Meeting Abstract
53.8 Sunday, Jan. 5 15:15 Comparison of the resident and migratory races of White-crowned Sparrows: new clues for migration RAMENOFSKY, M*; CAMPION, A; DILLAMAN, R; KRAUSE, J S; NEMETH, Z; Univ. of California, Davis; Univ. of California, Davis; Univer. of North Carolina, Wilmington; Univ. of California, Davis; Univ. of California, Davis mramenofs@ucdavis.edu
Comparison of the life histories of migrant (Z.l. gambelii) and resident (Z.l. nuttalli) White-crowned Sparrows reveals both distinctions and similarities that help to characterize the physiological mechanisms and constraints associated with migration. Both races exhibit phenotypic flexibility throughout the annual cycle that matches seasonal and energetic demands. For migrants there are 6 life history stages but 3 for residents. Aligning the stages, it becomes apparent that breeding for the resident extends over 6 months with activation beginning as early as January. During this period, the migrant completes wintering stage, expresses prealternate molt, prepares and executes vernal migration followed by breeding that concludes about the same time as both races become refractory by mid-July. Post breeding events involve prolonged postnuptual molt and wintering stage for residents while migrants molt then prepare and execute autumn migration to return to the over-wintering grounds. GIven this, the most prominent distinctions between the races are prealternate molt for migrants, timing, duration and maximal values of the gonadal steroids with elevations for residents observed from February to June while migrants only show a peak in late May and early June during territory establishment and mate guarding. During migration, migrants show remarkable changes – hyperphagia, fattening, increases in flight muscle profile, fiber diameter and color that alters with incursion of lipid droplets within the myofibrils prior to departure. Focus on these distinctions helps to differentiate the two races, identifies the timing and progression of these processes, and furthers our understanding of the constraints migrants face.
