February 2009, Tillie Creek Campground, Kern River Valley, Kern County, California
There seemed to be more sapsuckers than usual in the Tillie Creek Campground this winter, with Red-breasted and Red-naped sapsuckers being about equal in number, and one surprise Yellow-bellied Sapsucker.
Early on I began sketching the extremely variable tertial patterns, in order to identify individual sapsuckers and take a measure of their numbers and where they ranged in the campground woodlands. The tertial patterns proved nearly as reliable as fingerprints, and I was quickly able to identify every individual encountered and map out their movements.
I learned that some individuals are prone to focusing their foraging on a few closely spaced sets of trees, whereas others tend "trap-lines" of sap trees spread over distances up to 200 yards. This is a much greater distance than I had long thought a sapsucker would fly to work sap trees on the wintering grounds, and it occurred to me that I wasn't observing as many sapsuckers as I had earlier thought, but just a few individuals visiting sap trees in far flung corners of the campground.
It also became apparent that sapsuckers are "claim jumpers": typically I observed the same individuals tending their particular trees, but occasionally I encountered different individuals pilfering another bird's sap wells. One blue oak hosted a regular Red-naped Sapsucker but had two different Red-breasted Sapsuckers that slipped in from time to time to sneak a sip. But if the "claim owner" returned and found a "claim jumper" at the wells, a furious, winding pursuit followed until the interloper fled.