2-23 Last Friday the temp spiked briefly up to 58 degrees F. on my thermometer. Those few hours of warmth changed a bird feeder dynamic which had held since Oct.

All winter two Yellow-bellied Sapsuckers had frequented my suet feeders: one juvenile and one adult female. And the juvenile always dominated, driving the adult away from the feeders. The adult only fed if and when the juvenile was either sated or absent. (Perhaps a mother deferring to her young?)

Since last Friday I have seen both sapsuckers foraging on apple and soft maple trees, but not at my feeders. And, this morning, with the temp. at 1 degree above zero I watched the adult female drive the juvenile away from the vicinity of the feeders. Every time the juvenile flew toward a suet feeder and tried to land, the adult dove into its flight path and herded it away.

Apparently the adult female now claims the feeders as part of her nesting territory. And apparently last Friday's warmth triggered that territoriality in her.

The newly dominant adult female will - along with her as yet absent mate - spend many weeks chiseling out a nest cavity in which she will lay her eggs this April.

Establishing a territory is the first step toward the great spring reproductive pulse. For sapsuckers here in my yard that season started last Friday afternoon. I seldom see such tipping points so neatly delineated... although they probably are. Our powers of observation are not geared to such subtleties. John