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Interesting discussion.
Of the owls I'm most familiar with, only the Boreal is known to stop
calling once nesting has commenced. I do not know if anyone has followed
nesting Barred Owls, for example, and recorded calling rates prior to, and
after the commencement of nesting.
One year, I had a Saw-whet calling quite late, even during the daytime. My
impression was he was the nerd of the Saw-whet world, and the ladies
weren't too impressed with him! Eventually though, I found the cavity from
which he was calling (not an easy task with one ear not working well) and
later, he and a lovely young lady raised one young. The daytime calling
stopped, and I think the night time calling went down significantly.
Surveys which use many people, whether volunteers or paid, have
many inherent difficulties. We're all using the same soundtracks, but not
all the same players and speakers. We don't all have the same ability at
(a) hearing or (b) identifying the owls. Estimating the distance from which
an owl is calling (is it facing you, or facing away...is the sound coming
through the woods or across a field, is there wind? run off noise?) can be
daunting. Large numbers of replicates (many routes, many stations, many
years), tend to smooth out some of the bumps, but the data must still be
used with caution.
Randy
_________________________________
RF Lauff
Way in the boonies of
Antigonish County, NS.
On 17 April 2013 09:10, Ronald Arsenault <rongarsenault@gmail.com> wrote:
> Hello Patricia,
>
> Very interesting question and one to which I do not know the answer. I
> should also point out that the sentence which prompted your question was my
> interpretation of what Scott had said, so I will attempt to clarify.
> Please note that this is based on a conversation which happened three to
> four years ago.
>
> As I recall, Scott found during his monitoring that owls were less vocal
> when tending nests with eggs or young than was the case during years when
> they did not nest or the nesting was not successful. His concern was that
> the results of the owl survey were being (or would be) interpreted as "more
> calls = more birds", which his monitoring showed was not the case.
>
> At the time, his intent was to discuss his findings with Bird Studies
> Canada to make them aware of his concern. I do not know what eventually
> happened. Perhaps the "silent listening" was implemented as a result?
>
> I do not recall Scott going into detail re owl behaviours that would
> explain this. I would suggest though, that there are a number of factors
> which are likely to affect the calling rate, including the response rate to
> playback, of owls. However, I would not expect complete suppression except
> for cases of severe starvation. Some factors which likely affect the
> calling rate of owls (with or without stimulation by playback) are: timing
> - how far into the nesting season are the owls when the survey is done;
> whether or not the bird is paired - single birds would be more motivated to
> call; prey density - more time needed to catch enough prey = less time for
> calling; distance from nest - the closer the playback to the nest, the
> likelier the response; density of the owl population could even play a
> role; perhaps even the age of the birds could also be a factor - well
> established pair vs first time nesters?. These are just some of the factors
> which come to mind, and of course, these are not necessarily independent of
> each other. Perhaps others (Randy?) can add to or correct the above.
>
> Hope this helps,
>
> Ron
>
>
> On Tue, Apr 16, 2013 at 10:56 PM, P.L. Chalmers <
> plchalmers@ns.sympatico.ca> wrote:
>
>> Hi Ron,
>>
>> ** **This is an interesting observation. But it leaves me with a
>> question. Are "owls which have settled down with nesting duties" less
>> likely to call AT ALL, or just less likely to respond to a recording? The
>> ":silent listening" portion of the survey, which is the first part,
>> preceding the broadcast of recorded calls, is considered the most
>> significant part of the survey, I believe. {In some parts of the country
>> the official survey protocol doesn't use broadcast calls at all.) So are
>> owls which are freely calling, i.e. when unprovoked, more likely to be
>> unsuccessful breeders than those who remain silent?
>>
>> ** ** Suzanne Borkowski and I usually detect many of the owls we
>> find during those first two minutes of the survey; if they react to the
>> broadcast calls later, it gives us more time to confirm distance and
>> direction etc.
>>
>> ** **Cheers,
>>
>> ** **Patricia L. Chalmers
>> ** **Halifax
>>
>> ** **
>>
>>
>> At 02:16 PM 16/04/2013, you wrote:
>>
>> Hello Randy,
>>
>> This may in fact be good news. Scott Makepeace, NB Dept. Nat. Resources
>> biologist who monitors owls, told me that his work has revealed that the
>> response rate of owls is actually inversely related to their nesting
>> success, especially with Barred Owls, if I remember correctly. In other
>> words, owls which have settled down with nesting duties are much less
>> likely to respond to a taped call than are owls who are either looking for
>> a mate or whose nesting attempt has failed.
>>
>> Hope this cheers you up!
>>
>> Ron
>>
>>
>> On Tue, Apr 16, 2013 at 11:30 AM, Randy Lauff <randy.lauff@gmail.com>
>> wrote:
>>
>> Krista and I did the Fairmont (Ant. Coi.) route last night. Frogs were
>> barely an issue as it was about -3 oC the whole time. Three or four years
>> ago, I got a dozen (?) or so Barreds, GHOW and S'whets. Last year, skunked.
>> This year, under similarly ideal conditions as last year...skunked. Very
>> perplexing.
>>
>> Randy
>>
>> _________________________________
>> RF Lauff
>> Way in the boonies of
>> Antigonish County, NS.
>>
>>
>> On 16 April 2013 01:13, James Hirtle <jrhbirder@hotmail.com> wrote:
>>
>> An interesting evening for running this route with owls on 8 out of 10
>> stops. We missed out on owls interestingly on two of the stops that we
>> usually get them. One of these stops now has a trailer at the location, so
>> that could be the reason. The other stop we always have wood frogs and
>> spring peepers so loud that i