Life at a different pace: Annual itineraries are conserved in seasonal songbirds.
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Date
2014-06
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Abstract
The duration of life history state (LHS) reflects the adaptive strategy a species has evolved to cope with a changing
environment. Inhabitants at different latitudes may thus have significant differences in the rates of metabolic and
physiological processes underlying LHSs. Birds, in order to maximize their fitness in the environment in which they
live, seasonally switch from one LHS to another during the year. The present study investigated whether an annual
itinerary of a species would determine its rate of reaction to inductive long days. We compared the photoinduced
cycles of changes in body mass and testes, as indices of migratory and reproductive LHSs, between two long day
breeding species, the migratory redheaded bunting and non-migratory Indian weaverbird. Changes in body mass and
testis size were measured in photosensitive buntings and weaverbirds (n = 7 each) on short days (LD 8:16) subjected
first to 0.5 h weekly light increments until the light period was 13 h per day, and then maintained on LD 13:11 for
another 32 weeks. A similar observation was recorded on a group of buntings (n = 14) and weaverbirds (n = 9)
maintained on increasing natural day lengths (NDL; Lucknow, 26°55' N, 80°59' E) for 47 weeks. As predicted, the
rates of induction of seasonal cycles under an identical inductive photoperiod were significantly faster in temperate
buntings with five annual LHSs than in the subtropical weaverbirds with three annual LHSs. This suggests that annual
itineraries of songbirds with which they may have evolved with at their breeding latitudes, determine their response to
the external photoperiodic environment.
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Keywords
Body mass, bunting, life history state, testes, weaverbird
Citation
Malik S, Singh S, Rani S, Kumar V. Life at a different pace: Annual itineraries are conserved in seasonal songbirds. Journal of Biosciences. 2014 Jun; 39 (3): 485-491.