In a House committee Thursday, lawmakers voted 17-1 to direct state regulators to study the effects of wind turbine farms on migratory birds.

With one state lawmaker making bird calls as the hearing progressed, state Rep. Barbara Flynn Currie, D-Chicago, said the study could help the state determine if there are better or worse places to build wind farms in terms of how they affect avian mortality rates.

"We ought to be pretty careful where we put them," said Currie, who is sponsoring House Resolution 943. "It would be wise to know before we build them."

The legislation, backed by the Sierra Club, comes as Central Illinois is being increasingly targeted by wind farm developers as a prime location for building the giant energy producing turbines.

There are a number of major wind farm projects in the works, including one unveiled earlier this week that would put 100 wind turbines on an 8,000-acre swath of land in northwest McLean County. Another is being developed in the eastern part of the county.

Other wind farms are either located or proposed in parts of Lee, Grundy, Bureau and Livingston counties.

The growth of the alternative energy source comes in the wake of Gov. Rod Blagojevich's push to boost renewable energy usage over the next six years through the use of tax credits.

Although wind farms are viewed as an attractive alternative to coal- and gas-powered electric generation, groups like the Sierra Club also have raised concerns about birds being killed by the giant, spinning blades that capture the wind and transform it into energy for businesses and households.

A September 2005 General Accounting Office report to Congress noted that there is evidence that wind turbines kill some birds, but that the number varies by region. It said scientists have not yet drawn definitive conclusions about the effects that wind turbines have on bird and bat populations.

Currie said the study is not designed to put the brakes on wind farm construction. Rather, she said, "It just would be wise to know whether there is any effect on birds before we build the wind farms."

State Rep. Chapin Rose, R-Mahomet, cast the lone "no" vote in the House Environment and Energy Committee. He said he doesn't think the state can afford the study.

Currie did not have an estimate for what the study would cost.

The measure now heads to the full House for further debate.