a domestic goose. Behaviour 3:99-104).
Paul Johnsgard, who spent alot of his career publishing on waterfowl hybrids published:
Johnsgard, P.A. 1968. Some punative mandarin duck hybrids. Bull. British Ornithol. Club 88:140-148.
He has p[ics of birds reported to be mandarinxlaysan hybrids, and mandarinxwood duck hybrids. The woodxmandarin hybrids that show greatly reduced sails, and generally poos plumage, like is often seen in hybrids. My take would be that MOST wouldn't recognize them as hybrids, just poor mandarins. The mandarinxlaysan hybrid would certainly suggest they could hybridize with calls.
Clint
