Date: 3/9/17 7:51 am
From: Dennis Vroman <dpvroman...>
Subject: [obol] Re: Theory About the Role of Predators in Invasive Species Control
Have seen Cooper's Hawks take Collared Doves. Dennis

----- Original Message -----
From: <Bigrocketman...>
To: <obol...>
Sent: Wednesday, March 08, 2017 7:06 PM
Subject: [obol] Theory About the Role of Predators in Invasive Species
Control


>
>
> It was an interesting suggestion by Frank Kolwicz, that a decline in
> Eurasian Collared Dove populations might be due to Sharp-shinned and
> Cooper's Hawks learning to focus on them. They are larger than Mourning
> Doves, fly more slowly and with less dodging around in their flight-paths.
> They don't seem nearly as wary or as inclined to instantly flee, at the
> first hint of danger. And they have a habit of sitting out in the open, on
> poles. The hawks may have gradually developed an appreciation for the
> potential they offered and begun seeking out that species.
>
> I have a similar theory about the major decline in opossum and nutria
> populations in Oregon during the last three decades. You don't see nearly
> as many of either as you did during the '60s and '70s. I think that a main
> factor could be that the predators, such as foxes, coyotes, bobcats and
> cougars, gradually learned what a good and easily-taken food-source they
> were. They developed abilities, through several generations, about where
> to find and how to catch them. Another factor of course, is the role motor
> vehicles play in opossum control. The depletion of ground-nesting birds by
> the earlier opossums and the awareness of gardeners near watercourses,
> about the need to fence and protect their crops, also played a part.
> Fences have to be deeply extended underground, to keep out the burrowing
> nutria. In some places, they were worse than deer for eating all your
> vegetables. There's many foxes and coyotes near where I live and an
> occasional bobcat or cougar. Along streams where I once
> saw dozens of nutria, there was only one this year and then, it was also
> gone.
>
> Steve McDonald
>
> http://www.ipernity.com/home/305883
> http://flickr.com/photos/22121562@N00/
> http://www.vimeo.com/user458315/videos
> https://onedrive.live.com/?cid=229807ce52dd4fe0
>
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