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
>
>
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