REGION — According to the website www.project snowstorm.org, which is concerned with snowy owls, every few years, “for reasons that are not entirely understood,” a number of the raptors leave their winter ranges in southern Canada, and migrate down into the United States in an event known as an “irruption.”

The winter of 2013/2014 produced an irruption of historic proportions, and there were more snowy owls seen in states stretching from Vermont to Tennessee than have been seen in perhaps 50 years.

There were many sightings in the Upper Delaware Valley, including the one above, which was spotted in Damascus Township in early April. Residents in the area say this particular bird died, perhaps of starvation.

The folks at Project SNOWstorm say starvation is not that common among snowy owls that fly south; they are more likely to die from collisions, consuming rat poison or from electrocution.

Most accounts of this irruption say it is linked to a spike in the number of lemmings available as food for the owls last summer.

There were so many lemmings in the region that snowy owls used the bodies of dead lemmings to line their nests as is attested to by a photograph featured on the Project SNOWstorm website.

The abundance of food led to an unusually large number of chicks successfully hatching and fledging. Some biologists say this abundance of young owls lead to increased competition for food during the winter, but others say the cause of the irruption is not simple and involves other factors.

In either case, the owls are making their way back north, and if history is any guide, the Northeast U.S. is not likely to see so many snowy owls again for a very long time.