Date: 12/30/18 9:19 am
From: <clearwater...>
Subject: [obol] Re: Winter Barn Swallow in Central Oregon
In addition to the Barn Swallows recorded on the Antone CBC near Dayville (4 birds on Dec 21, 2004), one was found on the Madras CBC last year.

Certainly there may be any number of factors, not directly linked to anthropogenic climate change, that could cause a Barn Swallow or other swallow species to wander north in winter. Dave and Lars mentioned a few such causes.

But once a swallow ends up in central Oregon in winter, it needs to be finding food, or the chances of it staying alive and non-torpid long enough to be observed are scant.

Availability of flying insects is linked to local temperatures. When there are more winter days with temperatures well above freezing, that has to be helpful to swallows that have wound up -- for whatever reason -- far north of their normal winter range.

If a swallow manages to find a spot with thermal input (such as sewage treatment ponds), that might help also it to find enough food to survive through minor cold spells. The idea of "urban heat islands" that was often trotted out by climate-change skeptics a couple of decades ago (including here on OBOL) might have some relevance for winter swallows, even if it was a red herring when applied to the issue of mean global temperatures.

But swallows still need to move between those "islands" with better food availability. It stands to reason that they can do this successfully, more frequently, as average winter temperatures tend to become milder.

--
Joel Geier
Camp Adair area north of Corvallis


 
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