ABSTRACT
In this chapter, the authors determine how well they have collectively dealt with Charlie Lyman's admonition about the need for a broadly comparative approach in attempting to arrive at generalizations about hibernation. They extend Lyman's admonition by recognizing that there are "multiple pathways to spring" in birds as well as mammals. Many birds breeding at middle or high latitudes reduce their thermoregulatory costs in winter by major migratory movements to warmer regions or by shorter vertical movements from montane situations to lowlands. Many birds maintain homeothermy in winter cold, despite the diurnal habits of the majority which both restrict opportunities for foraging in the reduced photoperiods characterizing this season and burden these animals with prolonged nocturnal fasts. Winter survival of birds cannot be understood without noting the important role that behavior plays in adjustment to cold.
