I would be hesitant to attribute behavior across the board from songbirds to
owls and have independently come to conclusions similar to what Jamie Acker
describes. To put it simply, after a long, hard breeding season, with
dispersal the adult owls are now free to re-establish and maintain
territorial boundaries. Barred Owls are naturally aggressive and I have been
hit or grazed numerous times at all times of year. If the owls are more
actively concerned with territorial integrity, it makes sense that there
might be more instances of aggression. Another point to consider is that I
find all the large owls more vocal this time of year, and would include
Saw-whet Owls, but if it were due to length of day related to breeding, I
would think this effect would be staggered to match their breeding time. If
this is the case, it's not obvious from my data.

(Saw-whet Owls are a special case in that some owls migrate in the late
summer and early fall. Although most information about Saw-whet Owls state
that they are heard almost exclusively during breeding season, I actually
hear more Saw-whet Owls this time of year while performing surveys. However,
the "toot" calls in the early part of the year are replaced by mostly
"skiew" calls this time of year. I think this is more likely aligned with
migrational behavior, whether an owl actually migrates or not, than it is a
return of breeding behavior.)

It may also be that with dispersal and the young owls moving among
established territories, there is a need to re-enforce boundaries and let
the young owls know where they can and can't go. I have over 300 Barred Owl
pair sites in my area, and if a conservative 1 juvenile dispersed per pair
per year is used, that would be 300 new owls all moving around this time of
year. Add to that Great Horned and Spotted owl juveniles, and that is a lot
of new activity for large owls, with the owls all looking for some place to
spend the winter. This could also affect "floater" owls, those adults
without an established territory hanging out in the background, possibly
causing them to move around and jockey for position as well. There is great
change in owl population dynamics this time of year.

Length of day may have some triggering effect on owl behavior but it doesn't
appear to me to be the necessarily the same as it may affect some songbirds.

Bob Pearson
Packwood, WA


Message: 1
Date: Mon, 21 Sep 2015 12:16:29 -0700
From: Joshua Glant <josh.n.glant at gmail.com>
Subject: Re: [Tweeters] Owl attack, why now?
To: Michelle Landis <asmalllife at gmail.com>
Cc: Tweeters <tweeters at u.washington.edu>
Message-ID: <06C9E633-9330-4F02-A3A6-C3D57B8AA47C at gmail.com>
Content-Type: text/plain; charset="us-ascii"

Yes! I think that's it! The twenty-dollar answer! Thank you!

"You've won a trip to... Neah Bay!" (Or Hawaii, if you're into that sort of
thing.) :)

Thanks and good birding, Joshua Glant


> On Sep 21, 2015, at 8:45 AM, Michelle Landis <asmalllife at gmail.com> wrote:
>
> I think it's 'recrudescence', spelling is probably off. :)
>
>> On Sun, Sep 20, 2015 at 2:18 PM, Joshua Glant <josh.n.glant at gmail.com>
wrote:
>> Thanks for bringing this up! I was going to mention it myself, but I
>> didn't want to appear ignorant by linking two phenomena that weren't
>> related... :)
>>
>> I've been hearing Robins, a Varied Thrush and even a Townsend's Warbler
sing in the past week! I believe I read somewhere that there is a specific
name for this photoperiod-related behavior, but I haven't found it yet.
>>
>> I don't believe that the Anna's Hummingbirds quite fit into this
phenomenon (they're territorial throughout the season), but I could be
wrong. Who says hummingbirds are exempt, anyways?
>> Good birding, Joshua Glant
>>
>> Mercer Island, WA
>>
>> Josh.n.glant at gmail.com
>>
>>
>>
>>> On Sep 20, 2015, at 1:17 PM, Bud Anderson <falconresearch at gmail.com>
wrote:
>>>
>>> "False spring" near the fall equinox elicits a mirror image pulse of
spring breeding behavior among many bird species. Same length of day/night
as spring.
>>> Listen for courtship calls, copulation, pairing up for awhile. Probably
most easily viewed in starling behavior.


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