It's not often that bird food needs approval by a congressional conference committee and the president of the United States, but here we are.

Industrial hemp, a farm crop with many uses, has been a no-no since 1970, but the 2014 Farm Bill allowed states to experiment with hemp pilot projects.

Hemp could be legal as a crop if a Senate and House conference committee agrees to include legalization in the 2018 Farm Bill. Legalization is in the Senate bill, but not the House version.

Senate Majority Leader Mitch McConnell, R-Ky., favors legalization. He is on the conference committee. There are objections from some House members. This could come up during the post-election lame duck session of Congress. Otherwise, it moves to the agenda of the new Congress.

Rep. Collin Peterson and Sen. Tina Smith, both D-Minn., believe compromise can be achieved during the lame duck session. After approval by Congress, the bill would go to President Donald Trump for his signature.

Legalization would please birds and people here who feed them. Hemp is an excellent bird food, nutritious, high in protein and fat. It has a long history as a popular addition to bird menus. It goes as far back as the feeders filled by George Washington (yes, that one).

In 1970 Congress declared both industrial and recreational forms of hemp illegal, even though the former has minuscule amounts of the chemical that powers the latter.

Congress outlawed both because it feared law enforcement could not tell one from the other. (Well, maybe if you rolled cigarettes of each.)

The ag bill would take industrial hemp out of the pokey. When that happens the Minnesota bird-feeding industry will be ready. In a bottom-line test recently completed, Minnesota birds liked the seed.

Carrol Henderson, recently retired as nongame superintendent for the Minnesota Department of Natural Resources (DNR), suggested a study.

He enlisted cooperation of the DNR, the Minnesota Department of Agriculture (MDA), the Minnesota Ornithologists' Union (MOU, aka state bird club), and All Seasons Wild Bird Stores. The MOU and All Seasons funded the study.

Managing the study was an ornithologist who specializes in bird preferences for food, David Horn of Millikin University in Decatur, Ill.

All Seasons provided feeders and the hemp seed, which it got from the MDA. Volunteers to offer hemp to birds were recruited.

Feeders containing hemp, black oil sunflower seeds, and white proso millet were used side-to-side: bird's choice. Thirty timed observations noting the bird preferences were made at a dozen homes and three nature centers.

Results of the study are to be released soon. Henderson told me that 10 to 12 bird species took the seed.

In his own informal study, Henderson offered hemp to birds visiting his Blaine yard. He found the seed "readily accepted by chickadees, nuthatches and cardinals."

Bob Dunlap, president of the MOU, told me that "overall, hemp seemed to be preferred less than black oil sunflower but on par with white proso millet."

Good news: Dunlap added that neither house sparrows nor squirrels showed much interest in hemp.

Margaret Wiatrowski, coordinator for the MDA's industrial hemp program, is helping farmers find markets for the plant. Seed used for bird feeding will broaden that market, she said.

This was the third year the experimental crop has been grown here, she told me. Forty-three licensed growers harvested 710 acres.

She said Henderson contacted her office about hemp as bird food and suggested the study.

Henderson told me that no other state is looking at hemp as bird food. "This gives our farmers a leg up," he said.

If approved in Washington, hemp as a commercial product also would need approval from the Association of American Feed Control Officials. That should not be an issue. Hemp as bird food is widely sold in Canada.

Read Jim Williams' birding blog at startribune.com/wingnut.