Wild Side: Short-eared owls

They haven’t been around since they failed to show up in Katama in the mid-’80s.

0
Short-eared owl in winter at Seedskadee NWR, Wyoming. — Via USFWS

I could never pick just one favorite bird. But surely on the short list would be the short-eared owl, a crow-size, brownish bird of tundra, rangeland, and grassland.
Once a well-established species in our region, short-ears disappeared as a breeding bird on Martha’s Vineyard around 1986, when a pair failed to show up for duty at Katama. The owls hung on as breeders on Nantucket and Tuckernuck into the past decade or so, taking advantage of large tracts of grassland preserved on both islands. As far as I can tell, there are no recent, confirmed reports of the species nesting in the Bay State, though spring migrants sometimes hang around suitable breeding habitat in a way that suggests possible nesting.
As a species, the short-eared owl is not at particular risk across its huge global range (much of the Northern Hemisphere and portions of the Southern, with about 10 recognized subspecies worldwide, including island-endemic populations in places are far-flung as Cuba, the Galapagos Islands, and the Falkland Islands). But in much of North America, the species is declining rapidly in numbers. These owls are listed as “endangered” in Massachusetts. NatureServe, an international conservation collaboration that tracks the status of wildlife, shows short-eared owls as “imperiled,” “critically imperiled,” or “possibly extirpated” throughout the Northeastern United States.
To be sure, it’s hard to reconstruct a definitive baseline picture of this owl’s abundance in New England. The species has no use for forests, and so before the onset of European-style settlement and agriculture, short-eared owls would have been limited mainly to settings like salt marshes for nesting in the region. With the wholesale deforestation of New England for farming during the 18th and 19th centuries, this was surely one bird that benefited from the changing habitat; short-ears don’t like to nest on actively grazed land, but as the sheep-grazing industry declined through the 19th century, abandoned grassland and pasture offered a wealth of good nesting habitat. The owl’s relative abundance into the early 20th century, in other words, was a historical aberration, a species of tundra and prairies temporarily finding a niche in a human-modified landscape.
One factor inimical to our short-ears has undoubtedly been increasing numbers of small mammalian predators, notably skunks and raccoons. Both, famously, were introduced or reintroduced onto the Vineyard within living memory, and even on the mainland, I expect these species have increased in numbers thanks to human resources, from crop fields to trash cans.
But the largest single factor driving the decline has surely been the loss and fragmentation of the expanses of grassland that short-eared owls prefer for foraging and require for nesting. The regional decline of this species is a good illustration of how wildlife populations work in a fragmented landscape. There may still be pockets of habitat large enough to support a pair of short-eared owls. But one isolated pair is not a sustainable population over the long run. As small, isolated populations blink out one by one, there are ever fewer individuals moving around to recolonize habitat where breeders have disappeared.
Despite their dismal regional status as a nesting species, short-eared owls continue to show up regularly here as migrants and wintering birds. Even among migrants, I believe a decline is evident: Reports of multiple birds, once frequent, have become scarce, and here on the Vineyard, confirmable reports of this species have dwindled to a small handful annually (and none at all, in some years). The picture is muddied a bit by the possibility of mistaking northern harriers or barn owls for this species at long range or in dim evening light. This decline presumably reflects trouble in the breeding populations to the north, in the Maritime Provinces and eastern Ontario, from which our migrants presumably originate.
Given a bit of experience with this species, it’s not hard to recognize. Perched on the ground, they resemble an upright clod of mud but show an owl’s large eyes and saucer-shaped face. Short-eared owls display the odd, floating, moth-like flight typical of owls generally, and even in dim light, a bird showing that flight pattern and foraging low over grassland in semidarkness (also occasionally during the day) is likely this species. Harriers are much more strongly diurnal, and show a characteristic white patch on the rump, while barn owls tend to perch-hunt rather than cruise steadily. All three predators share a preference for small mammals, such as mice and meadow voles, as prey.
I wish I could tell you a reliable time and place to see this remarkable bird. If you birded Katama, Long Point, or Quansoo carefully every evening at dusk from mid-November to mid-April, the nomadic winter period for this bird, you’d have good odds of seeing at least one short-ear. But any random expedition to find this species has slim odds of success. Conditions have changed dramatically for this elegant raptor, and it doesn’t look like the Bay State’s short-eared owls will be bouncing back.