Loggerhead Shrike Lanius ludovicianus Copyright 2013 Linda Kervin
Northern Shrike Lanius borealis Courtesy US FWS, Dave Menke, PhotographerThe name songbird conjures up an image of a colorful singing warbler. But one family of songbirds, the shrikes, are fierce little predators. No bigger than a robin, shrikes mainly eat insects, especially grasshoppers and crickets, but they also prey on rodents, small birds, lizards, snakes and frogs.
Utah has 2 species of Shrike: the Loggerhead which resides here year round and the Northern which breeds in tundra and visits Utah in the winter. Shrikes prefer semi-open country that has some trees, shrubs or fenceposts where they perch to watch for prey and then swoop to kill with their thick hooked bill.
Turkey Vulture in flight Cathartes aura Courtesy Utah Division of Wildlife Resources Scott Root, Photographer Licensed under CCL
Turkey Vulture Kettle above Logan Cathartes aura Courtesy and Copyright Andrea Liberatore, Photographer
Turkey Vulture Kettle above Logan Cathartes aura Courtesy and Copyright Andrea Liberatore, Photographer
On certain days in the spring and fall, the sky above my neighborhood looks like a scene from Alfred Hitchcock’s ‘The Birds’. As many as 60 large black birds swarm the sky, circling above the rooftops. On the busiest of days, people will stop their cars in the middle of the road to gawk at the sight. Some give a visible shiver when told that the birds are turkey vultures. But we have nothing to fear from these birds – in fact they should be embraced for the absolutely vital role they play in our environment.
There are lots of myths surrounding vultures, which in turn creates a misunderstanding about them. So let’s set the record straight on a few things. Vultures circle for two main reasons, neither of which involves waiting for a sick or wounded animal to die. The first reason is to take advantage of rising columns of air, called thermals, which generally occur in the mornings as the sun warms the air closest to the earth. Vultures are soaring birds and flapping their 6-foot wingspans takes a lot of effort, so they rarely do it. In fact these birds can fly for hours without a single flap. Circling within a thermal helps them travel higher and farther on much less energy.
The second reason vultures circle is to hone in on a food source. Turkey vultures are one of the few birds that have a highly developed sense of smell. Working together with their excellent eyesight, the birds soar and circle to pin down the location of their next meal.
What links this melodious thrush of northern Utah forests
(Kevin Colver: Song Birds of Yellowstone)
with a hawk that soars over farms, range lands and prairies in western North America?
Both Swainson’s Thrush and Swainson’s Hawk are named after the 17th century self-taught British naturalist, William Swainson. He was a contemporary of John James Audubon. Like Audubon, Swainson was a passionate solo collector, taxidermist and skilled illustrator of birds. Unlike Audubon, Swainson’s single intensive field expedition took him far to the south, sailing to eastern Brazil. During his two year stay, he amassed a collection of 20,000 animal specimens, including 760 bird skins. Swainson ultimately named 20 species new to science. Although he never visited North America, he nonetheless co-authored an encyclopedic four volume treatise about North America’s fauna.
Swainson’s Hawk and Swainson’s Thrush share another similarity, this one biological. Both birds migrate long distances to escape winter’s cold and hunger. Swainson’s Thrush winters in balmy tropical forests of South America. Swainson’s Hawk soars farther, all the way to the arid Argentine pampas. There this large slender hawk dines mostly on big flying insects, particularly grasshoppers and even dragonflies. Swainson’s Hawks migrate in groups, often along regular corridors. Every September, Hawkwatch volunteers and hardy birders have reported hundreds of Swainson’s Hawks rocketing past the Wellsville Mountains of northern Utah, flying amid several thousand migrating raptors of all kinds.
Birds migrate to avoid the snow, cold and lean times of northern winters. Migration poses natural risks, of course. Hawkwatch ornithologists also suspect that widespread use of two deadly organophosphate insecticides on Argentine crops kills many insect-eating Swainson’s Hawks. The plow, pavement and subdivisions have also reduced this hawk’s historic northern range, especially in California. In addition, foolish people still shoot this relatively tame hawk, not caring that its diet of rodents and grasshoppers benefits our farmers and ranchers.
Professional disappointments drove the quarrelsome William Swainson south as well, to New Zealand, where he died in anonymity. His namesakes, Swainson’s Hawk and Swainson’s Thrush, live on to cross and recross the equator in pursuit of perpetual summer and the feast it provides.
This is Linda Kervin for Bridgerland Audubon Society.
Hi, this is Mark Larese-Casanova from the Utah Master Naturalist Program at Utah State University Extension.
Walking across the yard late at night, the crescent moon was casting little light. A dark, phantom shape soared past our heads. It was silent, not making a single noise. It could only be one thing out here in the night- an owl, drifting off into the darkness.
Even though they hunt at night, owls use their vision to find prey. Owl eyes are proportionately large compared to those of other birds, and also have large corneas and pupils to allow more light into the eye. The retina, where an image is formed at the back of the eye, is so large that an owl’s eye is shaped more like a rounded cone or tube rather than a ball. Because the back of an owl’s eye is wider than the front, owls cannot move their eyes within the socket like other animals. To make up for this, owls are able to turn their heads three-quarters of a full rotation!
To supplement its acute vision, owl’s ears are particularly well adapted for hearing prey. In fact, some owls hear so well that they can catch prey in complete darkness. The feathers of the facial disk- the round, flat areas around the eyes- help direct sound toward their large ear openings. In addition, an owl’s ear openings are set relatively far apart on its skull, and at different orientations on each side. One is high and more forward on the skull, and the other is lower and to the rear. This allows owls to locate noises, such as the rustling of a mouse, by triangulation with remarkable precision.
Excellent sight and hearing are helpful to owls, but very quiet feathers help them sneak up on prey. Relatively large wings covered with feathers that have a velvety soft upper surface and a serrated edge reduce noise during flight. Owls even have feathers on their legs to help keep quiet!
Most birds sleep soundly in their roosts at night. But, it’s not uncommon for us to see an owl gliding through the darkness in search of its prey. Just don’t expect to hear them…
For Wild About Utah, I’m Mark Larese-Casanova.
Credits:
Images: Courtesy US FWS images.fws.gov
Courtesy and Copyright Mike Fish
Courtesy and Copyright Lu Giddings
Courtesy Wikimedia & licensed through CCL
Text: Mark Larese-Casanova, Utah Master Naturalist Program at Utah State University Extension.
Additional Reading:
Berger, C. (2005). Owls. Mechanicsburg, PA: Stackpole Books.
Lynch, W. (2007). Owls of the United States and Canada. Baltimore, MD: Johns Hopkins University Press.
Owl Feathers and Flight. (2012). In The Owl Pages. Retrieved September 20, 2013, from https://www.owlpages.com/articles.php?section=owl+physiology&title=Feathers
Owl Eyes and Vision. (2012). In The Owl Pages. Retrieved September 20, 2013, from https://www.owlpages.com/articles.php?section=owl+physiology&title=Vision
Northern Shrike
