A hint of spring
Delivering hope to some of us that winter will one day end, four American Robins appeared to sip water from a bird bath near East Cascade Avenue Wednesday afternoon.
So are they migrating?
Martha Fischer, a bird educator with Cornell Lab of Ornithology in Ithaca, NY, answers some of life's persistent questions about Robins in a blog for school-aged kids at www.learner.org.
She says the birds know when to migrate by the length of daylight. At mid- to late-winter, birds begin to feel restless. They have an internal clock, and they know that soon it is time to start moving north.
Their restlessness (ornithologists call this pre-migratory restlessness "zugunruhe") becomes irresistable depending on the length of day...but birds won't start to migrate just any old time. They wait for the weather and temperature to be right, Fischer says.
Robins follow behind the spring thaw ...and they wait for favorable winds. They want a tail wind-for the south wind to come along and help them move north. So, knowing when to migrate involves an internal clock, a feel for temperature, and the right weather patterns that create south winds.
Some robins can fly 200 miles. Their average flight speed is 20-30 mph.
Migration is slow, and can take many days. Because they move north following the isotherm or spring thaw, movement is sporadic. They might go 200 miles one day, and then rest and feed for the next two days before moving another hundred miles.
Their migration can take two, three, even four weeks.
Whether they stay a day or a season, their arrival was a welcome sight.