Birders, I'll also start by saying that genetics isn't my field of expertise. I'd like to add something I recall (hopefully correctly) from my high school genetics class (too many years ago). A Ross's Goose that appears perfectly "normal" in all respects, could have Snow Goose genes; first generation (f1) hybrids will often look like one of the parents, showing no intermediate characters at all. -- Allen T. Chartier Inkster, Michigan Email: [log in to unmask] Website: www.amazilia.net Blog: http://mihummingbirdguy.blogspot.com/ On Wed, Dec 14, 2011 at 5:49 AM, Paul Gardner <[log in to unmask]> wrote: > Welcome to Ohio-birds. > > Genetics isn't my field of exper > Hi Chuck, > > Welcome to Ohio-birds. > > Genetics isn't my field of expertise, but I believe your notions about > hybridization are correct. Apparently many of hybrids are fertile, and like > you suggested, they would be more likely to mate with a "pure-blooded" bird > than another hybrid, since there are so many more "pure-blooded" birds. > Since each parent provides one-half of the genes of its offspring, if the > descendants of a hybrid always mate with the same species, then the genetic > contribution of the aberrant ancestor is reduced by 50% each generation. > Presumably at some point, the expression of these genes in the population > would no longer scream out "hybridization", but rather would be seen as > part of the normal variation of species. > > On the Frontiers in Identification web site > <http://www.birdingonthe.net/mailinglists/FRID.html#1323233292> > there is some discussion of a recent paper in The Auk that deals with this > phenomenon. Apparently the authors give it the seasonally apt name of "the > ghost of introgression past". > > As I understand it, if we observe, say, a small Snow Goose, we can't > really know if its small because > (1). it has all Snow Goose genes which happened to sort out it a way that > creates small size, > (2). it has all Snow Goose genes that should have been expressed as normal > size, but bad nutrition or other environmental factors limited the bird's > growth, or > (3). one or more ancestors was a Ross's Goose and those genes are being > expressed as small size. > > All we can do as birders is rely on a combination of field marks, then > make a personal decision as to whether the bird "looks good enough" to be > added to our list. > > Happy birding, > Paul > > Paul Gardner > Columbus, OH > > > --- On Mon, 12/12/11, Chuck Slusarczyk Jr. <[log in to unmask]> wrote: > > > From: Chuck Slusarczyk Jr. <[log in to unmask]> > > Subject: Re: [Ohio-birds] Ashtabula Goose ID Debate > > To: [log in to unmask] > > Date: Monday, December 12, 2011, 11:15 PM > > Hi All, I'm a new poster, but have > > been lurking for a while and find this > > site very informative, thank you all. > > > > I too found this conversation very interesting, and agree > > that sometimes you > > just may never know for certain. > > > > In reference to this discussion, I have a few questions > > that have been > > running through my mind, and please forgive me if it's > > already been > > discussed because I haven't seen it. > > > > Are these hybrids mules or can they reproduce? If so, > > could some of this > > variation be attributed to hybrids mating with other > > hybrids or even pure > > members of the two species? > > > > A hybrid x hybrid match seems unlikely to me, but not > > impossible. A hybrid > > x pure pairing seems probable as long as these birds are > > viably > > reproductive. I may be wrong in my thinking, but > > would the progeny of a > > Snoss x Snow pairing be 75% Snow, and conversely, a Snoss x > > Ross pairing be > > 75% Ross's? > > > > Just throwing that out there. > > > > -Chuck > > > ______________________________________________________________________ > > Ohio-birds mailing list, a service of the Ohio Ornithological Society. > Our thanks to Miami University for hosting this mailing list. > Additional discussions can be found in our forums, at > www.ohiobirds.org/forum/. > > You can join or leave the list, or change your options, at: > http://listserv.muohio.edu/scripts/wa.exe?LIST=OHIO-BIRDS > Send questions or comments about the list to: [log in to unmask] > ______________________________________________________________________ Ohio-birds mailing list, a service of the Ohio Ornithological Society. Our thanks to Miami University for hosting this mailing list. Additional discussions can be found in our forums, at www.ohiobirds.org/forum/. You can join or leave the list, or change your options, at: http://listserv.muohio.edu/scripts/wa.exe?LIST=OHIO-BIRDS Send questions or comments about the list to: [log in to unmask]