Current Nature: Nantucket's Owls - A Little Hoot Goes A Long Way
Libby Buck •
Owls have been capturing people’s curiosity for centuries. Their mysterious lifestyle, haunting calls, and captivating round faces with large eyes are hard to dismiss. Most owls are nocturnal, hunting at night. Owls have many adaptations that aid with nighttime hunting. They have special combs on their feathers that help silence their flight allowing them to sneak up on their prey. Their eyes are large to support seeing in low light or darkness. The forward placement of the eyes on owls, like us, allows them to hunt and determine depth perception and distance from their prey. However, owls cannot move their eyeballs as we can; that’s why they have extra vertebrate bones to rotate their head 270 degrees. This rotation and the asymmetrical placement of their ears on their heads also helps them triangulate the sounds of their prey.
The owl species found on Nantucket are Barn, Northern Saw-whet, Long-eared, Short-eared, and Snowy. If you’re lucky enough, this is the perfect time of year to spot or hear one. An excellent opportunity to go owling is a calm, clear night with no wind. Since owls are so secretive, their call is one of the best ways to identify them. Barn owls have a very distinct loud screech you would think was from a scary movie, Northern saw-whets have a repetitive “toot” call, and Long-eareds make a series of “whoos”. Short-eared owls and Snowy owls are typically found by sight. Short-eared owls will come out at dusk and hunt over open grassland fields. Snowy owls will not make any sounds and usually rest during the day on the beach or in an open area during the winter months before returning to their arctic breeding grounds. People are always surprised to hear that Great Horned and Eastern Screech owls do not live on our island. There are many of both species on Cape Cod and Martha’s Vineyard, but it would be a rare sighting for Nantucket, since those owls typically do not like to travel over the open ocean.
Sightings for owls, besides their secretive nature, seem to be dwindling depending on the species. The main threats to owls are habitat loss and competition, food shortage, and human impact. In particular, Short-eared owls are heavily affected by habitat loss and competition. They depend on sandplain grassland habitats for hunting and breeding, which are disappearing at a rapid rate.
In 2023, Snowy owl sightings have been close to zero. Their population depends on their food source of lemmings at their arctic breeding grounds and usually follows a four-year boom and bust cycle. This year was a low lemming year, so there wasn’t enough food to feed all the new offspring. If you see a Snowy owl on the beach this winter, that would be big news, like winning the lottery. Since 2013, Project SNOWstorm has contributed to many Snowy owl population studies by attaching GPS transmitters on them. They have excellent, up-to-date information on Snowy owl movements.
The Barn Owl population on Nantucket has been studied over the years by researchers at the Maria Mitchell Association, and has been documented to be expanding but still faces many threats. Nantucket is located at the northernmost limit of their range, meaning any further north, the owls will not survive the cold temperatures. If we have a freezing winter on Nantucket, many first-year birds usually won’t survive because they don’t know how to keep warm or find food in frigid temperatures.
Most of these owl species’ diet is made up of small rodents such as mice, rats, and voles. This year, many owls have been found dead on the island due to secondary rodenticide poisoning. Winter is when humans tend to find unwanted visitors of mice and other rodents entering our homes, and we try to fix the problem by using anticoagulant-rodenticides. These anticoagulant-rodenticides, don’t instantly kill the rodent, but rather leaves them enough time to run away in a debilitated state. Owls and other predators see this as a chance for an easy meal, but unfortunately fall victim to a slow, painful death from consuming poisoned rodents. The anticoagulant prevents the animal’s blood from clotting, causing loss of mobility, liver failure, and drawn-out death. There is only a short window of time when an owl can be saved from this poisoning.
On Nantucket, we have seen an increasing number of owls, especially Barn owls, with this cause of death. This winter there have been five attempted rescues by LLNF staff, Offshore Animal Hospital, and Marine Mammal Alliance Nantucket, and only one Barn owl survived, thanks to the quick response of the Marine Mammal Alliance and Cape Wildlife Center. The easiest way to help prevent unnecessary owl death is to stop using anticoagulant-rodenticides and consider alternative methods of rodent control. Spread the word to your friends, neighbors, and the community: not only will you be helping the owls, but also many other animal species that prey on rodents.
Hopefully, your next owl encounter will be happy one, but if you come across an owl that seems to be in distress, you can contact the Marine Mammal Alliance, Offshore Animal Hospital, or Cape Wildlife Center for assistance. Check the weather for the perfect night and remember to be patient and quiet when searching for owls; I’m sure you too can have an unforgettable owl experience.
Stay tuned for more editions of Current Nature, a bi-weekly column featuring seasonal topics, natural history information, and advice on the outdoors from the staff at the Linda Loring Nature Foundation.