[obol] Bird migration timing and global climate change

[Don Baccus]

On Apr 19, 2008, at 10:50 PM, DAVID IRONS wrote:
>  If current trends continue, not every corner of the globe will be  
> warmer, in fact some might be quite cooler.  Global climate change  
> is accurate, global warming is not.

Global warming, in climate science, refers to the *average* global  
temperature, and within the field has never been used to argue that  
every point on the globe will warm.

So it's an accurate term as used by professionals, who have never  
claimed that every point on the globe will warm.

But "climate change" is replacing "global warming" in the vernacular,  
and perhaps even professionally, though many climate scientists still  
refer to AGW because it's accurate, accepted, and professionals don't  
like changing their vocabulary simply because it's misunderstood by  
laypeople.

> Anectdotal human observations are inherently biased by the prior  
> knowledge, experiences and the expectations of the observer.   
> Generally speaking, reports of birds on OBOL fall into this category.

I won't disagree with this, and it's true for most of the united  
states, which is a young country which has experienced rapid growth,  
especially here in the West in which populations have exploded since  
WW II.

And the introduction of binoculars, bird books, in general more  
leisure time, the automobile all introduce confounding factors.

However there are parts of the world with much longer records of  
events that are easier to observe accurately, for instance average  
first bloom of plants in gardens kept for decades or (in the case of  
many state/royal gardens in europe) centuries.

They don't migrate, they're planted.  They're not hard to find,  
identify, and British gardeners are often tenacious recordkeepers.

So there is good anecdotal evidence (that's not all), but overally I'd  
agree that bird arrival times in the western united states probably  
aren't going to be a good source.

Just to give an example, in the raptor banding work I've done in the  
intermountain west, our band recovery rate is a bit under 1%.   Band  
recovery rates for roughly the same mix of species (read "mostly  
sharpshins, kestrels, and coops") is around 5%.

It's largely a function of population density and accessibility (most  
great basin mountain ranges are rarely visited by people, as road  
access, even 4WD tracks, are relatively rare, and when they are  
visited, only a few portions are readily accessible even on horseback).

So in a huge chunk of the intermountain west, in many ways the most  
interesting for migrants (forested mountains), are never visited.

Hard to build a decent picture facing that restriction ...


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