[obol] Bird migration timing and global climate change

[Don Baccus]

On Apr 20, 2008, at 8:55 AM, Joel Geier wrote:
>
> The most rigorous, relevant data come from banding stations, hawk
> watches, or other types of systematic surveys that sample the entire
> progress of migration, in a given, fixed location each year. In our
> region, most such surveys have only recently been established, but
> biologists in other parts of the world (for example Britain and  
> Sweden,
> have accrued a much longer record of systematic observations, going  
> back
> at least to the time of Linnaeus.

We've got about 30 years at two sites in the intermountain west, the  
Goshute Range in eastern Nevada and the Wellsville Mountains in  
western Utah (the two flank the Great Salt Desert).  These have been  
nearly constant-effort counts (i.e. same hours, two counters, year  
after year, from late summer to late fall with a few exceptions due to  
exceptionally early snowfall, illness of crew or lack of money causing  
part or all of a few seasons being conducted by one person, etc).

There's also weather variability to consider, and mountains tend to  
have somewhat high variability in the extremes (particularly in the  
direction of bad weather making observation impossible).  Along with  
counts being shut down due to early snow (these are pack-in sites with  
limited logistical support, safety of crew comes first), we've had  
years when the typical peak period has seen extended rainfall or fog,  
or conversely fine weather with east winds that tends to keep the  
birds to the west or very high overhead beyond binocular view (there  
have been radar studies in the east which are a bit depressing in that  
regard).

That's probably about a lower limit for looking for a signal.  AFAIK  
thus far no one's tried to analyze the data for this purpose.  I think  
you'd need a large shift in peak migration time to be able to compute  
a statistically valid trend due to the high variability of the data  
due to the factors I mention above.  Sharpshins and kestrels would be  
the best bet due to the fact that they migrate early (thus bad weather  
is less of a factor than with later migrants - kestrels peak in early  
september) and are seen in large numbers at the two types (thousands).

In the east, of course, we have count records at Hawk Mountain that go  
back nearly 80 years.

But we have nothing at all like the data available in Europe.

> However, it's different in other parts of the world such as Japan,
> China, and Europe. Consider those storks that I saw on Thursday  
> evening

Sidenote: Joel, all the time you spend in Europe, and you've never  
seen storks before?  :)

>
> If we want to try to expand Oregon's contribution to this body of
> knowledge, we should consider which migrant birds figure most
> prominently in our current "folk culture." We probably shouldn't focus
> on birds that are practically invisible, like Hammond's Flycatchers.

I should think the focus should be on common birds that have not been  
neither too negatively or positively impacted by habitat changes due  
to agriculture, urbanization, etc.
>
> How long has the practice of keeping hummingbird feeders been  
> popular? I
> know they've been around all of my conscious lifetime (at least back  
> to
> 1965). It might be profitable to seek out records of people who have
> kept hummingbird feeders over the decades.

Seems like a good choice, yes.


----
Don Baccus
http://donb.photo.net
http://birdnotes.net
http://openacs.org