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

so far.

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.