Date: 9/20/19 4:51 am
From: Mark W <markwloch72...>
Subject: Re: [birders] Saturday Lake Erie Hawk Watch
I attached an image of Detroit River Hawk Count Broad-winged (BW) Hawk
data from 1991-2008 that I found online ten years ago. The data shows that
on average, the BWs push through in an extremely tight window, with 81%
passing between September 15-20. Those numbers of course are a bit skewed
by the massive 100k plus days that have only occurred on Sept. 17, 18 or
19. That being said there was a day with 30,000 that happened as late as
September 26. So calendar-wise a really good day may not be likely but is
still possible.

Now for the weather factor. North winds push the Ontario birds down to
the north shores of Lake Erie and Ontario, which are road blocks to the
thermal-seeking hawks, so they follow the shoreline until they cross at the
relatively narrow Detroit River. If weather for whole region had been
rainy along the upstream (Ontario) migration route during the tight window
mentioned previously, you could figure that maybe they hadn't pushed
through yet. But the past few days have been dry with partly to mostly
sunny skies that produced migration friendly thermals for the birds to ride
on. Numbers at LEMP this week were good on the 16th(34k) and 17th(23k)
when the winds had a northerly component but dropped off later in the week
as southerly winds took over. After Tuesday the southerly winds most likely
pushed the birds away from Lakes Erie and Ontario, so the set up for a big
day doesn't seem to exist. And even if it did, the southwest winds in
Saturday's forecast would most likely push them north of LEMP.

Note : This is just an opinion and birds don't look at data or weather
forecasts.

Mark Wloch
Ludington, MI




On Thu, Sep 19, 2019 at 11:20 PM Patrick Baize <pkbaize...>
wrote:

>
> I know there's no guarantee for birds but does anyone have any thoughts
> for Saturday.
> Pat B. Howell, Michigan
>
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