Last week's persistent snow flurries, wind and cold haven't harmed migrating birds in Butler County. It may have delayed their travel plans and mating seasons, but the unseasonable cold hasn't caused them any lasting damage.

That was the assessment of Chris Kubiak, director of education with the Audubon Society of Western Pennsylvania.

In fact, right now, migrating birds are more affected by the length of the day than the temperature, he noted.

Kubiak said, “Long-distance migrating birds, like the broad- winged hawk, they breed in Pennsylvania and overwinter in the Amazon.”

“Their timing to return is not affected by the weather,” he said. “These are birds that can move a pretty decent distance in one fell swoop.

“Their migrations are triggered by changes in daylight,” he said.

Kubiak said it is the short-distance feathered migrants that overwinter in, say the southeast U.S., that are late arriving this year.

“Those birds have a little more sensitivity to these temperatures. It's cold enough to slow their movement north,” he said.

“The blue-headed vireo, they are a little bit later this year as is the blue-gray gnatcatcher,” he said.

Bird watchers can blame the jet stream for the lack of birds in the area so far this year, according to Julie Snow, professor of geography at Slippery Rock University, who teaches classes in meteorology and climate change.

“If you look at the jet stream, it has really deep waves which create a movement of air over the northern United States,” Snow said referring to the band of strong air currents encircling the Earth.

The jet stream is dipping down from its usual position.

“Right now, we are sitting in a trough. The air in Pennsylvania is coming from Greenland. It's very cold air,” she said.

As the weather warms, Snow said the jet stream will eventually move back north into Canada.

In the meantime, Kubiak said, “I have heard from several people that the bluebirds haven't bred yet. Some of the breeding cycles are being delayed by the cold.”

But bird fanciers needn't worry about the various species going hungry in the cold spring, he added.

He said it's doubtful birds are getting more than 20 percent of their food from bird feeders even in the depths of winter.

“Birds are not going to starve because they are not at the feeders right now,” Kubiak said.

“For a lot of the seed eaters, a lot of the natural food supply has decreased naturally from the summertime, but there is still some,” he said.

“And conversely despite the weather there is still insect activity,” he said.

“For example, you are seeing robins congregating on half-salted pavement where the worms are coming out,” he said.

But this is the time to spruce up the old birdhouse or think about setting out some new ones.

Don't expect to see the same birds returning year after year, Kubiak said.

“A lot of these birds do not have a very long life span in the wild, two to three years. And others, like robins will not come back to the same spot every year,” he said.

Still you should clean out the previous tenants' mess before a new bird moves in.

Remove old nests to prevent parasites and lice problems.

“If you are going to build a new birdhouse, use wood that has not been treated. You don't want anything that could be leaching out chemicals,” he said.

Kubiak recommends using untreated pine or cedar to build birdhouses.

Consider what kind of bird you want taking up residence when you cut the hole for an entrance because the bigger the hole, the bigger the bird tenant.

Placement of the birdhouse also determines the type of bird that will nest in it.

Kubiak said, “For example, some birds like more woods like black-capped chickadees and cavity-nesting birds like the white breasted nut hatch.”

“If you're interested in bird boxes, look to see the habitat. You can attract anything from owls to bluebirds,” he said.

- Locate bird feeders at different levelsTo avoid crowding and to attract the greatest variety of species, provide tablelike feeders for ground-feeding birds, hopper or tube feeders for shrub and treetop feeders, and suet feeders well off the ground for woodpeckers, nuthatches, and chickadees.- Offer a variety of seeds in separate feedersA diverse mix of seeds will attract the greatest variety of birds. To avoid waste, offer different seeds in different feeders.- Provide suet during cool weather onlySuet (beef fat) attracts insect-eating birds such as woodpeckers, wrens, chickadees, nuthatches, and titmice. Place the suet in special feeders or net onion bags at least five feet from the ground to keep it out of the reach of dogs. Do not put out suet during hot weather as it can turn rancid; also, dripping fat can damage natural waterproofing on bird feathers.- Mix peanut butter and corn mealPeanut butter is a good substitute for suet in the summer. Mix one part peanut butter with five parts corn meal and stuff the mixture into holes drilled in a hanging log or into the crevices of a large pinecone.- Provide fruit for berry-eating birdsFruit specialists such as robins, waxwings, bluebirds, and mockingbirds rarely eat birdseed. To attract these birds, soak raisins and currants in water overnight, then place them on a table feeder, or purchase blends with a dried fruit mixture.- Provide nectar for hummingbirdsMake a sugar solution of one part white sugar to four parts water. Boil briefly to sterilize and dissolve sugar crystals; no need to add red food coloring. Feeders must be washed every few days with very hot water and kept scrupulously clean to prevent the growth of mold.- Store seed in secure metal containersStore seed in metal garbage cans with secure lids to protect it from squirrels and mice. Keep the cans in a cool, dry location; avoid storing in the heat.- Discourage squirrels from consuming feeder foodsSquirrels are best excluded by placing feeders on a pole in an open area. Pole-mounted feeders should be about five feet off the ground and protected by a cone-shaped baffle (at least 17 inches diameter) or similar obstacle below the feeder.- Locate feeders to reduce window collisionsProtect birds from collisions by not placing feeders within three feet of windows, if possible.- Keep cats indoorsOutdoor cats are especially dangerous to birds in the spring when fledglings are on the ground.- Clean feeders and rake up spilled grain and hullsUneaten seed can become soggy and grow deadly mold. Empty and clean feeders twice a year (spring and fall), or more often if feeders are used during humid summers.<em>From the Audubon Society</em>