1Hi, it's Esther.
2I love watching birds.
3It's so amazing how they can soar through the air.
4Like this eagle.
5It's flying off the top of the Burj Khalifa.
6The tallest skyscraper in the world!
7And it's making it look so easy.
8In case you're wondering, the eagle didn't fly up there on its own.
9He was released by a trainer to promote the conservation of endangered birds.
10Pretty cool!
11Someone named Nova has a question about birds in flight.
12Let's give Nova a call now.
13Hi, Esther!
14Hi, Nova!
15I've got a question for you.
16How high can a bird fly?
17That's a great question!
18Birds fly for all sorts of reasons,
19but one of the main reasons is to hunt.
20See this hawk?
21It's looking for food.
22Though hawks like these can see amazingly well from up high,
23it's choosing to fly pretty close to the ground.
24That way, it can swoop down quickly and surprise the animals it wants to hunt.
25Though most birds like hawks are able to fly really high,
26it's pretty normal for them to fly low when they're hunting.
27And that makes sense.
28Their food is down there!
29But there are many times when a bird would want to fly high.
30Can you think of any?
31Before I go on, I'm curious.
32When would a bird need to fly high?
33Now would be a good time to pause the video and discuss.
34Okay, you ready?
35I don't know how you answered,
36but you may have mentioned that birds need to fly high to escape danger.
37And you're right!
38There are lots of animals, like foxes, coyotes, and even larger birds,
39that want to eat them for lunch.
40And flying high can keep them safe.
41I mean, when's the last time you saw a flying coyote?
42But that's not the only reason a bird might want to fly high.
43Each winter, certain types of birds fly thousands of miles, looking for better weather
44or just the right place to build a nest.
45It's called migration, and it's definitely not easy.
46It can take some birds more than a month to get to where they're trying to go.
47Imagine having to fly for that long!
48I'm getting tired just thinking about it.
49Luckily, flying high can help with that.
50For one thing, it's a lot cooler up there.
51Just like you and me, birds get hot when they move a lot.
52And the cold air up high can keep them from overheating from all that flapping.
53Another reason birds fly high during migration is wind.
54Wind can blow in different directions as you go up higher and higher.
55For example, down low, it can be blowing this way,
56but way up high, it might be blowing this way.
57If a bird wants to fly in the direction of those winds,
58they'll fly way up high to get to it.
59That way, the wind can help push them along,
60so they don't get as tired on the long trip.
61It's kind of like if a friend was pushing you on your bike,
62so you don't have to pedal as much.
63Oh, and get this:
64sometimes birds can even get pushed along by air that's moving up instead of sideways.
65Check this out.
66Notice how this bird is going higher and higher without flapping its wings?
67High-flying birds use towers of rising warm air, called thermals,
68to get higher and higher without getting tired.
69It's kind of like hopping on an elevator of air.
70You can actually observe birds using thermals on your own.
71Next time you're outside on a warm day,
72watch for birds flying in circles without flapping their wings.
73If they're getting higher and higher, they're probably circling in a thermal.
74Pretty cool!
75Because of energy-saving thermals and the power of their flapping wings,
76birds can fly pretty high when they need to.
77And when I say high, I'm not talking about this high
78or this high,
79or even this high.
80I'm talking way up there.
81I'm serious!
82Birds like whooper swans and even mallard ducks
83have been spotted flying over 20,000 feet.
84Mountain climbers have even reported seeing migrating birds, like the bar-headed geese,
85soar over some of the tallest mountains on Earth.
86And believe it or not,
87airplane pilots have even seen birds flying way higher than that.
88Like a type of Griffin vulture that was flying at 36,000 ft,
89the highest anyone's ever discovered a flying bird.
90Humans can't survive at altitudes like that unless they're in a warm plane.
91It's too cold, and there's not enough air to breathe.
92But amazingly, high-flying birds can.
93So in summary, birds fly high for a lot of reasons,
94like to escape from predators or to get a helpful push from the wind.
95High-flying birds like vultures and geese
96have been spotted flying higher than the tallest mountains on Earth,
97and even by pilots flying planes.
98Like this type of Griffin vulture that was reported flying at 36,000 ft,
99the highest a bird has ever been observed flying.
100That's all for this week's question.
101Thanks, Nova, for asking it!