New insight into the light-dependent magnetic compass of birds

Date: June 6, 2016

Source: Goethe University Frankfurt

Birds have a light-dependent compass in their eyes. This compass gives them information about the direction of the Earth's magnetic field. Prof. Roswitha Wiltschko's research group at Goethe University Frankfurt, together with French colleagues, has elucidated how this compass works at the molecular level.

Birds have two sensory organs for orientation and navigation in the Earth's magnetic field: They use their beak to measure the strength of the magnetic field, while their eyes provide directional information. One type of cone photoreceptors in the birds' eyes is sensitive to UV light and also contains a form of the protein cryptochrome. Previous studies of the Frankfurt researchers suggested that most likely it is this protein that enables birds to detect the magnetic field.

A cyclic reaction involving one light-dependent and one light-independent step takes place in the cryptochrome. Two radical pairs are formed during this cycle, and their unpaired valence electrons react to magnetic fields. The Frankfurt group, working in collaboration with Pierre and Marie Curie University Paris, have now discovered which of these two radical pairs is crucial for navigation in the Earth's magnetic field.

In a behavioural study on robins, the birds were subjected to two experimental conditions:

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Light and sound used against Rome's birds

TIRED of bird droppings on the city's most famous monuments, local authorities in Rome are resorting to unusual measures to try and scare off a million starlings that migrate to the Eternal City every year.

Armed with loudspeakers and light projectors, workers dressed in white overalls and masks have been seen walking around at sunset along the tree-lined embankments of the Tiber River where starlings tend to congregate.

The loudspeakers blast out shrieks of alarm used by the starlings and the projectors are shone into the trees to scare off the birds.

"Their reaction is immediate," city hall said in a statement on Friday.

"The starlings abandon the area and get as far away as possible from the area, which they consider dangerous," it said, adding that the method "respects the environment and the birds and does not create a nuisance for residents".

The sound-and-light attacks last around an hour and are always carried out at dusk for three days in a row to ensure the desired effect.

Rome has the highest number of starlings in Italy - around a million are estimated to migrate there every autumn and winter.

http://www.theaustralian.com.au/news/breaking-news/light-and-sound-used-against-romes-birds/story-fn3dxix6-1226518643665