Date: 9/20/19 5:15 am
From: Merrily Hart <merrilyhart...>
Subject: Re: [birders] Saturday Lake Erie Hawk Watch
What are Chances for a good day of movement today?
Merrily Hart
Ann Arbor

Merrily Hart
Sent from my iPhone

> On Sep 20, 2019, at 7:52 AM, Mark W <markwloch72...> wrote:
>
> 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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> <BWHawk Data1991-2008.jpg>

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