---

A new collaborative project involving a large incursion of barred owls has taken wing this winter. Why should people give a hoot?

Well, besides being an amazing species with distinctive calls, they are an indicator of just how safe and clean the environment is for humans, said Norman Smith, director of the Massachusetts Audubon Society's Blue Hills Trailside Museum in Milton. Smith is working on the project with MassWildife and Tuft University's Cummings School of Veterinary Medicine.

Owls and other birds of prey are at the top of the food chain, and if there are changes documented in those populations that are the result of environmental problems, it can be detected a lot faster than it could be at the bottom of the food chain, say in the mice owls eat, Smith explained. By then, the threat is even harder to eliminate or reverse.

He points to the decline of bald eagles that eventually was traced, in part, to the pesticide DDT. It was found that exposure to the once commonly used toxin would result in a thinning of the egg shells, making them so delicate that they would break when the parents sat on them to keep them warm. Other studies found that acute exposure to DDT could affect the human nervous system, liver and kidney. The toxin was banned in the United States in 1972.

The effort just launched on barred owls is meant to determine why, over the years, there has been a seasonal phenomenon in winter where large numbers of owls have been observed in different areas of Massachusetts. The goal is to find out more about these large incursions and why they happen, Smith said. Is it a shortage of food, or increased breeding? And how far are they moving around? What are their migration habits?

Injured birds are being brought to licensed wildlife rehabilitators who will bring them to be examined at the veterinary school's wildlife clinic in North Grafton. Necropsies will be performed on dead barred owls to determine their age, sex, cause of death and what general health they were likely in before death.

Smith said he himself currently has two dead owls as specimens, likely the victims of automobile mishaps.

The lab reported that it already had several specimens found this winter, but necropsies had not been conducted on those birds as yet. Information gathered as a result will be compiled in the spring to determine whether there are any trends detected.

It is the first time there has been a physical collection of the species which is part of the effort to understand more about the periodic eruptions of barred owls, Smith said.

Nocturnal creatures, "owls generally aren't seen much, so if people see them, then generally that means there are more," he said.

Smith has been studying owls for the past 35 years. He has tracked snowy owls for 26 years, and since around 2001 has been attaching satellite transmitters to some of the wild snowy owls that winter at Boston's Logan Airport. The idea is to identify their migration patterns and ecological requirements. The work is done in collaboration with the USGS Forest and Rangeland Ecosystem Center in Idaho, Boise State University and The Owl Institute in Montana.

Snowy owls are the largest found in Massachusetts. Like the barred, the snowy would appear in large numbers in certain years for unknown reasons. Through the study, Smith said, they found that more breeding occurs if it's a good year for lemmings - rodents normally found in the Arctic and a food source for the owls. When they winter in Massachusetts, owls dine on rats and meadow voles, a relative of the lemming.

Barred owls, which are about 17 to 20 inches in size with a wingspan of 36 to 43 inches, have varied habitats, but largely prefer woodlands where they nest in tree cavities or roost on high berths of broad trunks. The owl is typically gray-brown, streaked with white horizontal barring on the chest and vertical barring on the belly. It has brown eyes and a round head lacking ear tufts, and feasts on a variety of birds, small mammals and amphibians, reptiles and invertebrates.

The owl is known for its distinctive hoot described by the Cornell Lab of Ornithology as sounding like the refrain "who cooks for you, who cooks for you all." Like other owls, they will call during the day as well as at night. During courtship, which typically begins in February, the birds project a loud series of vocal duets that have been likened to the sound of maniacal laughter. Breeding generally occurs in March and August.

They can be found locally and have expanded westward in the last century. In fact, more aggressive ones have challenged the endangered spotted owl out West, with hybrids developing.

For an up close and personal look at a barred owl, the Blue Hills Trailside Museum has a live specimen as part of its education program.

There are also some programs planned at local wildlife sanctuaries where people can learn more about owls.

And then, Smith advises, just keep an eye out. "They can show up anywhere," perched on tall buildings, in local sanctuaries, around reservoirs and in forests, he said.

SUSAN LaHOUD can be reached at 508-236-0398 or at slahoud@thesunchronicle.com.