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Re: Purple Finches: Male or Female?



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

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>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.

**********