With this latest instalment about grassland birds from Nate we will hear about the Short-Eared Owl!
It’s about time we talk about one of the most charismatic and iconic groups of birds found all across the world, owls! This particular species of interest today can be found throughout all Canadian provinces and territories during the breeding season – the Short- Eared Owl. The Short-Eared Owl makes use of a wide variety of open habitats, including grasslands, old pastures, and occasionally breeds in agricultural fields. Preferred nesting sites include dense grasslands. Perhaps this post should have been kept for Halloween as Short-Eared Owls are sometimes called “ghosts of the grassland” or “ghosts of the open country” due to their flight pattern and pale colour.
These owls can be identified by their almost perfectly rounded head with light brown borders around its cream white face. Their bright yellow eyes are contrasted by black eye patches that fan to the side making this bird look like it put on some mascara and fake eyelashes that slipped to the side. Its breast is cream-coloured with light brown streaking which becomes a dark brown ‘collar’ closer to the head region. This dark brown colouration with caramel streaking continues to the rear portion of the animal and covers the wings. But where does its name come from? Well, if you look rather closely you may see two tiny protrusions from the top of its head similar, albeit much smaller, to those found on the Great Horned and Long- Eared Owls.
What about those ears?
I’ve got some shocking news for you all but the real ears on owls aren’t even visible! What you’re actually seeing is extensions of feathers we like to call ‘ear tufts’ and are scientifically named ‘flumicorns’, potentially the greatest name in anatomy history. There isn’t a definitive answer as to why they have these tufts but some theories include improved camouflage, looking extra spooky to scare off potential predators, or to impress a mate during courtship. The ears of an owl are essentially holes covered in feathers in a rather strategic fashion. Owls hunt primarily with their hearing so their head is modified to capture sound at an impressive rate. Owls have a facial disk profile which means their facial features seem caved in and surrounded by a ‘bowl’ of raised feathers, giving their face an appearance similar to that of a satellite dish. These feathers can then be adjusted to better direct sound to the ear holes depending in the direction of the sound. Their ears also have another adaptation that makes them superb listeners. They are offset, meaning one is higher up on the head than the other, which allows the owl to determine if sounds are coming from above or below. With these combinations of features, owls can precisely triangulate the location of prey, even under a layer of grass or snow.
Adults feed primarily on voles but will hunt for a mix of smaller mammals including pocket gophers, muskrats and bats; a true variety of prey from the ground, water and sky! They also feed on a range of smaller birds including gulls, songbirds and shorebirds. Short- Eared Owls are one of the few owl species that build their own nest, with the female excavating a bowl-shaped indent and lining the cavity with grass and feathers. The female will lay an average of four to seven eggs and will produce a second brood if eggs are eaten or destroyed. During the breeding season they are easily disturbed by humans and will abandon nests due to nearby human activity. If food availability is plentiful they may stick around in their wintering range to breed.
Short-Eared Owls are facing a decline in population size due mostly to a loss of suitable habitat. These birds require large open and continuous areas that haven’t been broken up by activities that cause habitat fragmentation (the division of one large area into smaller patches of land). These fragmentations are often attributed to grassland conversion to cropland, livestock grazing, recreation and urbanization. The presence of invasive plant species and grasslands being taken over by shrubs, further disturbs the habitat for these birds. Although mostly nesting in grassland thickets, tundra with vegetation and occasionally overgrown pastures, these owls can also be found in wetlands and sagebrush thickets during the non-breeding season provided the habitat is large and continuous with no fragmentation. Their wintering habitat is a bit more flexible with owls being found in woodlots and coastal marshes. If habitat fragmentation wasn’t enough, the drainage of wetlands in coastal regions have impacted wintering ranges of Short-Eared Owls. Although the availability of open areas is instrumental in this owl’s distribution, food availability also dictates whether they will remain in an area. Their population size tends to fluctuate with the population cycles of their prey which is common with most predatory species. The COSEWIC listing of Short-Eared Owls was changed from special concern to threatened as of May 2021 but still remains a species of special concern under SARA. They are classified as threatened under the Manitoba Endangered Species at Ecosystems Act. Habitat restoration projects have helped Short-Eared Owl populations by restoring and preserving suitable habitat free from fragmentation and invasive plant species.
Author: Nathan (Nature Nate) Entz