From: Michael Bradbury
Date: Tue, 19 Oct 1999 13:47:20 -0500
Subject: Swainson's hawk migration
For those of you who did not know, the TAC is continuing the migration study
this year. Microwave Telemetry loaned us 3 transmitters, and we retrieved
one, which was refurbished. I'm not sure what information you have received
from last year's work, so I'll give you a summary of information accumulated
We have migration and/or location data on 10 birds from past years. Of
those ten, 7 wintered in Mexico/Northern Central America, 2 wintered in
Columbia, and 1 wintered in northern Argentina. Our observations of
Swainson's hawks in Mexico indicate that Swainson's hawks from other North
American nesting populations are likely wintering in Mexico as well (based
on observed ratios of color morphs).
Of interest, for hawks which we have two years data, albeit sparse 2nd year
data, individuals appear to return to the same wintering areas (which is no
surprise given their high fidelity to nest sites year after year). Also,
the male and female of a mated pair did not winter together; one wintered in
Central Mexico, the other wintered in Columbia.
This year's data:
As of Oct 18, 3 tagged birds are together in northern Sinaloa, Mexico, and
the last bird is SW of Bakersfield, CA, likely using a eucalyptus grove that
is a known roost site for SWHAs.
The TAC will be trying to develop a partnership with researchers in Mexico,
both at the Raptor Research Foundation's Meeting in La Paz this November,
and in the TAC's yearly visit to the wintering grounds in February.