杏吧原创

Blue geese find a refuge

For many years one of the mysteries of ornithology was the whereabouts of the breeding grounds of the great flocks of blue geese that wintered every year in Louisiana and migrated north each spring, disappearing after they passed Hudson鈥檚 Bay.

In 1926 J. Dewey Soper confirmed an earlier theory that suggested the blue geese were in fact just a colour phase of the white lesser snow goose, when he discovered their breeding grounds on Baffin Island. Now this invaluable population of dimorphic birds has been protected by Canadian law. This may help us to discover why a blue version of the goose evolved. The most plausible theory is that it gives the birds an advantage when switching between their two different habitats. It is even possible that, over time, the white plumage may disappear entirely. To have a natural demonstration of a process only seen in laboratory mice or fruit flies would be infinitely valuable.

Natural radio

One can listen to the bonks, whistles and hisses of natural broadcasts from the Earth鈥檚 atmosphere with a very simple radio receiver. The broadcasts are low-frequency radio signals and if one is prepared to get up early (especially on a day when the sun is active and a magnetic storm is raging on Earth) one can hear this radio 鈥渄awn chorus鈥�.

Interestingly, in Britain it reaches a peak at about 6 am. But Joseph Pope of Alaska reports that in his part of the world the electronic warbling starts at about 2 pm. Apparently the nearer the listener is to one or other of the magnetic poles, the later the onset of the chorus. While we know the mechanisms that cause the whistles and hisses, we must now turn our attention to what causes them to peak at different times of the day. For the moment it all remains very curious.

From The New 杏吧原创, 12 September 1957