Behavioral and physiological traits of migrant and resident white-crowned sparrows: a common garden approach.
To accommodate a migratory life history, migrants express a greater number of physiological and behavioral stages per annum than residents and are thus considered to have higher finite state diversity (FSD). To investigate the physiological mechanisms and constraints associated with migration, direct comparison of two subspecies of white-crowned sparrow - migrant,Zonotrichia leucophrys gambelii, and resident,Z. l. nuttalli- were made under common garden conditions of photoperiod and housing, as birds progressed from winter through the vernal life history stages. We tested the hypothesis that migrants (higher FSD) respond differently than residents (lower FSD) to the initial predictive cue, photoperiod, to initiate and integrate the progression of vernal stages of prenuptial molt, migration and development of breeding. If differences in vernal phenology were noted, then the basis for the distinctions was considered genetic. Results indicate that (1) residents had a lower threshold to vernal photoperiod with elevations of plasma androgen, growth and development of reproductive structures preceding those of migrants; (2) only migrants displayed prenuptial molt, preparations for migration and migratory restlessness; and (3) neither baseline nor stress-induced plasma corticosterone differed across subspecies, suggesting energetic demands of the common garden were insufficient to induce a differential adrenocortical response in either subspecies, highlighting the impact of environmental conditions on corticosterone secretion. Thus, in a common garden experiment,Z. l. gambeliiresponds differently to the initial predictive cue, photoperiod, to initiate and execute the vernal stages of molt, migration and development of breeding in comparison to the shared stage of breeding withZ. l. nuttalli, confirming a genetic basis for the subspecies differences.
Department of Neurobiology Physiology Behavior, University of California, Davis, Davis, CA 95616, USA mramenofs@ucdavis.edu.
Marilyn
0000-0002-3694-8464
M
Ramenofsky
Department of Neurobiology Physiology Behavior, University of California, Davis, Davis, CA 95616, USA.|David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90095, USA.
Andrew W
AW
Campion
Department of Neurobiology Physiology Behavior, University of California, Davis, Davis, CA 95616, USA.
Jonathan H
JH
Pérez
Department of Neurobiology Physiology Behavior, University of California, Davis, Davis, CA 95616, USA.
Jesse S
JS
Krause
Department of Neurobiology Physiology Behavior, University of California, Davis, Davis, CA 95616, USA.|MTA-DE 'Lendület' Behavioral Ecology Research Group, Department of Evolutionary Zoology, University of Debrecen, Egyetem tér 1., Debrecen 4032, Hungary.
Zoltán
Z
Németh
D025041:Animal Migration; D000818:Animals; D003345:Corticosterone / Q000097:blood; D008297:Male; D018978:Molting; D017440:Photoperiod; D012098:Reproduction; D012621:Seasons; D046370:Sparrows / Q000097:blood / Q000502:physiology*
D003345:Corticosterone
Androgens; Corticosterone; Finite state diversity; Flight muscle hypertrophy; Migratory restlessness; Prenuptial molt