Silly Question

I think that's a perfectly reasonable question........birds certainly get tired - think of exhausted homing pigeons or the occasional blown-off course seabirds that get washed up around the coast - But, they have evolved perfectly for flight and with that comes a higher metabolism and a higher red-blood cell count compared to us mere humans. This enables their muscles to be fed with oxygen much more quickly and efficiently and reduces the lactic acid build up which we feel when our muscles have been used for long periods.

This is one reason why smaller birds have to feed almost constanty when flying - think of hummingbirds, whose wings beat between 12 and 90 times a second, dependant on species. On the other hand, you have the albatross , who have been recorded flying 550 miles in a day at speeds of 50 mph. Their flight is wind-powered using their enormous wingspans to catch the wind, using it to power them along. In a single foraging flight they can cover an incredible 1800 to 9300 miles - greater than the diameter of the earth. One Laysan albatross flew more than 24,843 miles in flights across the North Pacific to find food for its chick in just 90 days - truly amazing but i'm sure it had a good rest when it got back to the nest!

No such thing as a silly question except the one you DON'T ask - because then you'll never know the answer.

Physiologically speaking, bird muscles can run out of 'fuel' just as ours can: many migrants build up their fat reserves in the days before beginning migration, and then burn it off in one enormous burst of activity. If a bird gets blown off course or somehow makes a navigation error and burns off its fat reserves before landfall, there's not much it can do except ditch in the sea.

Certainly migrants get 'tired' - anyone who's birdwatched very much along the east coast of England in the autumn will surely have come across exhausted birds that have just flogged across the North Sea, perhaps against a headwind, and plonked down onto the first bit of dry land they come across. That's why wierd things turn up in people's gardens. They may only stay in such unfamiliar habitat for a few hours before moving on inland, to find more appropriate habitat (be it a wetland, or woodland, or whatever) and a food supply. The phenomenon of birds seeking shelter on ships is also well known, even if those ships happen to heading in completely the wrong direction. It's not rare for a bird to reach land but for it to be so exhausted it can't even find food once its landed - they become moribund and either fall prey to a predator, or simply keel over.

Larger birds that spend most of their lives on the wing - albatrosses and vultures for example - use gliding techniques to save energy. Small birds have to flap all the time but on migration may well fly at much greater heights than 'normal'. It's cooler up there and helps prevent overheating from prolonged muscular activity. And there is also a correlation between wing length and migratory behaviour in some closely related species. For example, whinchats migrate to Africa, but the similar-looking stonechats move much shorter distances often just within the UK. Side by side on the same twig they may look the same size and weight but whinchats have significantly longer wings because a longer, thinner wing is more efficient for flying a long way in a straight line.

Hope that helps!

Sorry, withdrawn, already answered.