Lemming Influence Come South

     Lemmings are mouse-like critters, but a bit larger, that live on the Arctic tundra and have a four year life cycle of abundance and scarcity.  Tundra-dwelling snowy owls prey heavily on lemmings, including to feed their owlets during the short Arctic summers.  And, about every four years, some snowy owls, especially birds that hatched the past spring, drift south through Canada during October and November to winter in the northern United States where they hunt mice, rats and other prey.  Why every four years?  Because lemming populations peak about every four years and the zenith of that rodent's population, and the crash in lemming numbers soon after that climax drives snowy owl invasions south. 
     There was a big irruption of snowies into the northern United States during the winter of 2013-2014.  That winter there were 7 snowy owls in Delaware, including along Delaware Bay, 4 in Maryland, 14 in New Jersey, including in salt marshes along the coast and a whopping 35 snowies in Pennsylvania, for example.  And now in 2017-2018, so far, many snowy owls are in the northcentral part of the United States, including in Ohio, Indiana and the Great Lakes area.         
     When male snowy owls court their life-long mates each spring, they offer their partners gifts of lemmings to eat as part of their courtships.  The more lemmings male snowies give their mates, the more eggs those females will lay, up to eight or nine in each clutch, instead of the usual three or four per brood.  But, if lemmings are scarce, male snowy owls consume all the lemmings they catch and offer no presents to their mates.  Female snowies lay no eggs that year, which is good because there would be few lemmings to feed young owls that summer.  But as the lemming population builds on the tundra each year, so do snowy owl numbers.  Then lemming numbers crash, with few of the rodents being caught by snowies.  Then many of the young owls drift south for the winter to hunt prey, and we say an irruption of snowy owls is occurring.  
     During the winter of 2013-2014, three or four snowy owls were in the wide open, harvested-to-the-ground cropland around New Holland, Pennsylvania.  I suspect that open country, with few trees and fewer hedgerows, reminded the owls of the tundra where they were born. 
     We could see them sitting majestically on top of the snow cover in the cold, windy fields, usually fairly close to the rural roads where good looks at the owls could be had through binoculars and scopes.  Most of the time, each owl would just sit there staring back with squinted, yellow eyes at the gathering of people watching them.  One snowy owl, however, was feeding on a dead snow goose near a road.  I don't know if the owl killed the goose itself, or if it was scavenging the dead body.  Two things for certain, however, many noisy snow geese had been in those fields the day before.  And snowy owls are capable of killing snow geese.       
     It is estimated that there are about 30,000 snowy owls on the tundras of North America and Eurasia.  They do have an interesting life history, particularly with their irruptions south for the winter about every four years.  And they are magnificent birds; the biggest owls in North America.