SNOWstorm

Fri, 02/23/2018 - 11:15am
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From  Elizabeth Dickens’ 1926 bird journal: “In Nov. and Dec. the greatest flight of Snow Owls ever recorded.” That entry goes on to identify sightings of 23 individual snowy owls on Block Island that winter.

Since 1926 there have been several irruptions of snowy owls into our region, and well beyond. An irruption is the phenomenon of a surge of snowy owls moving south of their primarily arctic range during winter. The movement of snowy owls during the winter months is not well understood. In “normal” years snowies regularly move south into the Canadian provinces, however, some may remain near their breeding grounds on the arctic tundra, or even move north to hunt — in winter darkness — from arctic sea ice. The 2013-14 winter irruption of snowy owls on Block Island, with approximately seven to eight birds, was likely the biggest since 1926-27. This year’s snowy owl irruption is proving even bigger. So far, 12 individual snowy owls have been identified on the Island, and there are likely at least a few more.

After the 2013-14 irruption, many scientists collaborated to establish Project SNOWstorm, an effort to study and learn more about snowy owls, especially the ecology of their wintering habits and movement. This research is primarily accomplished by the use of radio transmitters. These light-weight transmitters are attached to healthy owls as a “back pack”. Since 2013, more than 50 owls have been outfitted with these transmitters, which collect GPS location data and relay the information by cellular networks. To learn more about Project SNOWstorm and to see maps of where the individual snowies have traveled, visit their website at Project SNOWstorm.org.

On Feb. 14, 2018, members of the Project SNOWstorm team put a transmitter on one of the Block Island snowy owls. This was the first Rhode Island bird in the study. Named “Manisses,” this robust, second-year female was captured by Chris Persico and Lauren Gilpatrick, who are experienced raptor specialists with Biodiversity Research Institute (BRI) based in Portland, Maine. BRI has been studying raptors and their migrations from a Block Island station since 2012.

The Project SNOWstorm website notes the following

“The transmitters are held in place with a kind of backpack harness, made of low-friction Teflon® tape, that is a design that’s been used for decades on many birds of prey, including large owls. Similar harnesses have been used with satellite transmitters on snowy owls, with no effect on the owls’ survival or breeding success. They certainly do not restrict their flight — many of the owls we’ve tracked have flown thousands of miles to and from the Arctic.”

It is exciting to know that since the days of Elizabeth Dickens, Block Island continues to be an important location for avian research. You can read about, and follow the progress of Manisses at https://www.projectsnowstorm.org/posts/logan-cape-manisses-island/

While the tale of Project SNOWstorm and Manisses is a ray of hope, the fate of many irrupting snowy owls is not always so positive. In fact, most birds — of any species — hatched in any given year do not survive one year (survival rates improve for birds after one year). Many irrupting snowy owls are hatched in the previous summer, and are considered immature birds. Research on irruptive years indicates that high food resources during breeding and fledging (leaving the nest) can result in a high percentage of young owls surviving long enough to leave the nest. But, for a species where three to eleven eggs may be laid, a good year may mean that 100 pairs of snowies could rear between 300 and 1,100 young who have to share and establish territories. This may be part of the cause for a snowy owl irruption into southern regions. However, it is likely that many of that fledgling class will not survive the first year, as they strive to find territory where they can feed themselves, migrate unfamilar routes, avoid predators and solid objects not usually found on the tundra, and fend off pathogens and poisons that they may encounter, in an environment that is very different from their normal arctic range.

In the winter of 2013-14, six of the known seven snowy owls did not survive the winter. A necropsy on one of those birds indicated an emaciated condition and “fungal infection” as the cause of death. Many of this winter’s snowy owls will also not survive to move back north. But we will all continue to be moved by their majestic presence and enjoy their winter company. Please give the birds a respectful distance when viewing, their existence is already stressful without having to be wary of potential threats to their peace. 

And, we will hope that “Manisses” is one who makes it to her second year of life, and will provide us a glimpse of her annual travels. 

Notes: Please contact Kim Gaffett if you discover a dead snowy owl. We hope to have several birds necropsied so that we can learn about their causes of death, and to get as complete a count as possible of this winter’s snowy owls on Block Island. In Elizabeth Dickens’ era, this owl was called snow owl.