A THERMAL UPDRAFT VELOCITY of 300+ft./min. is a prime factor to carry waves of Broad-winged Hawks "when they decide that they must start their migration to S.America", this being in mid to late September along the north shore of Lake Ontario AND over land to the immediate north.
Now then, on Sep.12, the following conditions brought 1448 BWs over Cranberry Marsh RW and 1153 BWs over its satellite station, 10km. to the north, in Heber Down C.A.--the Iroquois Shoreline RW---TUV=300+. medium northerly winds and a rising barometric pressure. In addition CMRW reported 508 other raptor species, while ISRW had only 60 (incl. 3 Bald Eagles). On Sep. 13, the conditions were---TUV=300; very light E winds, and a steady BP. WHAT DID THIS MEAN?---CMRW had 5 BWs and 154 other species; ISRW reported 1461 BWs and 111 other species (incl. 4 BEs). Therefore, inspite of good thermals along the lakefront, an East wind diverts Broad-wingeds inland. Doug Lockrey, coordinator CMRW _______________________________________________ ONTBIRDS is presented by the Ontario Field Ornithologists - the provincial birding organization. Send bird reports to ONTBIRDS mailing list [email protected] For instructions to join or leave ONTBIRDS visit http://www.ofo.ca/ontbirdshow.htm ONTBIRDS Guidelines may be viewed at http://www.ofo.ca/ontbirdsguide.htm
