[obol] Bouncing thrush maps -- addendum
- From: Joel Geier <joel.geier@xxxxxxxx>
- To: Oregon Birders OnLine <obol@xxxxxxxxxxxxx>
- Date: Tue, 29 Apr 2014 08:58:20 -0700
Hi again all,
Frittering away a bit more time on the ebird range maps for Swainson's
Thrush, I came up with an alternative explanation of the crazily
bouncing contours on the northern plains:
There are a handful of very early SWTH reports from towns in SW
Manitoba, as part of a generally sparse and strongly clustered dataset.
Kriging based on these clustered points would probably produce the same
phenomenon that I guessed was an edge effect.
A large percentage of the North Dakota spring migration records seem to
come from a few days of birding in a narrow strip along I-94 east of
Bismark in May 2007 by three birders: Tim Lenz, Chris Wood, and Peder
Svingen (perhaps a relative of Dan Svingen?). At each stop, all three
recorded exactly the same counts as separate lists, tripling the weight
of these observations.
It's no wonder that the maps come out a little goofy, after feeding
these data into a mathematical smoothing algorithm.
Happy birding,
Joel
--
Joel Geier
Camp Adair area north of Corvallis
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