quarta-feira, 29 de junho de 2016


PART II: CHANGES IN BIOLOGICAL CLOCKS by Haidi D. Fiedler*, Faruk Nome* and Fredric M. Menger** *Department of Chemistry, National Institute of Catalysis, Federal University of Santa Catarina, Florianópolis, SC, Brazil.
**Emory University, USA.

In nature it is not possible to control all the variables. Conditions change with time, and warblers in Germany feel the difference. The natural sky has different appearances at different seasons, and the birds are particular about the sky they observe. When warblers are ready for spring migration they need to see a spring sky, and when they are ready for autumn migration there must be an autumn sky or otherwise they are confused.

A.J. Kirby’s photograph of Ponta das Canas/Florianópolis-SC - Brazil

Besides, the birds are able to notice different latitudes and longitudes, i.e. they navigate. The skies at different latitudes differ by the height of the North Star; it is in the zenith when we are at the North Pole, and at the north horizon when we are in the equator.

There has been much speculations on the sense of time and direction of birds….their special inner clock. How the clock works is not known but it must, of course, depend on physical and/or chemical processes within the organisms. Proposals suggest that the direction a migrating bird takes is decided by the coding of their genes.

Blackcap warblers are rather small songbirds that breed in Germany. Years ago, most of the blackcap warblers went to Spain and Portugal during the winter. But in the last 50 years blackcap warblers started traveling to Britain in the winter. Why are the blackcap warblers changing their winter vacation location?

Researchers from Germany and the UK believe that the shorter winter in Britain makes the difference! The “British” birds return about 10 days earlier to their summer breeding grounds in Germany. This short head-start of the British migrants allows them to claim the best territories and breed sooner. Females paired with the blackcap warblers that had traveled to Britain laid more eggs and hatched more chicks than those mated to the blackcap warblers that had gone south to Spain and Portugal.

Each year, warblers with genes orienting them towards Britain pass on those genes to more chicks. And as a consequence the number of warblers travelling to Britain increases. In the real world, even simple (or complex) things like bird migration patterns are always changing. Nothing in Nature is constant including the direction of mankind.

Reference: T.72.BIOLOGICAL CLOCKS by Fredric M. Menger, Emory University, USA

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