[obol] Thoughts On Snowy Owl Irruptions and Migration

[Cindy Ashy]

It is always interesting on OBOL to read about trends
observed by people like Tim R. who have decades of
data from one location. Obviously, birds are not
studying NOAA charts to plan their migrations and they
are not responding to weather cues at their final
destination. However, there is so much we don't know
about what causes weather patterns, especially at
mesoscales, I wonder if birds are actually responding
to something correlated to weather patterns (and not
the weather itself) that we just don't yet understand
like magnetic field shifts.

We know from the behavior of captive birds that are
not exposed to certain types of natural environmental
stimuli that the primary factor for when to migrate,
at least for many species, is not weather related. We
hear about caged migratory birds inside dark
temperature controlled rooms repeatedly flying/banging
themselves against their cage in the direction they
would be migrating if they were in the wild. It seems
most people think that the primary factor on when to
migrate is intrinsic, perhaps hormonally driven, and
that weather fine-tunes this. However, I wonder if
it's actually environmental factors that we don't yet
understand that serve as the primary trigger (but
still hormonally driven). I wish some ambitious grad
student would compile the data (where reliable) from
captive bird sites to take a closer look at this
(maybe this has already been done?). The factors
captive birds were exposed to would need to be teased
out by site. For example, some captive birds may be
exposed to natural daylength changes but not natural
temperature changes and so on.

Related to the mysteries of migrations in my mind are
the mysteries of Snowy Owl irruptions.

Sometimes I can't help it and I lament about missing
the Snowy Owl in Newport.  When I do people invariably
remind me that we get Snowy Owls at the mouth of the
Columbia River about every 4 years and a major
irruption further south about every 10-12 years which
of course leads to the discussion of what causes those
major irruptions. We all know the textbook paradigm
about lemming populations crashing to be largely false
so I find it a fun mystery to contemplate.  It struck
me one day that the 10-12 year interval corresponded
to the solar cycle and I googled around for a long
time one night trying to find some research on this.
Surprisingly, after searching in various ways, I
couldn't find anything solid. So, I next searched for
a reference to tell me when all the major Snowy Owl
irruptions had occurred. Mike P.'s site had the best
list I could find and he lists the "major events that
no one argues about for the West Coast" as:

1897, 1916, 1947, 1955, 1966, 1973, 1977, 1984, 1996,
and 2005
(http://home.pacifier.com/~neawanna/SNOW/SNOW_FAQ.html).


Next, I found this nice solar cycle chart at:
http://www.spacew.com/swim/bigstorm.html. 

Now, I had always assumed that geomagnetic storms were
more severe and more frequent at the top of each solar
cycle (more sunspots) and I hypothesized that there
might be a correlation between Snowy Owl irruptions
and periods of intense geomagnetic storms. Well, I got
surprised in two ways:

1. The last 7 major Snowy Owl irruptions on the West
Coast were all found at the BOTTOM of the solar cycle
(fewest sunspots). So, there does seem to be a
correlation between major irruptions and the solar
cycle but opposite from what I expected (and I've had
all kinds of wild and crazy theories as to why but not
sure if I'm ready to post those to OBOL).

2. Although there is a significant increase in
geomagnetic storms at the top of the cycle, this trend
is not as strong as I had assumed, i.e. there are
major geomagnetic storms throughout the entire cycle
and more evenly distributed than I expected. However,
the resolution of the chart cited above makes it
difficult to see exactly what's going on.

I would like to hear from OBOLers what you think about
the above correlation after you compare the dates of
irruptions and the solar cycle chart. I would also
like to point out that 1947 was a major exception
(1897 and 1916 was not on the chart). Not only did
this irruption not occur at the bottom of a cycle, it
occured at the very top of a cycle -- but keep in mind
that this was followed by 7 consecutive major
irruptions occuring at the bottom of the cycle.

I have been intending to ferret this out some more but
with the civil rights/legal issues I'm currently
dealing with I just haven't had time. I'd like to find
a much more detailed solar cycle chart (stretch out
that horizontal axis and also add some older cycles)
and take a closer look at the geomagnetic storms so if
anyone knows of a good one, please let me know. I'd
also like to know more about phenomenon that might be
affected by/correlated with sunspots that Snowy Owls
could be responding to. Was there anything special
about the 1947 irruption that could explain the big
deviation? Maybe there really was a lemming population
crash that year! I'd also like to find some info about
major irruptions in other areas of the world to
compare to the solar cycle....and I'd like to know
where Mike P. got his major irruption years from.

Anyway, please let me know what you think. How would
we entertain ourselves without our mysteries to
ponder?

Cindy Ashy


     
____________________________________________________________________________________
Be a better friend, newshound, and 
know-it-all with Yahoo! Mobile.  Try it now.  http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ


      ____________________________________________________________________________________
Be a better friend, newshound, and 
know-it-all with Yahoo! Mobile.  Try it now.  http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ