Document Detail


Seasonality in a temperate zone bird can be entrained by near equatorial photoperiods.
MedLine Citation:
PMID:  17254997     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Birds use photoperiod to control the time of breeding and moult. However, it is unclear whether responses are dependent on absolute photoperiod, the direction and rate of change in photoperiod, or if photoperiod entrains a circannual clock. If starlings (Sturnus vulgaris) are kept on a constant photoperiod of 12h light:12h darkness per day (12L:12D), then they can show repeated cycles of gonadal maturation, regression and moult, which is evidence for a circannual clock. In this study, starlings kept on constant 11.5L:12.5D for 4 years or 12.5L:11.5D for 3 years showed no circannual cycles in gonadal maturation or moult. So, if there is a circannual clock, it is overridden by a modest deviation in photoperiod from 12L:12D. The responses to 11.5L:12.5D and 12.5L:11.5D were very different, the former perceived as a short photoperiod (birds were photosensitive for most of the time) and the latter as a long photoperiod (birds remained permanently photorefractory). Starlings were then kept on a schedule which ranged from 11.5L:12.5D in mid-winter to 12.5L:11.5D in mid-summer (simulating the annual cycle at 9 degrees N) for 3 years. These birds entrained precisely to calendar time and changes in testicular size and moult were similar to those of birds under a simulated cycle at 52 degrees N. These data show that birds are very sensitive to changes in photoperiod but that they do not simply respond to absolute photoperiod nor can they rely on a circannual clock. Instead, birds appear to respond to the shape of the annual change in photoperiod. This proximate control could operate from near equatorial latitudes and would account for similar seasonal timing in individuals of a species over a wide range of latitudes.
Authors:
Alistair Dawson
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Publication Detail:
Type:  Comparative Study; Journal Article    
Journal Detail:
Title:  Proceedings. Biological sciences / The Royal Society     Volume:  274     ISSN:  0962-8452     ISO Abbreviation:  Proc. Biol. Sci.     Publication Date:  2007 Mar 
Date Detail:
Created Date:  2007-01-26     Completed Date:  2007-03-15     Revised Date:  2013-06-06    
Medline Journal Info:
Nlm Unique ID:  101245157     Medline TA:  Proc Biol Sci     Country:  England    
Other Details:
Languages:  eng     Pagination:  721-5     Citation Subset:  IM    
Affiliation:
Centre for Ecology and Hydrology, Monks Wood, Huntingdon, Cambridge PE28 2LS, UK. asda@ceh.ac.uk
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MeSH Terms
Descriptor/Qualifier:
Acclimatization / physiology*
Animals
Geography
Gonads / anatomy & histology,  radiation effects
Molting / physiology*
Organ Size
Photoperiod*
Reproduction / physiology*
Seasons*
Starlings / physiology*
Comments/Corrections

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