Distance Champions: how birds fly thousands of miles without stopping
The image below shows tracked migration routes for shearwaters. A quick glance will show that the distances involved are quite impressive, covering thousands of miles. As it turns out, quite a number of birds undertake journeys that would make human pilots envious, and in some cases, these journeys are non-stop (i.e. without landing). The image below comes from here: (from here: http://www.encountersnorth.org/wildexplorer/birdmigration/Shaffer_fig1_Final.jpg
Before we look at how birds manage these distances, here are some records of note:Total Distance ChampionsArctic Tern:
Migration route of about 13,670 mi straight distance. They cover around 44,000 miles per year, however, as a result of long feeding voyages and a meandering migration path that differs greatly from the straight distance.Manx Shearwaters:
8,700 mi total migration distanceNon-stop Flight ChampionsBlackpoll Warbler:
2,000 miles; at least half of this is non-stop (over water), since they make it in 40-50 hours it is likely that the entire trip is done without landing. Not bad for an animal massing only 12-15 grams.Eastern Curlews:
4,000 miles non-stopBar-tailed godwit:
7,200+ miles non-stop. This is the current non-stop champion, and has been recorded with repeated telemetry series (see: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2664343/
). Note that these birds are continuous flappers, so they are not
soaring for this distance. They also cannot land/launch from open water, so there's no way for them to stop in route (confirmed with tracking).
They look like this: http://nzbirdsonline.org.nz/sites/all/files/1200670Bar-tailed%20Godwit%20male%20colour_D3S0626-1024web.jpgBurning the Engine
One of the primary factors involved in long distance migration is something that Colin Pennycuick has termed burning the engine
. Before migration, birds eat a lot of extra food and put on a huge amount of fat. As they fly, migrating birds burn the fat, which makes them lighter. This means they require less power to continue flying, so they do something quite interesting: they burn some of the muscle. That is, they burn the engine
. This provides more fuel while simultaneously keeping the birds at a high efficiency ratio of power available to cost of transport (it is more efficient to run a small engine hard than a large engine at partial capacity). This continues for the whole trip: some fat is burned, then some muscle, and repeat. The net effect is a 50% loss of body mass for godwits and others, along with an extraordinary long-distance journey.
For more on models of migration, check out Colin's 2003 paper on Burning the Engine