Robins in winter not a happy sight

The American robin, long a welcome sign of spring on the Front Range, has become a harbinger of something more worrisome: global warming.

Rising temperatures have caused the red-breasted birds to stay in Colorado all winter, according to a report released Tuesday by the National Audubon Society.

The report, which draws on 40 years of data the society has compiled during Christmas bird counts, said the number of robins wintering in Colorado has increased 1,704 percent since 1968.

This week, several flocks of robins were spotted throughout the foothills west of Colorado Springs.

"Birds are showing us how the heavy hand of humanity is tipping the balance of nature and causing ecological disruption in ways we are just beginning to predict and comprehend," said Greg Butcher, Audubon director of bird conservation.

The nonprofit advocacy group's study found that 58 percent of the 305 widespread bird species that winter in North America have shifted significantly north since 1968, some by hundreds of miles.

Data showed robins' winter range shifted 206 miles - which means robins that once wintered in Texas now can be seen in Monument.

Other Colorado species, including magpies and wood ducks, have seen similar shifts north.

Many factors may account for the increase in robin sightings in Colorado. Small numbers of the birds have always wintered on the Front Range. A shift in regional land use from grasslands, where robins don't typically live, to suburban yards, where they do, might explain part of the increase.

However, other studies seem to back the theory of widespread warming. Colorado's few remaining glaciers are in fast retreat. Treeline is slowly creeping higher. Lakes where pioneers once harvested ice now rarely freeze. And the average temperature in Colorado Springs for the last decade was more than half a degree higher than during the 1950s, according to National Weather Service data.

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Contact the writer: 636-0223 or dave.philipps@gazette.com