Call it climate change, global warming or a conspiracy by scientists to assure long-term research work — or disagree over the whys and hows — weather patterns are changing and the effect can be seen in wildlife species.
Most of the research has been on the effects of warmer temperatures, when some species can be pushed to higher elevations or higher latitude. Another factor, however, is entering the discussion: precipitation.
Results from Oregon State University research of a 32-year period suggest that birds in western North America may be more affected by regional precipitation changes than by warming trends.
The results were published in Global Change Biology.
The study suggests that if climate change results in winters with less precipitation, there will be a spring drying effect so that populations of drought-tolerant species will expand and birds that rely heavily on moisture could decline.
Rufous hummingbirds apparently are affected by December snows and rains. The species is declining at about 3 percent a year and it may be linked to a drying trend in the Northwest.
“It makes sense when you think about it,” said ecologist Matthew Betts, an associate professor in Oregon State’s College of Forestry. “Changes in precipitation can affect plant growth, soil moisture, water storage and insect abundance and distributions.”
But temperature still appears to be the main driving force of change.
In the Eastern U.S., Carolina chickadees and black-capped chickadees, closely related backyard birds, meet and interbreed in the zone of overlap.
That zone is moving northward, movement that matches the warming winter temperatures, according to researchers from the Cornell Lab of Ornithology and Villanova University.
The hybrid zone has moved northward at a rate of 0.7 mile per year over the last decade, a relatively short time for that much avian movement.
In the Southwest, a recent study suggests that drought conditions are delaying nesting by two weeks or more for some Sonoran Desert bird species.
Delayed nesting makes it more difficult to maintain their numbers even if they if adapted to low-rainfall areas.
The research was done by Point Blue Conservation Science and the U.S. Geological Survey.
“To understand how late the delay is, it would be like if the robins nesting in your yard, who typically begin nesting in late April, did not begin to nest until nearly Memorial Day,” says Chris McCreedy, Point Blue ecologist and the study’s lead author.
The findings also show that some Sonoran Desert species sometimes forego breeding entirely during extreme drought.
This study highlights drought as a key threat to birds in arid landscapes. In the recent 2014 National State of the Birds Report, birds in arid landscapes were found to show the steepest declines, nationwide.
I offer these examples with the caveat that I am not qualified to make a judgment as to whether the protocols of any study meet scientific standards.
Columnist Sharon Wootton can be reached at 360-468-3964 or www.songandword.com.
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