Why do birds sing in Spring?

Up here in the northern hemisphere spring has just started, bringing with it daffodils, sunlight and singing birds. But why do birds sing? They don’t have calendars like we humans do, so how do they know it’s time to start breeding? After all, it can’t be the weather, because where I live it’s been snowing today, but that hasn’t stopped the birds singing.

Scientists from Britain and Japan teamed up to solve this age-old problem. The result – birds sing not because of temperature changes or weather, but because of the lengthening days. As the days get longer, hormones are released which trigger the activation of a specific gene.

This gene gives the birds the urge to attract a mate and produce offspring – and just as humans gel their hair or wear make-up to attract a companion, birds are attracted to each other by singing. I suppose humans could sing to attract a mate, but somehow I don’t think it would be too likely to work. Just as giving a blackbird makeup probably wouldn’t inspire another blackbird to want to mate with it. But you never know…

Anyway, as always the big question is how on Earth did the scientists work out which gene was responsible? How did they know it was because of day lengths? Basically, they put a ‘genome chip’ in a sample of birds (Japanese Quails) to work out if any genes were activated or deactivated as the birds received varying amounts of sunlight each day.

They found that certain genes on the surface of the birds’ brains were switched on when the days were longer, and the cells with these genes then produced hormones that had already been known to give the birds the urge to mate. The result: birdsong, followed not too long afterward by baby birds.

It’s amazing to think how simple yet complicated nature can be sometimes. Interestingly, it is thought that humans may have genes affected by day lengths similar to those in the birds – these could be what causes some people to feel depressed in the winter.

Check out this great post on all things spring over on Exploratorium

Melting snow made water flow on Mars

In the search for life, Mars has been a bit of a let-down so far. A few decades ago everyone thought there were canals there built by little green men. It turned out that Mars’s surface features had just been misinterpreted. Then there was that famous rock half-way through the last decade that was thought to contain bacteria – it was actually a weird-shaped mineral. Then a few months ago we were told water had been seen flowing on Mars… only to discover that it was dust, not water. Oops.

But now a new discovery has raised the possibility of life existing on Mars, even if it died out long ago. Scientists have concluded that several gullies created millions of years ago were almost certainly formed by flowing water. Where did the water come from? Probably from melting snow, which started to thaw as the Martian spring began.

Like any planet, the angle of Mars’s axis of rotation varies gradually over long periods of time. In fact, it may have reached as much as 45 degrees or more several million years ago, double its current angle of around 23 degrees. This would mean that it had more extreme seasons, which could have contributed to the thawing of the ice. Another intriguing possibility is that water somehow burst out from underground springs.

It’s all very well saying water was flowing millions of years ago, but how do we know? Basically, scientists saw that the gullies all tended to point in the same direction, which would tie in with the idea that the gullies were something to do with the Sun melting ice. The Sun would be at the same angle each spring, causing snow to melt in the same locations, carving out these gullies.

Does this latest discovery have any big implications for the hunt for life? It does raise the chances that there was once life on Mars, although it was already quite well known that Mars used to be a wetter planet. Nevertheless, every step forward in the search for life is important, and I’m hoping that this discovery will be able to pinpoint scientists to the locations where life was most likely to have existed.