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Great Horned Owl

Mystery Snow Story: Great Horned Owl Preys on Black Guillemot

Plate-219,-Black-GuillemotLet me first say that the scenario I describe is conjecture, albeit conjecture based on the evidence posted yesterday. Today’s post may well tell you more about my train of thought when interpreting signs in the snow than the actual events that took place! The tracks were discovered and photographed by Sally Grassi of Camden, Maine, who saw a large bird (I thought that telling you this would be giving away too much!) devouring something while perched on the snow at night. The tracks that may appear to some as leading to and from the kill site are marks made by something that came out of the sky – they come from and lead to nowhere. I apologize if they were misleading. Given the myriad of ways this scene could be interpreted, the guesses made were strikingly on the mark. Kudos to Kathie Fiveash, who correctly guessed the prey species.

Plot: A bird of prey attacked another bird and proceeded to consume most of it.

Characters: As to the species of predator, the fact that this activity took place at night points to an owl, and the size of the bird eaten (deduced from the size of its remaining foot and bones) narrows the attacking bird down to most likely being a Barred Owl or a Great Horned Owl, both of which are found along the coast of Maine in the winter. (Snowy Owls are diurnal and therefore, even though there are individuals that have irrupted into New England this winter, the likelihood of it being a Snowy Owl is minimal.) Although we can’t know for sure which species of owl it was, chances are great that it was a Great Horned Owl, as they routinely eat large prey, and Barred Owls only occasionally feed on birds this size.

As to the identity of the prey — the geographic location, the time of year, the few remaining feathers and the color of the remnant (unwebbed) foot and leg appear to eliminate all but the Black Guillemot. Although totally black with white wing patches during the breeding season, this alcid (member of the family of birds that includes puffins, murres and auks) has a mostly grey/white plumage in the winter, and brilliant orange-red legs and feet year round. It can be found throughout the year along the coast of New England where it hunts for fish, crustaceans and invertebrates in shallow water near shore. (Thanks to Sally Grassi for Mystery Photos, to George Clark for confirming prey I.D. and J.J.Audubon for the Black Guillemot illustration.)

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Great Horned Owls Courting

1-22-15  great horned owl IMG_5973The intense hooting of Great Horned Owls begins in late December or early January, about a month before actual mating takes place. Males call during most seasons of the year, but the period when the males are hooting vigorously lasts for a month or six weeks. During the mating season the deep, rich tones of the males are occasionally interspersed with the higher and huskier notes of the females. The answering calls of the females are heard for only a week or two, toward the end of the six-week period.

Eventually, when a male and female approach each other, they do a sort of courtship “dance.” The male cocks his tail, swells his white bib (see photo), and with much bobbing and jerking utters a series of deep sonorous calls that elicit calling responses by the female. He cautiously approaches the female, continuing much tail-bobbing and posturing. The owls nod, bow, and spread their wings as well as shake their heads. Courting pairs have been observed engaging in high-pitched giggling, screaming, and bill-snapping. Mutual bill rubbing and preening also occurs. Copulation concludes the courtship ritual, with both owls hooting at a rate of 4 or 5 hoots per second throughout copulation, which lasts 4 – 7 seconds. (Photo: Great Horned Owl, in captivity)

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Snowshoe Hare Succumbs to Avian Predator

1-14-15 snowshoe hare kill site 076The drama that goes on in our woodlands is never-ending, and winter provides us with a window into life and death scenarios. One of the most sought-after prey animals in northern New England is the snowshoe hare. Bobcats, lynxes, coyotes, foxes and fishers are some of the mammalian predators of this lagomorph. In this particular case, however, the predator had wings (determined by wing imprints in the snow and lack of tracks). While great horned owls do prey on hares, there was a tell-tale sign that it was a hawk, not an owl, which produced this pile of fur and bones. If you look to the upper left of the photograph, and to the upper right, you will see lengthy curved lines of bird droppings, or sprays, that were left by the predator as it plucked its prey. Because it was ejected forcibly, and didn’t just drop down on the snow where the bird was situated, the scat leads one to the conclusion that it was a hawk, not an owl, which deposited it. A woodland accipiter capable of capturing a snowshoe hare after an extensive chase, which this was, is the northern goshawk. (Thanks to Nicole Cormen for photo op.)

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Great Horned Owls Thaw Cached Prey

1-13-14 great horned owl l MH_20091001_225056_4Great Horned Owls are one of the earliest species of birds to nest in the Northeast –some are already sitting on eggs. Female Great Horned Owls do the lion’s share of incubating the eggs, while the male hunts for and brings her food. While they do eat small rodents, which they swallow whole, the diet of Great Horned Owls also consists of rabbits, hares, opossums, squirrels and skunks, which must be torn into small pieces before being swallowed. Great Horned Owls often kill more than they can eat at one time, and cache the extra food for later consumption, when food is scarce. Needless to say, during winter months the cached prey freezes, and if the prey is large, its consumption is challenging for a bird with a bill that’s designed for shredding and tearing. To solve this dilemma, Great Horned Owls sit on their frozen prey until it thaws, and then proceed to tear it into bite-size pieces.

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Striped Skunk Predators

2-8-13 skunk prey-david putnam005 (2)At first glance, this looks like any other kill site, but if you look closely at the hairs, you’ll see that it was a striped skunk that was preyed upon – a rare find, for two reasons. One is that striped skunks spend most of the winter holed up and only amble out during warm spells (which we had recently). Their mating season is also about to begin. The second reason that this find is unusual is that skunks have very few predators, for obvious reasons. Great horned owls and occasionally a coyote, fox or bobcat will risk being sprayed. In this case, tracks were not evident by the time it was discovered. Initially the lack of anything other than hair suggested that the predator was a mammal which carried off the skunk (great horned owls usually eat at the kill site). However, it turns out that the absence of bones, etc. doesn’t actually rule out an owl. According to the Cornell Lab of Ornithology, occasionally when a great horned owl kills more prey than it can eat, it caches the remains for later use. When in need of food, the owl will incubate frozen prey until it thaws and can be eaten. (Discovery and photo by David Putnam.)