Birder’s Notebook: Short-eared owl: Nomadic owls are here for the summer
Each spring from late April to mid-May, short-eared owls migrate into the region, often finding a stillsnowy landscape. They course over open habitats throughout the Seward Peninsula with buoyant, floppy, moth-like flight in search of their main food: voles and lemmings.
When small rodents are plentiful, many short-eared owls may stay to breed, and we are treated to a summer of owl sightings. In years when voles and lemmings are scarce, these nomadic owls continue on their way in search of more fruitful hunting grounds and the sight of an owl becomes rare.
This year we are in luck. It seems voles thrived under our winter layer of ice and emerged in large enough numbers to sustain owls. I’ve been seeing what seem to be breeding pairs on each of the three roads out of Nome.
Soon after arrival, the owls establish territories where prey is available. The male performs a “sky dance” over a territory to attract a mate. He spirals up in tight circles into the air, hoots and hovers on fanned wings and tail, then swoops down while clapping his wings together loudly beneath his body. Once a pair bond is established, the birds are believed to remain together only for one breeding season.
Short-eared owls nest on the ground. The female uses grass and body feathers to build a cup, often hiding it in tall, dried grass. Mottled tan and brown coloration camouflages her well, and an incubating female will stay motionless on the nest until an intruder is only a few feet away.
The female typically lays four to eight eggs at intervals of a day or more apart. Incubation begins at various times during egg laying, so the nestlings are different sizes. This gives the larger chicks an advantage if prey becomes scarce.
The female incubates for about a month and brood the nestlings while her mate brings her food. Several weeks after hatch, the owlets leave the nest on foot before they can fly. Both parents protect and feed the dispersing young.
Fledging occurs about 30 to 35 days after hatch, so the first young owls on the Seward Peninsula may be flying by the third week of July.
Short-eared owls hunt at any time of the day or night, but evening is a favored time. The owls fly buoyantly, low over the ground, with slow, powerful wing-beats in search of prey. Sometimes they scan from a perch. They often hover before dropping to make a kill.
Voles and lemmings are the owl’s main foods, but short-eared owls also dine on shrews, weasels, songbirds and shorebirds.
Short-eared owls use hearing more than vision to locate their prey. Their ear openings are asymmetrical, one being higher than the other, which allows the birds to triangulate to locate prey precisely.
The owl’s body mass is low compared to its large wing size, so they can fly slowly and have agility in the air with little wing noise during flight. This allows them to hear well in flight and to fly silently so prey can’t hear them coming.
Short-eared owls are in turn eaten by other raptors including snowy and great-horned owls. Jaegers and ravens plunder their nests, eating eggs and nestlings, and will prey on flightless young.
The owls aggressively defend their nesting territories from raptors, including other short-eared owls as well as jaegers and ravens.
I recently watched a typical defense in which an owl launched off the tundra, likely from a nest, flying powerfully and directly up to intercept a passing rough-legged hawk. The owl stopped short at the last second before contact, pulling up and presenting its talons to the hawk, which maneuvered evasively and continued on its way. The aerial charges continued until the hawk was no longer seen as a threat.
When engaged with other shorteared owls in either territorial defense or courtship, talon grappling may occur. The birds may tumble together, almost to the ground, before breaking away.
Worldwide, short-eared owls are one of the most widespread raptors. They are found throughout much of North America, breeding and wintering in open country such as marshes, grasslands and tundra.
In 2009, raptor researchers Jim Johnson and Travis Booms satellitetagged 14 short-eared owls along Nome’s road system to investigate their seasonal movements. The 14 owls left the Seward Peninsula on their southern migration between August 8 and September 25. September 3 was the average departure date.Ten of the owls followed the Central Flyway east of the Rocky Mountains, and four traveled west of the Rockies along the Pacific Flyway to scattered locations in the western United States. One owl traveled nearly 4,000 miles into Mexico before its transmitter failed. Only three of the transmitters remained active on live birds through the entire winter. Those owls wintered in central California, southern Idaho and northern Colorado. None of those three birds returned to Alaska the following spring.
It is not surprising that the owls do not return faithfully to the same breeding areas since they depend on prey that varies greatly in abundance and distribution from year to year.
Short-eared owls are listed as a Bird of Conservation Concern by the U.S. Fish and Wildlife Service. In North America, multiple studies indicate their numbers have declined by 70 percent in the past 50 years. While their habitat in Alaska is still intact, in the Lower 48, the disappearance of grassland habitats on which they depend is thought to be the driving cause of their unfortunate decline.