Whether you call them helicopters, whirleygiggers, pinwheels, gyros, spinners or some Yosemite Sam curse word it wouldn't be spring in Medford without them. Maple trees around the city are sharing their seeds with you and your neighbors. Remember to clean your gutters & downspouts to make sure they don't get clogged and you end up with a water problem.
From Wikipedia's Maple Tree article: http://en.wikipedia.org/wiki/Maple
The distinctive fruit are called samaras or "maple keys". These seeds occur in distinctive pairs each containing one seed enclosed in a "nutlet" attached to a flattened wing of fibrous, papery tissue. They are shaped to spin as they fall and to carry the seeds a considerable distance on the wind. Children often call them "helicopters" due to the way that they spin as they fall. Seed maturation is usually in a few weeks to six months after flowering, with seed dispersal shortly after maturity. However, one tree can release hundreds of the seeds at a time. Depending on the species, the seeds can be small and green to yellow and big with thicker seed pods. The green seeds are released in pairs, sometimes with the stems still connected. The yellow seeds are released individually and almost always without the stems. Most species require stratification in order to germinate, and some seeds can remain dormant in the soil for several years before germinating.
Hope you are having a great spring, be careful on the ladder & when potentially working around electric lines :)