Warmer Winters and Birds

Red-bellied Woodpeckers are increasingly found at backyard feeders in northeastern North America.
Red-bellied woodpeckers are increasingly found at backyard feeders in northeastern North America. Jim Utton/All Canada Photos/Getty Images

In eastern North America, the end of the year 2015 was characterized by unusually mild weather. Numerous warmth records were broken all across the region, and some December nights were more typical of a late spring or early summer night. It is a weather pattern consistent with the ongoing El Niño conditions, in addition to the incremental warming and increased variability associated with global climate change.

How Are the Birds Responding?

Many of us have notice birds lingering longer into the cold season. A quick look at the Cornell University’s citizen science platform eBird for the Ithaca, New York area reveals December sightings of Eastern Bluebird, American Robin, Northern Flicker, and Song Sparrow. Those are all species we associate more with Memorial Day than with Christmas. Has there truly been a change in the wintering bird community in temperate latitudes?

Citizen Science at Work

Researchers at the University of Wisconsin-Madison examined that very question. They used data from Project FeederWatch, another citizen science program, to look at how bird communities have been changing over time at people’s backyard feeders. From the data provided by over 30,000 FeederWatch participants, they found evidence that for a period of 22 years the winter bird community has shifted to include more warm-adapted species.

The phenomenon is global: other studies have found similar patterns in Europe. In the northeast US, the species most responsible for these shifts included the Purple Finch, Carolina Wren, Red-bellied Woodpecker, and Eastern Bluebird.

It appears that the most important driver of this change in community is a northward shift in many species’ geographic range.

It might be tempting to credit this change to the popularity of bird feeders, but the number of people feeding wild birds (around 53 million in the US) has not increased since 1991. The study’s authors conclude that “a shifting winter climate has provided an opportunity for smaller, southerly distributed species to colonize new regions and promote the formation of unique winter bird assemblages throughout eastern North America”.

More Concerns for Spring Migration?

Winter warm ups like those we are experiencing with increasing frequency probably do not affect birds negatively. They are very mobile animals able to track down the resources they need to survive, and the warmer days may help them do that in the shorter term.  

When it comes to global climate change and birds, scientists are more worried about a different phenomenon. The concern is centered on the timing of seasonal events, a concept called phenology. Global warming is shifting many of these events earlier in the spring: trees leafing out, plants flowering. However, not all the members of an ecosystem adjust at the same speed. For example, while birds have evolved to arrive in spring in time to nest just at the peak in caterpillar abundance, now they may be arriving after that peak, threatening their ability to raise young.

This problem, called phenological mismatch, is yet another stressor for bird populations already at risk of extinction.

Source

Princé, K. and B. Zuckerberg. 2014. Climate Change in Our Backyard: the Reshuffling of North America’s Winter Bird Communities. Global Change Biology.

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Beaudry, Frederic. "Warmer Winters and Birds." ThoughtCo, Mar. 7, 2017, thoughtco.com/warmer-winters-and-birds-1203614. Beaudry, Frederic. (2017, March 7). Warmer Winters and Birds. Retrieved from https://www.thoughtco.com/warmer-winters-and-birds-1203614 Beaudry, Frederic. "Warmer Winters and Birds." ThoughtCo. https://www.thoughtco.com/warmer-winters-and-birds-1203614 (accessed November 21, 2017).