Rarely does one get the opportunity to track hawks [unless they have
satellite transponders]. Rare species and dark morphs present one
opportunity to do so.
At the Sunday Sept 19 Burwell Provincial Park hawk watch, a dark morph
Broad-winged Hawk passed over us at 10:50 a.m. We noted the time just as it
passed over head in a rather low glide. Only 40 minutes later at 11:30
a.m., the watchers at Hawk Cliff also saw a dark morph Broad-winged Hawk.
[Hawk Cliff is west of Port Burwell].
The straight line distance from our hawk watch location in Port Burwell PP
is 28.5 km from Hawk Cliff Road [as measured on a topographic map].
Assuming the birds we saw were the same, and they likely were given the
rarity of this morph [our first], this bird was averaging between 40 and 45
km/hr.
When in glide mode, it's likely that Broad-wings are travelling much
faster, perhaps as much as 100 km/hr. Given its low elevation when it
passed over us, this bird must have kettled at least once and possibly a
couple of more times between Burwell and Hawk Cliff. When birds are
kettling they are generally not moving very far or very fast in the
direction they are travelling, so the 40 to 45 km/hr is the average forward
motion of this bird. Later in the day, when the thermals are rising even
higher, hawks have to kettle less and less because they can rise higher and
higher and likely travel great distances at great speeds between having to
kettle, if at all. As hawk watchers know the Broad-wings often get so high
by noon they are extremely hard to detect, especially on a cloudless day.
Alan Wormington and I experienced this frustrating phenomena in Essex
County on Saturday morning. He was watching hawk migration at his Seacliff
site. At the same time, I was about 10 km inland at a station near
Blytheswood on Hwy 77. His Broad-wing total for the morning was just over
400 birds and mine was 61 birds. Yet, as you know from reading the hawk
reports for that day, Holiday Beach recorded nearly 20,000 and Erie
Metropark recorded 130,000 birds [albeit both of these sites counted all
day whereas we only counted from 0900 to 1200]. However, in each half hour
of our count, the number of hawks diminished. Even if we hadn't planned to
stop at noon we would have anyway, as the number of hawks had diminished to
the point where we would have given up. This leaves many questions of
course. Where had the birds started that day? Were the "TUVs" already so
strong early in the morning that they rose high enough not to be seen when
they passed over us if they did? Why do they descend low enough to be seen
at Holiday Beach and Erie Metropark? Is there some other unknown flight
path through Essex County?
Dave Martin
[EMAIL PROTECTED]
Harrietsville, ON
