Sorry for the hiatus. Since last I wrote I've moved house and been to New Orleans. Although The Big Easy didn't flood, tornadoes in the southern states meant a days delay to my return and a very very bumpy flight from New Orleans to Chicago. Not something that this week's animal of the week would experience -- by flying only in the best conditions, Anser indicus (bar-headed geese) are able to cross the Himalayas under their own steam, flying at heights of 10 km, in just 1 day.
These pretty, small geese are some of the highest flying birds, and scientists have long wondered how they could scale the Himalayas. The problem is not just the height of the mountains, but also the low density air making it harder to gain lift, with less output from each wingbeat. People had thought that the geese used tailwinds that whip up the Himalayas during the daytime to help them on their way, but a new piece of research published in Proceedings of the National Academy of Science USA shows that they mostly fly at night, mostly. By flying when the air is still, the the geese avoid potentially dangerous air currents that would blow them off course or even cause injury, allowing them a non-turbulent, predictable journey -- pretty important in this low oxygen environment where mistakes could cost a bird its life.
The geese breed on the plateaus of central Asia, but overwinter in India. Their trip across the Himalayas is one of the most remarkable migrations in the natural world. Not only have they evolved to fly at the right time, but other adaptations to flying through the low-oxygen, low density air at 33 000 feet include haemoglobin with high oxygen affinity and wings with a larger surface area than those of other geese of their weight.
For those of you wishing to know what happened in the AV vote for the frog, turn out was so low that no decision cold be reached...unfortunately the same didn't happen in real life.
