Saturday, December 12, 2009

Warbler Guy, have wood-warblers shifted their winter distribution as warmer winter temperatures have become more common in recent years?

(Above, thanks to Martin Meyers for submitting a Common Yellowthroat male photo (taken in Nevada) )

That’s a fine question, Howie (in Minneapolis).

Turns out the answer is “yes,” if you agree with a recent technical report titled “Birds and Climate Technical Report (Niven, Bucher, and Bancroft, 2009;

This report tracked the locations of 305 species by using Audubon Christmas Bird Count (CBC) data collected in the past 40 years throughout the lower 48 states (and s. Alaska and s. Canada).

Among these species, researchers suggest 58% of them shifted farther north in the past 40 years. They include many non-warblers such as Fox Sparrow, Pileated Woodpecker, Pine Siskin, Purple Finch, Ring-Billed Gull, and Fox Sparrow, among others.

Which wood-warbler species has shifted father northward during winter? It’s the Common Yellowthroat. Seeing this moisture-centric species on CBCs is not uncommon during the breeding season, especially because they are found throughout all of the lower 48 continental states. In addition, even seeing them throughout the winter in southern states is regular occurrence.

More eyebrow-raising: Seeing them increase their presence in northern USA states when the December/January CBC surveys occur. By this time, insect resources should have ebbed. Resources are few and far between. The pantry is empty for most insect-dependent bird species, such as Yellowthroats.

In other words, a sighting of a Common Yellowthroat on an Illinois or Indiana (or Wisconsin) CBC used to be much more rare. But the current report suggests the shift northward has made a winter-time Yellowthroat observation less rare.

The authors of the report cite four lines of evidence as verification of warming climate being a major factor in why bird species’ (including the Yellowthroat’s) have shifted north during the last 40 winters.

Time and space doesn’t allow me to discuss these four areas. But it’s worth noting that the birds’ movement north is consistent with computer model predictions based on a hypothesis of global warming/climate-change effects, according to the authors’ contention.

To read more about this report, see:


Anonymous said...

I think Palm Warbler would also be affected global warming, too. With N. England warmer in winter, then Palm shows up more in Nov./Dec./Jan. and beyond during some years.

I may be wrong. But seems logical.

Jesse W.

Anonymous said...

Thanks a bunch for the info.

Anonymous said...

I'll bet other warblers are negatively affected by a warmer earth that people are helping make a true reality.

Just my 2 cents....Felicia Armstrong, Phoenix, AZ

Anonymous said...

I think that I see warblers a week or two earlier in some cases than in the 50s and 60s.

Just my two cents that Global Warming is true.


LeRoy Neeman, Topeka, KS

Mary said...

I found your site while trying to determine what the new bird at my suet feeder is. It seems like it *must* be a female Wilson's warbler though, according to Sibley, such a bird has no business in Seattle in early January. Are Wilsons another warbler showing up farther north than it belongs in the winter? (It certainly seems contented enough in my backyard!)

Anonymous said...

Wilson's is rare to uncommon (to absent) in WA in January, but I don't doubt that you saw one of the brave individuals that remained (and did NOT migrate).

To further answer your question from the 1/9/10 comment you left, above, I don't think there's a trend that documents Wilson's Warbler showing up more often. But the Christmas Bird Count totals/diversity for the last few years would be the only surveys that probably would best assess any trend, if one exists.

Of course, the CBC is not a full-proof, peer-reviewed, rigorous/academic designed survey. It would be considered bias by many scientists. That said, it's the only long-term one we have for the non-breeding season, given the CBC began in 1900.

Nonetheless, in sum, any checklist for your area will verify that Wilson's is rare to absent in Jan.

Regards, Daniel, Warbler Guy :-)

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