Earlier today, we looked at why leaves change color--or, more specifically, why some trees change to red and some to yellow. Now, we turn our attention to the skies.
So, birds fly south for the Winter. But how do they pull off a trip like that, while you and I (or, maybe, just I) have no idea which way is north outside our hometowns? Actually, nobody knows for certain. But Matt Soniak at mental_floss has summarized three of the theories. My favorite:
A particularly cool study showed that migratory birds also use "celestial navigation" to find their way around in the dark. Captive birds placed in a planetarium changed their directional orientation when the star pattern on the ceiling shifted and became confused when the images of stars were dimmed. The scientists conducting the experiment suggest that birds use the layout of constellations in the sky as a compass.
I just like to imagine the phone calls between the bird guys, and the owner of the planetarium, both before and after the experiment.
Previously:
Image courtesy Flickr user Corey Leopold, via CC
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Birds only fly south for the winter if they live in the Northern Hemisphere.
90% of migrations are at night. Think it's the stars? Or something related? I think they know which way is South
Bird mainly use celestial and magnetic cues, but also orient themselves using polarized light from the sun at dusk. They also use cues from imagery of the land. What dictates their orientation specifications really depends on if they are social migrants or solitary migrants.
And also...
http://radio.weblogs.com/0105910/2004/07/28.html
Science recently had an article on how butterflies navigate in the daytime. They use the sun's position in the sky, but adjust for the time of day using their circadian clocks in their antennae. The antenna based clocks were a bit of a surprise.
Why is it, that when ducks fly south for the winter, they fly in "V" formation, and one side of the "V" is always longer than the other?
Wait for it...
There are more ducks on that side.
The most elegant proof of birds using stars for navigation was done by Steve Emlen. Migratory birds were placed in a wide funnel, lined with blotter paper on the sides, with a grate over the top and an ink pad at the bottom. When a bird hops up attempting to fly (say) south, it leaves a little mark on the paper. Let them do that all night, and their preferred direction of travel is documented by the birds themselves. It's a simple matter (in a planetarium) to rotate the stars 90 degrees the next night and watch the response (which was, the birds hopped in the new direction).
Aw haw... man, why do I have to follow that? I'll tell that joke a half dozen times today, at least... but damn, I was all excited about commenting, and now I just feel like a party pooper.
Well, anyway: my favorite theory about bird migrations has to do with behavioural fields and morphic resonance, as discussed by Rupert Sheldrake in The Presence of the Past".