MILFORD – The upper and lower parts of most birds’ bills shut neatly. Not so with crossbills.

Their curved mandibles cross over like two tiny scimitars. A birdwatcher needs to be quite close to see that the bills cross. The birds are the size of a sparrow.

Crossbills are found only in forests of trees with cones, such as spruce, larch, hemlock and pine. Usually crossbills are high in the tops of the trees, where the cones are.

Cone-bearing trees do not bear cones every year. One or two years may go by before a heavy cone crop appears over a vast area. That means crossbills must live as nomads, traveling far to find food. This year, the spruce trees are producing a bountiful crop of cones in the Bangor area.

This winter should be a good one for finding crossbills.

Recently several Audubon members took an excursion around the Sunkhaze National Wildlife Refuge in Milford to look for crossbills.

The paved road turned to dirt, and it took many stops to look and listen for birds. The birders found chickadees, nuthatches and kinglets in the spruces, larches and hemlocks.

At last, a greenish-yellow bird high in the top of a larch tree looked promising. It was a female red crossbill calling loudly from her high perch.

Her mate, a dull red with black wings and tail, was foraging among the cones below. He was moving among the branches as parrots do, grasping branches with his bill as well as with his feet.

The next stop featured a flock of more than 25 red crossbills. They flew in big circles several times and landed in a hemlock tree laden with tiny cones. They climbed around in the crown of the tree, using their bills as well as their feet to climb, and feeding on seeds in the cones.

They flew several more circles around and landed on several poplar trees, appearing to eat the buds. Then they landed on a huge dead pine trunk with no bark, climbing around on its branches, appearing to find food in cracks in the wood. The birders watched them for quite awhile, and marveled at their versatility in feeding, considering that cone seeds were their preferred diet.

A later foray onto Web sites of American Museum of Natural History and Birds of North America verified that crossbills do sometimes vary their diet in the way the birders observed.

The birdwatchers left the Sunkhaze happy to have seen the red crossbills close enough to observe their unusual bills, their strange way of climbing around in a tree, their way of eating cone seeds and ways they vary their diet.

For information on Fields Pond Audubon Center in Holden, call 989-2591.