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Re: Purple Finches: Male or Female?
- To: carolinabirds@duke.edu (CAROLINA BIRDS)
- Subject: Re: Purple Finches: Male or Female?
- From: "BILL HILTON JR. (Hilton Pond Center for Piedmont Natural History)"<hilton@hiltonpond.org>
- Date: Tue, 8 Feb 2000 10:19:54 -0500
- Sender: carolinabirds-owner@acpub.duke.edu
CHRIS . . .
Thanks for the note. As stated, the assumption is a flying leap of
faith. Nobody knows the answer to your question, in part because we
don't have many banders between Conway SC and Pennsylvania.
In the first place, I think PUFI are facultative migrants, perhaps
coming down only when the sunflower seeds run out at feeders in
Massachusetts. This may or may not be age- or sex-related. There may
also be a foraging difference that leads to a trapping bias; maybe
males like feeders better.
You'd think we'd have the answers on all this, since PUFI are a
common winter feeder bird. The only possible solution is to build the
bander base in the Southeast and to have a lot more foreign
encounters and later-year retraps. Or we could start doing
laparotomies on every bird to determine sex. I did it on 1,500 Blue
Jays, but I don't much want to on PUFI. :-)
Cheers,
BILL
*********
>On Mon, 7 Feb 2000, BILL HILTON JR. (Hilton Pond Center for Piedmont
>Natural History) wrote:
>
> > CarolinaBirders . . .
> >
> > The thread on sexing Purple Finches (PUFI) at the feeder has been
>interesting.
> >
>[snip]
> > It's difficult to get an accurate sample of sex ratios in PUFI
> > without banding them; I'm fortunate to have that privilege, and have
> > found here at Hilton Pond that red (actually, I prefer "raspberry")
> > After-Second-Year male PUFI make up about 28% of the winter
> > population, while about 72% of them are brown, i.e., old females,
> > young females, or young males. If we make a flying leap of faith and
> > assume the M:F ratio among PUFI is roughly 1:1, we might conclude
> > that each of these three age/sex classes makes up about a third of
> > the brown birds.
>
>What I keep wondering is why we should assume that the sex ratio is
>anything close to 1:1 in the Carolinas in winter. Many birds show
>differential migration, with males wintering farther north than females,
>which means that at the south end of the wintering range, most birds are
>females. Is there reason to think that Purple Finches *don't* show
>differential migration?
>
>Chris Hill
>Coastal Carolina University
>Conway, SC
**********
BILL HILTON JR., "The Piedmont Naturalist"
Hilton Pond Center for Piedmont Natural History
1432 DeVinney Road
York, South Carolina 29745
USA
e-mail: <hilton@hiltonpond.org>
Voice: (803) 684-5852
eFax: (503) 218-0845
Operation RubyThroat Website: <http://www.rubythroat.org>
Hilton Pond Website: <http://www.hiltonpond.org>
"Never trust a person too lazy to get up for sunrise or too busy to
watch the sunset."
BHjr.
**********