Creature Feature: Avian Irruptions

When winter arrives, avian guests do, too. Northern birds rarely seen here are sometimes forced into our area during this season. In 2013, arctic-dwelling snowy owls began flying around the shores of the Chesapeake Bay. A few were spotted at Sandy Point State Park and one caused a traffic jam as it landed on the signs hanging overhead on the Bay Bridge. 

Several of these owls were also seen along Maryland’s Atlantic shore and reported along the coastline all the way to the Bahamas. After winter, they flew back to colder climes. Since then a few have returned on occasion but nowhere near the numbers of that 2013-14 winter. This unusual invasion of snowy owls is called an irruption, a distinct shift in a bird species’ typical winter range.

The reasons for these irruptions vary. In 2014, the Great Lakes froze over and two diving bird species, the red-necked grebe and the red-throated loon, could no longer feed there. So they flew south to Maryland, where they are now fairly common.

Other smaller birds such as finches are displaced because of seed production and tree health. Ornithologist Ron Pittaway studies the health of trees and coverage plants in the Algonquin Provincial Park in order to predict winter irruptions he calls his “Winter Finch Forecast,” according to the Cornell Lab of Ornithology.

Last year, evening grosbeaks and purple finches irrupted when certain pine trees produced fewer seeds. The winter of 2012-13 had an irruption of pine siskins and red-breasted nuthatches due to a poor growth season for birch and pine trees.

For years the assumption was that a crash in the lemming population caused snowy owl irruptions (lemmings are their favorite food). Now it is believed the reason was an over-population of lemmings and a very successful nesting season for the owls. With almost a doubling of offspring, the young moved south. Along the Atlantic coast, the owls became skilled nighttime sea duck hunters. 

Setting up a bird feeder with a variety of seed and dried fruit will attract a variety of birds and give you the best chance of seeing one of these rare visitors in your yard. 

To see more rare birds, download the BirdsEye app from Cornell Ornithology or sign up on the MDBirding website