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Migrating Birds Slow To Return

By Staff | Feb 28, 2008

DES MOINES – The sweet voice of a male cardinal danced through the calm air searching for a willing female to answer to his spring breeding song. With a temperature of minus-2 degrees and forecasts for it to get colder, spring may seem like a far off dream.

But spring is coming and the evidence lies with the bald eagles and red-tailed hawks that are starting to build nests, and lapland longspurs, that normally over winter in southern Iowa and northern Missouri but were pushed further south, are starting to return.

“We are not seeing as many birds back as we would normally given the depth and extent of the heavy winter, but we are seeing a few robins and bluebirds,” said Doug Harr, coordinator of the DNR’s wildlife diversity program. “We are starting to see more flocks now, indicating the birds are on the move.”

Bird migration is triggered by day length, not by temperature. Day length is also responsible for releasing the hormones that tells the birds it’s time to look for a mate.

“Bluebirds and robins go only as far south as they need to and they tend to be some of the earliest to return, to push the limits because they can feed on berries and seeds. But even that supply has been limited this year,” Harr said.

That’s not the case for birds that feed on insects. There are not many mosquitoes or flies available in February, especially this year, and the way it’s going, it may be June before the insect-eaters return.