Tuesday, May 4, 2021

Saw whet owls: A shrew’s nightmare

Saw whet owls appear nearly as strange as their name sounds. At seven to nine inches long, weighing in at two to six ounces, with a stubby wingspan of sixteen to nineteen inches, saw whets are the smallest owl in the Adirondacks, though surprisingly not the smallest in the world, coming in at twice the weight of the insect eating elf owls of the Sonoran and Chihuahuan Deserts. As with other raptors, female saw whets are larger than males.

Saw whet owls suggest an old pair of rolled up, mud-stained socks that sprouted enormous eyes and short, thick, finely feathered legs with relatively large talons. They are unbelievably cute, but as with all owls, do not be fooled. They are stone killers. Saw whet owls live up to seven years in the wild, over twice that in captivity, and their fossils have been reported from the late Pleistocene in Tennessee, which could be up to 120,000 years ago, long before our ancestors left Africa.

saw whetStrictly nocturnal, the solitary saw whet spends its days motionless in dense thickets, as well as on low obscuring deciduous or coniferous branches, often at eye level, its roundish outline camouflaged by the vertical brown and off-white tawny barring of its breast feathers, the mottled grayish wings and its neckless oval head with brown and white streaks radiating out from its goggle like face, and the eyes framed on top with a thick whitish “Y” shaped band, like bottomless quarter eyeglass frames. Immature saw whets have tawny torsos and brownish heads. The saw whet bill and cere, the soft fleshy bare patch where the nostrils are located on the upper part of the bill, are blackish.

The saw whet survives by disappearing into its surroundings, sometimes wrapping a wing around its torso and closing its eyes. If a saw whet suspects it has been spotted, it will probably stay still. When you are preyed upon by larger owls at night, and larger raptors by day, flying in the open can be a dangerous activity. Pine martens, ermines and crows are predators of saw whet nests. The noisy scolding of song birds may indicate the presence of a saw whet owl roosting.

Like screech owls, saw whets perch on low branches, listen and watch before diving on mice, voles, moles, shrews, and chipmunks. Small birds such as chickadees, sparrows and kinglets may also be taken, as well as large insects and the occasional bat. Saw whets are well equipped for such hunting throughout the night. Periods of plenty are followed by periods of want and saw whets will cache excess prey in various sites, brooding frozen carcasses to thaw them when necessary.

Saw whets have long tubular eyes, evolved to see in low light, with bright yellow irises, framing pupils which expand to enormous diameter to help in night hunting. Their eyes are packed with motion detecting rods, and enough cones to pick up subtle color contrasts in foliage and on the forest floor. If something moves, saw whets will likely see it. If your eyes were as large proportionately as a saw whet’s, they would be the size of grapefruits. You can see the eyeball while looking through the saw whet’s ear openings.

Hearing is probably the saw whet’s most efficient tool in detecting prey. The ears are concealed in the facial disk behind the eyes, and, as with many other owls, they are staggered, one larger than the other, one higher than the other, such that sounds, left or right, up or down, strike one ear before landing on the other a micro-second later. The eyes are locked in the skull sockets in such a way the owl can not move them and must swivel its head on its fourteen neck vertebrae, twice the number humans have, to look in a different direction, which can therefore be used to synchronize the sounds reaching the owls ears. Once a sound hits both ears simultaneously, by definition, the owl is staring at the location the prey must be. Therefore, saw whet owls can catch their prey in the dark.

As with other owls, flight feathers of saw whets feature tiny comb like serrations on the lead edge, as well as soft fringes on the outer edge, which break up the sounds of flight, enabling silent flight, such that prey targets can not hear the owl approaching, just as the owl is not distracted by the sounds of his own flight, while triangulating the positions of moving prey.

Owls lack crops, which other birds use to store food for later consumption. At the same time, they have no teeth, so they cannot chew their food, and they cannot digest bone, feathers, or fur. Prey are usually swallowed whole or brought back to the nest to be dismembered by beak and talon, and then shared. 

The owl’s digestive system is composed of two parts: the smaller proventriculus produce enzymes, mucus, and acid, which begin the digestive process, while the next stop, the larger ventriculus or gizzard, separates the indigestible parts, forming a pellet, which is stored in the proventriculus before being regurgitated by the owl hours later. Saw whet owls produce about two pellets per day, and the owl cannot swallow prey again, until the pellet is ejected. 

Saw whets defend territories of about 250 acres, and breed in the Adirondacks from March through May. They have a variety of calls, with males attracting females by emitting their high pitched “toot-toot-toot” calls continuously for long stretches through the night, about one toot per second, sounding like a distant truck backing up. When alarmed, the saw whet gives the “skiew” call, which is likened to the sound of a saw being sharpened by a whet stone, hence the owls name. When delivering prey to the nest, the male emits a faster, more staccato “toot-toot” call, and the female responds with a “swEE” call. As with other owls, frightened or threatened saw whets snap their bills loudly and rapidly, a sharp penetrating defensive noise. 

Saw whets occur from Juneau and British Columbia in a wide sweep southeast, not quite touching Hudsons Bay through Nova Scotia, all the way down from the southwest east to northern Florida, with some migration by northern saw whets. There is a thin tongue of resident saw whets in the central Mexican Highlands. There are about 2 million saw whets, and while they are not yet threatened, it is believed that their numbers are in decline. Starvation tends to be the number one killer of wildlife, and saw whet numbers are tied to rodent numbers, which tend to increase and decline in four-year intervals. Rodent numbers, in turn, are tied to hard mast production in the fall. Everything in nature is connected.

Saw whets compete with squirrels and starlings for nest sites in natural tree hollows or holes drilled by flickers or pileated woodpeckers. They will also adapt readily to man-made nesting boxes. Saw whet courtship consists of the male flying in circles above the female, some shuffling and bobbing on the branch the female is on, and possibly the presentation of prey such as a mouse. Males may cache prey in various cavities to convince females that they have chosen the right mate.

Saw whet owl

Unlike many other owls, saw whets are apparently not monogamous, pairing up only for that nesting season, and not only may a successful male support more than one nest, an example of polygyny, but the female will abandon the nest when the chicks are only about eighteen days old, sometimes taking up with another male, and raising a second brood, an example of polyandry. 

Female saw whets incubate the five or six white eggs they typically lay over a two-day period, for about 28 days, and for the first two weeks after sequential hatching, Dad brings all the food to the nest, with Mom brooding the chicks, leaving only once or twice a night to cough up pellets and evacuate waste. The female is adept at keeping their nest relatively clean, a condition that goes downhill when Dad is forced to not only continue providing all the food, but the housekeeping, getting rid of pellets, prey fragments, suffers in the female’s absence. Older chicks will help feed younger once the female is gone and will begin fledging at 4 or 5 weeks. Young are cared for several weeks after fledging and are sexually mature by nine or ten months.

Saw whet owls have a media celebrity, the saw whet who managed to be stowed away in the Rockefeller Center Christmas tree, cut down in Oneonta, NY in 2020, and transported all the way down to Manhattan, only to be discovered by the crew setting up the tree next to the skating rink. The owl was rescued and brought to a rehab center, which released the owl back into the wild after a check up revealed it was none the worse for wear!

Bird banding is a critical activity which teaches us about health, longevity, and how far birds travel during migration. Banders measure weight, size of bill, wingspan, etc. Age can be estimated by using a black light to examine wear and tear on flight feathers. An astounding 81,000 saw whets have been banded over a ten-year period throughout their eastern range, and about three thousand birds have either been discovered dead or recaptured in mist nets during migration and reexamined, providing a great deal of valuable information. The bands contain coded information on where the bird was banded and when, and sometimes a phone number to call to report a dead bird. Birds teach us about the health of our environment, as they face many challenges and typically travel through many habitats. Locally, veterinarian Dr. Nina Schoch, conservationist Larry Masters, and volunteers, banded saw whets at John Browns Farm during early October migration in 2019. If you find a dead bird with a band, please notify US Fish and Wildlife at https://www.pwrc.usgs.gov/BBL/bblretrv/.

Photos from top: The two saw whets together by Joe Kostoss, Eye in the Park; lone saw whet in enclosure by Kevin MacKenzie, saw whet with girl, by Ashley Adams. All provided by Adirondack Wildlife Refuge and Rehab Center

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Steve Hall

Steve and Wendy Hall run the Adirondack Wildlife Refuge and Rehab Center in Wilmington. They've been rehabbing and releasing wild animals for over 45 years, specialize in predators, keep wolves as the cornerstone of their educational program, and have lived in the Adirondacks for the past 20 years. The Adirondack Wildlife Refuge became a non-profit about 10 years ago.

Visit www.AdirondackWildlife.org to learn more.


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One Response

  1. Phil Fitzpatrick says:

    Thank you 🙏

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