On Feb 9, 2011, at 12:52 AM, Michael Price wrote:

> If the Barred Owl were a fish, it would be the equivalent of the invasive snakefish which is currently hoovering up many of the indigenous species in the Mississippi watershed.

Except the snakefish ("Fishzilla"!) is an Old World exotic introduced by a humans and is clearly invasive with impacts on multiple (distinct) species and no predators.

http://en.wikipedia.org/wiki/Snakehead_%28fish%29
http://www.smithsonianmag.com/science-nature/snakeheads.html

But the Barred Owl is a range-expanding native of the US. Is the Barred Owl an invasive species?

Take a look at "Invasive Species Definition Clarification and Guidance White Paper" to get a feel for the regulatory definition in the USA (which is what counts for the Spotted/Barred Owl problem)

http://www.invasivespeciesinfo.gov/docs/council/isacdef.pdf

Is the Barred Owl native in this ecosystem by this definition? I can see people arguing it both ways: it is a gray area. I think it is it arrived under it's own power but others could say the spread is human caused.

Is there any evidence for a direct anthropogenic cause for the western range expansion of the Barred Owl in Canada? Saying "LOGGING" isn't enough, Barry. What was the historical range of the Barred Owl? How has it changed with time?

Another thing to keep in mind with the Barred Owl and Spotted Owl is that they hybridize and the hybrids are fertile. Both F1 and F2 hybrids have been identified in the wild and the F1 hybrids have bred with both Spotted and Barred Owls. So genetically they aren't that far apart.

http://www.sei.org/owl/meetings/Presentations/December/Kelly.pdf

So are the two species in contact again after a period of geographic isolation (like the Hermit Warbler and Townsend Warbler and their hybrids in the contact zone). Did the Barred and Spotted Owls speciate after separation during a glaciation period as the subspecies of the Spotted Owl have been shown to have split 120,000 and 15,000 years ago? I've not found a paper on the phylogeography of the Barred Owl but it's worth considering in the "normal expansion" versus "not normal expansion" because time scale matters. If the two groups are relaxing back to their former state the case for extensive management to stop the two group merging together is pointless.

This perhaps ends up being a problem not just of "plot size" but of time scale too: which particular time point do you wish to conserve and how much effort are you going to put in to conserve it.
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Kevin Purcell (Capitol Hill, Seattle, WA)
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