1 00:00:10,400 --> 00:00:12,600 High flying, 2 00:00:12,600 --> 00:00:15,160 sharp-eyed, 3 00:00:15,160 --> 00:00:16,760 and fierce. 4 00:00:19,400 --> 00:00:21,600 From mountain tops 5 00:00:21,600 --> 00:00:24,080 to river valleys, 6 00:00:24,080 --> 00:00:26,160 eagles rule the skies. 7 00:00:28,160 --> 00:00:29,720 Tenacious and strong. 8 00:00:31,040 --> 00:00:33,200 They are the ultimate bird of prey. 9 00:00:36,800 --> 00:00:39,320 Now, for the first time... 10 00:00:41,560 --> 00:00:45,840 ..we'll follow the dramatic story of a wild bald eagle family... 11 00:00:48,440 --> 00:00:50,520 ..witness eagles in action... 12 00:00:52,920 --> 00:00:56,680 ..and join one man and his feathered friend 13 00:00:56,680 --> 00:01:00,440 to put these icons of the air to the test. 14 00:01:00,440 --> 00:01:02,680 Woohoo! What a girl! 15 00:01:03,720 --> 00:01:05,160 We'll reveal what it takes... 16 00:01:06,840 --> 00:01:09,480 ..and even what it feels like... 17 00:01:09,480 --> 00:01:12,640 Wow! We're flying with a golden eagle! 18 00:01:12,640 --> 00:01:16,680 ..to be the most powerful bird in the sky. 19 00:01:29,680 --> 00:01:32,760 This is Iowa in the American Midwest... 20 00:01:37,560 --> 00:01:39,840 ..and in the midst of a late winter snowfall... 21 00:01:39,840 --> 00:01:42,280 CHIRPING 22 00:01:42,280 --> 00:01:46,040 ..a bald eagle is trying to look after her most precious possessions. 23 00:01:52,440 --> 00:01:56,880 These two eggs must be kept at around 37 degrees Celsius 24 00:01:56,880 --> 00:01:58,720 if they are to hatch. 25 00:02:02,960 --> 00:02:06,880 At night, temperatures plummet to minus 25. 26 00:02:11,520 --> 00:02:14,960 By day, it's still cold enough to freeze her eyelashes. 27 00:02:17,400 --> 00:02:21,080 But she'll do whatever it takes to keep these eggs safe. 28 00:02:25,240 --> 00:02:30,240 Over the next few months, we'll follow them around the clock 29 00:02:30,240 --> 00:02:34,160 and see what it takes to become a superpowered eagle. 30 00:02:48,560 --> 00:02:52,280 Bald eagles are just one of 70 different species. 31 00:02:56,240 --> 00:02:58,240 They can look very different... 32 00:03:00,640 --> 00:03:04,160 ..but they all share a mesmerising blend of power... 33 00:03:05,880 --> 00:03:07,400 ..and beauty. 34 00:03:09,640 --> 00:03:12,680 They've mastered habitats across the planet. 35 00:03:14,520 --> 00:03:19,160 From harpy eagles in the rainforests of South America 36 00:03:19,160 --> 00:03:22,200 to Steller's sea eagles in the icy North Pacific. 37 00:03:24,400 --> 00:03:27,520 And fish eagles in the Great Lakes of Africa. 38 00:03:29,960 --> 00:03:31,760 They live at the top of the food chain... 39 00:03:34,200 --> 00:03:37,440 ..but to dominate their world, they must overcome 40 00:03:37,440 --> 00:03:39,480 some significant challenges. 41 00:03:41,760 --> 00:03:45,400 They have to cover hundreds of miles on the wing, 42 00:03:45,400 --> 00:03:48,840 spot their food at vast distances, 43 00:03:48,840 --> 00:03:53,120 and tackle the largest prey of any bird species. 44 00:03:56,560 --> 00:03:59,200 BIRDS CALLING 45 00:03:59,200 --> 00:04:01,720 To find out how eagles achieve this... 46 00:04:05,480 --> 00:04:08,320 ..we need to meet a remarkable bird. 47 00:04:19,920 --> 00:04:21,960 This is Tilly. 48 00:04:23,840 --> 00:04:27,840 A golden eagle with a wingspan of almost two metres. 49 00:04:29,880 --> 00:04:32,520 But what makes her unique is the relationship 50 00:04:32,520 --> 00:04:34,600 she has with her lifelong partner. 51 00:04:36,200 --> 00:04:38,600 Bird specialist Lloyd Buck. 52 00:04:41,800 --> 00:04:43,120 Hello! 53 00:04:43,120 --> 00:04:45,080 Hello, my love! 54 00:04:45,080 --> 00:04:47,360 Are you enjoying yourself, eh? 55 00:04:47,360 --> 00:04:49,040 You're the best, ain't ya? 56 00:04:49,040 --> 00:04:52,160 You're a once-in-a-lifetime bird, you are. Eh? 57 00:04:52,160 --> 00:04:55,240 I'll never have another bird like you ever, will I? 58 00:04:56,880 --> 00:04:59,320 Since he was a child, 59 00:04:59,320 --> 00:05:01,480 Lloyd has been obsessed with birds. 60 00:05:04,600 --> 00:05:08,560 Over the years, he's kept and trained many different species. 61 00:05:11,120 --> 00:05:13,760 But one stands out. 62 00:05:13,760 --> 00:05:14,960 Tilly. 63 00:05:16,600 --> 00:05:20,040 They've been together for 20 years, 64 00:05:20,040 --> 00:05:23,480 and have forged an exceptionally close bond. 65 00:05:27,960 --> 00:05:30,200 As far as Tilly is concerned, 66 00:05:30,200 --> 00:05:32,640 Lloyd is her mate for life. 67 00:05:32,640 --> 00:05:35,240 Go on! Go and enjoy yourself, my love. 68 00:05:36,400 --> 00:05:37,880 I wish I was you. 69 00:05:38,920 --> 00:05:40,160 I wish I was you! 70 00:05:42,480 --> 00:05:45,000 Thanks to Lloyd's dedicated work with Tilly, 71 00:05:45,000 --> 00:05:47,480 she acts just like a wild eagle, 72 00:05:47,480 --> 00:05:51,520 but is also comfortable around scientific equipment and cameras. 73 00:05:52,880 --> 00:05:55,680 So this is an extraordinary opportunity to learn 74 00:05:55,680 --> 00:05:58,040 more about these iconic animals. 75 00:06:00,600 --> 00:06:02,880 Eagles are such inspirational birds. 76 00:06:04,320 --> 00:06:07,840 There's so much I think that we don't understand about them, 77 00:06:07,840 --> 00:06:10,280 and that's what I'm hoping to learn here. 78 00:06:10,280 --> 00:06:13,040 A little window into her world, into the world of eagles. 79 00:06:16,960 --> 00:06:21,720 Together, Lloyd and Tilly will take on a series of tests 80 00:06:21,720 --> 00:06:25,040 that will unlock the eagle's remarkable powers. 81 00:06:33,160 --> 00:06:36,480 On the other side of the world, in Iowa, 82 00:06:36,480 --> 00:06:38,960 the adult female seems restless. 83 00:06:42,040 --> 00:06:44,720 One of the eggs is starting to hatch. 84 00:06:53,240 --> 00:06:57,320 From its first moments, the chick must show its strength. 85 00:06:59,040 --> 00:07:03,600 It uses a tiny egg tooth on top of its beak to crack the shell. 86 00:07:07,920 --> 00:07:09,960 CHICKS CHEEPING 87 00:07:27,800 --> 00:07:29,440 Three days later, 88 00:07:29,440 --> 00:07:31,880 it's joined by its sibling. 89 00:07:37,760 --> 00:07:39,760 At this age, they need to eat 90 00:07:39,760 --> 00:07:43,040 almost half their body weight in meat every day. 91 00:07:47,320 --> 00:07:49,240 Thankfully, help is on hand, 92 00:07:49,240 --> 00:07:51,760 and he's bringing fresh supplies. 93 00:07:55,240 --> 00:08:00,680 As with all bald eagles, the male is about 20% smaller than his mate. 94 00:08:03,840 --> 00:08:06,520 It's thought she might be bigger to help produce 95 00:08:06,520 --> 00:08:08,240 and incubate the young. 96 00:08:11,280 --> 00:08:13,920 Bald eagles normally pair for life, 97 00:08:13,920 --> 00:08:18,040 but this female's previous partner disappeared, 98 00:08:18,040 --> 00:08:19,920 so this male is new. 99 00:08:23,520 --> 00:08:26,400 The breeding season can last around ten months, 100 00:08:26,400 --> 00:08:30,160 so rearing these chicks will be a test of their new relationship. 101 00:08:33,840 --> 00:08:36,720 The chicks' weight needs to increase 102 00:08:36,720 --> 00:08:40,400 by a staggering 500% in the first week, 103 00:08:40,400 --> 00:08:44,000 so the adults spend much of the time out hunting. 104 00:08:56,880 --> 00:08:59,800 Bald eagles specialise in catching fish. 105 00:09:01,240 --> 00:09:03,920 They can make up to 90% of their diet. 106 00:09:10,760 --> 00:09:14,400 They're able to pluck them from the water 107 00:09:14,400 --> 00:09:16,200 with remarkable precision. 108 00:09:28,800 --> 00:09:30,240 CHEEPING 109 00:09:30,240 --> 00:09:34,160 But rabbits and squirrels are also delivered to the nest. 110 00:09:37,000 --> 00:09:38,680 For now at least, 111 00:09:38,680 --> 00:09:42,400 this partnership is providing all the food the chicks could need. 112 00:09:52,040 --> 00:09:56,080 Eagles around the world catch a wide variety of prey, 113 00:09:56,080 --> 00:09:58,520 so they have a range of hunting techniques... 114 00:10:02,000 --> 00:10:06,120 ..and one species has come up with an extraordinary strategy. 115 00:10:11,520 --> 00:10:13,600 The mountains of Oman. 116 00:10:17,040 --> 00:10:20,520 In this desert realm, food is hard to come by. 117 00:10:25,120 --> 00:10:28,400 But this Verreaux's eagle has a family to feed. 118 00:10:34,280 --> 00:10:37,720 Other birds dive-bomb the predator, 119 00:10:37,720 --> 00:10:39,560 hoping to chase it away. 120 00:10:47,480 --> 00:10:50,840 But this eagle is focused on a terrestrial target. 121 00:10:53,640 --> 00:10:55,120 Rock hyrax. 122 00:10:57,040 --> 00:11:00,080 These small mammals are equipped with special vision. 123 00:11:02,560 --> 00:11:05,360 A shield on their iris cuts out glare, 124 00:11:05,360 --> 00:11:07,600 helping them spot predators, 125 00:11:07,600 --> 00:11:09,200 even in bright sunlight. 126 00:11:11,200 --> 00:11:13,360 But one eagle is just a decoy. 127 00:11:14,920 --> 00:11:18,280 Verreaux's eagles hunt in pairs. 128 00:11:20,800 --> 00:11:23,040 The first flies in plain sight, 129 00:11:23,040 --> 00:11:24,800 distracting the hyrax... 130 00:11:28,320 --> 00:11:31,960 ..while the second eagle hugs the contours of the land, 131 00:11:31,960 --> 00:11:33,400 staying hidden... 132 00:11:35,520 --> 00:11:37,040 ..until the last moment. 133 00:11:39,000 --> 00:11:42,400 Using teamwork is devastatingly effective. 134 00:11:50,120 --> 00:11:52,600 But catching their quarry is a dangerous task. 135 00:11:55,520 --> 00:11:57,360 There's no room for error. 136 00:12:02,880 --> 00:12:06,520 When eagles hunt airborne prey, if something goes wrong 137 00:12:06,520 --> 00:12:09,960 they usually have space and time to get out of trouble. 138 00:12:12,400 --> 00:12:15,840 They can even escape a glancing blow with the water surface. 139 00:12:18,120 --> 00:12:20,720 But when the prey is on hard ground... 140 00:12:22,960 --> 00:12:26,400 ..one wrong move could result in a deadly collision. 141 00:12:31,360 --> 00:12:34,600 Especially when hunting a large, heavy animal. 142 00:12:46,320 --> 00:12:49,320 There's simply no scope to make a mistake. 143 00:12:58,680 --> 00:13:03,200 So how do eagles target and safely catch terrestrial prey? 144 00:13:06,000 --> 00:13:09,480 To find out, Lloyd has come to Scotland 145 00:13:09,480 --> 00:13:12,840 to put his golden eagle Tilly to the test. 146 00:13:16,920 --> 00:13:18,400 But first, 147 00:13:18,400 --> 00:13:21,000 he needs something for her to hunt. 148 00:13:24,280 --> 00:13:26,920 This is Robohare. 149 00:13:30,840 --> 00:13:34,440 Designed and created by tech wizard Chris Watts. 150 00:13:34,440 --> 00:13:36,120 With a fake fur coat 151 00:13:36,120 --> 00:13:39,360 and high-speed motors, it can blend into the undergrowth 152 00:13:39,360 --> 00:13:41,400 or flash across the open. 153 00:13:43,400 --> 00:13:47,920 It's also fitted with an onboard 360 camera to capture all of the action. 154 00:13:49,680 --> 00:13:51,880 OK. She's going to rouse. Get ready. 155 00:13:53,040 --> 00:13:55,960 OK. Go! Go! Go! Fire! Fire! 156 00:13:55,960 --> 00:13:58,720 In a matter of seconds, Tilly locks on to her target. 157 00:14:02,680 --> 00:14:04,720 She's got him. She's done it. 158 00:14:04,720 --> 00:14:06,560 Thank you very much, Tilly. 159 00:14:06,560 --> 00:14:07,560 Good girl! 160 00:14:08,800 --> 00:14:11,840 To challenge Tilly's hunting ability, 161 00:14:11,840 --> 00:14:13,480 they repeat the test 162 00:14:13,480 --> 00:14:15,080 in different conditions. 163 00:14:15,080 --> 00:14:16,680 Go! 164 00:14:16,680 --> 00:14:20,160 From strong winds and overcast skies 165 00:14:20,160 --> 00:14:21,600 to bright sunlight. 166 00:14:26,520 --> 00:14:28,160 But the outcome is the same. 167 00:14:35,320 --> 00:14:37,720 To reveal the secret to her success, 168 00:14:37,720 --> 00:14:41,440 we need to go through the footage frame by frame. 169 00:14:45,160 --> 00:14:49,800 First, Tilly keeps a constant lock on Robohare's position. 170 00:14:52,880 --> 00:14:56,880 Next, she uses her wings to adjust her trajectory 171 00:14:56,880 --> 00:14:59,120 as the wind changes 172 00:14:59,120 --> 00:15:00,760 or the target moves. 173 00:15:05,760 --> 00:15:09,640 She keeps her legs tucked in to stay aerodynamic. 174 00:15:09,640 --> 00:15:12,360 Then, just a quarter of a second before impact, 175 00:15:12,360 --> 00:15:15,840 she swings her feet forwards 176 00:15:15,840 --> 00:15:18,040 so both eyes can see Robohare 177 00:15:18,040 --> 00:15:19,800 AND her talons. 178 00:15:20,920 --> 00:15:22,640 She makes perfect contact. 179 00:15:27,360 --> 00:15:30,280 But in a demonstration of sheer power... 180 00:15:30,280 --> 00:15:31,840 OK, get ready, Chris. 181 00:15:31,840 --> 00:15:35,680 ..Tilly's hunting skill is about to reach the next level. 182 00:15:42,240 --> 00:15:45,280 Robohare weighs 5.8 kilos - 183 00:15:45,280 --> 00:15:48,120 one and a half times more than Tilly. 184 00:15:58,040 --> 00:16:00,720 But not only can she catch Robohare... 185 00:16:04,360 --> 00:16:06,800 ..she can lift it high into the air. 186 00:16:09,240 --> 00:16:12,520 She even has the strength to carry it with one foot. 187 00:16:14,760 --> 00:16:19,280 A remarkable achievement for a load weighing 150% 188 00:16:19,280 --> 00:16:21,000 of her own body weight. 189 00:16:22,200 --> 00:16:24,600 Yes! Woohoo-hoo! 190 00:16:24,600 --> 00:16:26,920 What a girl! 191 00:16:26,920 --> 00:16:28,760 Good bird! There's a good eagle! 192 00:16:30,400 --> 00:16:34,240 She's able to do this because, like all eagles, 193 00:16:34,240 --> 00:16:38,480 she's armed with highly specialised weapons - talons. 194 00:16:52,880 --> 00:16:56,160 and inflict fatal damage upon their victim... 195 00:16:58,360 --> 00:17:01,840 ..while the beak is used to cut up the meal. 196 00:17:04,600 --> 00:17:08,560 The harpy eagle has some of the largest talons in the world, 197 00:17:08,560 --> 00:17:13,040 measuring up to 12 centimetres - twice as long as a golden eagle's. 198 00:17:15,680 --> 00:17:19,600 These weapons can suffocate their quarry 199 00:17:19,600 --> 00:17:22,760 or create puncture wounds and blood loss. 200 00:17:26,240 --> 00:17:30,920 To achieve this, eagles must grip with enormous force 201 00:17:30,920 --> 00:17:35,200 and hold this pressure for a long time, without tiring. 202 00:17:38,640 --> 00:17:41,240 So they rely on some clever mechanics. 203 00:17:45,320 --> 00:17:48,040 Their feet have an in-built ratchet system. 204 00:17:51,400 --> 00:17:53,960 The tendons in their toes are ridged 205 00:17:53,960 --> 00:17:56,040 and so is the tissue around it. 206 00:17:57,920 --> 00:18:00,640 This creates a simple locking mechanism 207 00:18:00,640 --> 00:18:03,200 so the surrounding muscles can relax 208 00:18:03,200 --> 00:18:05,360 without losing any grip force. 209 00:18:08,280 --> 00:18:10,720 Many birds have this adaptation, 210 00:18:10,720 --> 00:18:12,720 but in eagles the ridges are 211 00:18:12,720 --> 00:18:14,760 particularly large, to cope 212 00:18:14,760 --> 00:18:16,560 with the enormous power. 213 00:18:20,880 --> 00:18:23,520 Creating and maintaining such a high force 214 00:18:23,520 --> 00:18:25,920 is a critical part of their success. 215 00:18:29,600 --> 00:18:32,680 And it helps them take down even the largest prey. 216 00:18:38,440 --> 00:18:42,840 But these super-strong weapons have a second essential purpose. 217 00:18:45,040 --> 00:18:46,280 To fight. 218 00:18:54,400 --> 00:18:57,600 Winter in the Alps can be desperately bleak. 219 00:19:02,520 --> 00:19:05,760 Golden eagles soar across the peaks in search of prey. 220 00:19:07,440 --> 00:19:09,960 And when food is scarce, 221 00:19:09,960 --> 00:19:12,280 they have to turn to scavenging. 222 00:19:16,520 --> 00:19:18,600 SQUAWKING 223 00:19:24,040 --> 00:19:25,480 A dead fox. 224 00:19:27,080 --> 00:19:29,680 It could last this female eagle for days. 225 00:19:32,200 --> 00:19:35,520 Such a prized meal is in demand. 226 00:19:35,520 --> 00:19:40,720 This devious mob of crows will try anything to steal a mouthful. 227 00:19:45,880 --> 00:19:50,560 A flash of talons reminds them who's at the top of the food chain. 228 00:20:01,960 --> 00:20:04,600 But the biggest threat 229 00:20:04,600 --> 00:20:06,320 comes from her own kind. 230 00:20:38,240 --> 00:20:41,040 A meal like this is worth fighting for. 231 00:20:43,280 --> 00:20:46,760 In battle, talons are their weapons of choice. 232 00:20:49,360 --> 00:20:53,000 They use their long legs to keep their head, and importantly 233 00:20:53,000 --> 00:20:55,240 their eyes, away from danger. 234 00:21:01,320 --> 00:21:03,320 Using their talons effectively 235 00:21:03,320 --> 00:21:06,840 can make all the difference in who loses 236 00:21:06,840 --> 00:21:08,560 and who survives. 237 00:21:23,280 --> 00:21:24,720 In Iowa... 238 00:21:26,320 --> 00:21:30,600 ..our bald eagle youngsters are now one and a half weeks old. 239 00:21:33,240 --> 00:21:35,880 Thanks to the hunting skill of their parents, 240 00:21:35,880 --> 00:21:38,520 they're gaining about 10% in weight each day. 241 00:21:42,320 --> 00:21:46,120 Their talons develop quicker than other parts of their body, 242 00:21:46,120 --> 00:21:48,080 showing how important they are. 243 00:21:49,880 --> 00:21:53,360 But it will be another three months before they have proper control 244 00:21:53,360 --> 00:21:55,360 of these formidable weapons. 245 00:21:58,000 --> 00:22:01,360 For now, they're almost completely defenceless... 246 00:22:04,320 --> 00:22:07,360 ..and the slightest thing can pose a threat. 247 00:22:12,760 --> 00:22:17,520 Somehow, one has become tangled in the female's feathers 248 00:22:17,520 --> 00:22:19,560 and it's at risk of choking. 249 00:22:19,560 --> 00:22:21,520 CHEEPING 250 00:22:24,680 --> 00:22:27,040 It's hard to know how this has happened. 251 00:22:36,640 --> 00:22:41,200 And the female seems confused and stressed. 252 00:22:50,640 --> 00:22:52,440 The more she moves around, 253 00:22:52,440 --> 00:22:55,080 the more she pulls on the chick's neck. 254 00:23:13,080 --> 00:23:15,440 A lucky escape, 255 00:23:15,440 --> 00:23:18,440 but now it's stuck on its back 256 00:23:18,440 --> 00:23:21,840 and the male seems distracted by the other chick. 257 00:23:25,440 --> 00:23:29,040 Less than half of all bald eagle chicks survive their first year. 258 00:23:32,240 --> 00:23:34,320 The odds may be against it, 259 00:23:34,320 --> 00:23:38,160 but this time, those powerful talons come to the rescue. 260 00:23:43,960 --> 00:23:45,880 When it comes to growing up, 261 00:23:45,880 --> 00:23:50,760 the gamble of life or death for some eagle species is even greater. 262 00:23:52,440 --> 00:23:54,600 THUNDER RUMBLES 263 00:24:00,720 --> 00:24:02,320 Zambia. 264 00:24:06,000 --> 00:24:07,800 Home to the crowned eagle. 265 00:24:12,680 --> 00:24:16,120 They are known as the most powerful eagles in Africa. 266 00:24:17,760 --> 00:24:20,400 THUNDER AND LIGHTNING 267 00:24:20,400 --> 00:24:24,680 This adult has chosen to nest in a small patch of swamp forest, 268 00:24:24,680 --> 00:24:27,440 and is trying to raise a single chick. 269 00:24:30,960 --> 00:24:35,040 The eaglet needs to eat 30% of its body weight in meat each day. 270 00:24:37,280 --> 00:24:38,680 But right now 271 00:24:38,680 --> 00:24:41,520 there's just not enough food here to support a family. 272 00:24:44,720 --> 00:24:49,120 Nesting here seems like a big miscalculation, 273 00:24:49,120 --> 00:24:51,800 but there's a reason behind taking this risk. 274 00:24:58,000 --> 00:25:01,640 What this forest does hold are fruit trees... 275 00:25:04,760 --> 00:25:06,840 ..and the fruit is ripe for harvest. 276 00:25:10,320 --> 00:25:13,040 It's of no use to the eagles, 277 00:25:13,040 --> 00:25:15,840 but it's vital for another animal. 278 00:25:18,000 --> 00:25:19,680 HIGH-PITCHED CALLS 279 00:25:19,680 --> 00:25:21,120 Fruit bats. 280 00:25:24,600 --> 00:25:27,040 Ten million arrive here each year. 281 00:25:29,200 --> 00:25:33,120 It's the largest mammal migration in Africa, 282 00:25:33,120 --> 00:25:36,400 and exactly what the eagles are waiting for. 283 00:25:42,680 --> 00:25:44,720 They target individual bats, 284 00:25:44,720 --> 00:25:47,000 picking them out from the swarm. 285 00:25:49,560 --> 00:25:52,640 Fish eagles and martial eagles join the hunt. 286 00:26:13,800 --> 00:26:18,160 The bats will be here for up to 90 days, 287 00:26:18,160 --> 00:26:21,280 providing food for the chick at its most vulnerable age. 288 00:26:28,120 --> 00:26:31,400 Timing their breeding cycle with the bats' arrival is a risk... 289 00:26:33,640 --> 00:26:37,080 ..but for this crowned eagle family, it's paid off. 290 00:26:49,040 --> 00:26:51,640 In Iowa, it's spring. 291 00:26:54,680 --> 00:26:57,000 The adult eagles are delivering 292 00:26:57,000 --> 00:26:59,440 around five fish a day to the nest. 293 00:27:01,080 --> 00:27:03,160 Now four weeks old, 294 00:27:03,160 --> 00:27:04,920 the chicks are changing. 295 00:27:10,440 --> 00:27:14,680 Their fluffy, warm down is peppered with juvenile flight feathers. 296 00:27:23,000 --> 00:27:26,880 But perhaps the most important change is in their vision. 297 00:27:28,680 --> 00:27:31,360 Their eyes open within hours of hatching. 298 00:27:31,360 --> 00:27:36,200 But much like a human baby, they're born with poor sight. 299 00:27:37,640 --> 00:27:40,400 It takes time for it to sharpen 300 00:27:40,400 --> 00:27:44,760 and become one of the most powerful senses in the animal world. 301 00:27:55,880 --> 00:27:59,760 We describe anyone with exceptional sight as eagle-eyed. 302 00:28:02,840 --> 00:28:05,040 But just how good is eagle vision? 303 00:28:08,920 --> 00:28:11,560 To put it to the test, 304 00:28:11,560 --> 00:28:15,560 Lloyd Buck and his golden eagle Tilly 305 00:28:15,560 --> 00:28:18,280 are entering a remote part of Scotland. 306 00:28:27,640 --> 00:28:31,880 They're joined by Professor Graham Martin, 307 00:28:31,880 --> 00:28:33,720 an expert in avian vision. 308 00:28:35,920 --> 00:28:39,840 To compare the basics of eagle and human eyesight, 309 00:28:39,840 --> 00:28:41,640 Graham has a demonstration. 310 00:28:44,080 --> 00:28:47,120 We're going to have some sort of measure of our acuity, how much 311 00:28:47,120 --> 00:28:50,680 detail that we can see, using the black and white stripes, equally 312 00:28:50,680 --> 00:28:53,040 spaced apart, called a grating. 313 00:28:53,040 --> 00:28:57,880 And our task is simply to back away from this and come to the point 314 00:28:57,880 --> 00:29:00,040 when we can't see the stripes any more, 315 00:29:00,040 --> 00:29:03,280 and then that's our threshold for seeing detailed vision. 316 00:29:04,600 --> 00:29:06,600 As they walk further away, 317 00:29:06,600 --> 00:29:09,400 the black and white stripes become less clear, 318 00:29:09,400 --> 00:29:11,800 and then merge to become a grey blur. 319 00:29:13,520 --> 00:29:15,000 I'm just about the limit now. 320 00:29:15,000 --> 00:29:16,160 Yeah, I'm there now. 321 00:29:16,160 --> 00:29:17,360 You're there? Yeah. 322 00:29:17,360 --> 00:29:18,720 I'm still all right. 323 00:29:21,840 --> 00:29:23,280 That's me. 324 00:29:23,280 --> 00:29:25,320 Here I am. Nine metres. 325 00:29:26,600 --> 00:29:28,360 Nine metres? Yep. 326 00:29:28,360 --> 00:29:31,200 I'm just under 13 and a half metres. 327 00:29:32,600 --> 00:29:35,040 Eyesight deteriorates with age, 328 00:29:35,040 --> 00:29:39,080 so it's no surprise that Lloyd has greater visual acuity, 329 00:29:39,080 --> 00:29:43,160 but how do scientists think an eagle like Tilly would fare? 330 00:29:43,160 --> 00:29:44,880 The experiments that have been done 331 00:29:44,880 --> 00:29:48,280 show that they're about five times better than us. 332 00:29:48,280 --> 00:29:50,600 Five times that, it's somewhere right up there. 333 00:29:50,600 --> 00:29:52,120 The end of the tape. 334 00:29:53,120 --> 00:29:54,760 This seems impressive, 335 00:29:54,760 --> 00:29:58,200 but what does it mean for an eagle hunting in the wild? 336 00:30:02,920 --> 00:30:08,000 To find out, Lloyd and Graham have planned a game of hide and seek 337 00:30:08,000 --> 00:30:09,800 on an epic scale. 338 00:30:13,040 --> 00:30:15,680 Tilly must find Lloyd somewhere in this landscape. 339 00:30:18,080 --> 00:30:21,680 Her cage has been covered so she can't cheat, 340 00:30:21,680 --> 00:30:26,720 and Lloyd has found a position 400 metres away. 341 00:30:29,000 --> 00:30:32,120 RADIO: OK, I'm going to release her now. OK. 342 00:30:40,160 --> 00:30:41,680 OK, Lloyd, she's gone. 343 00:30:45,040 --> 00:30:49,680 Tilly immediately scans the landscape in search of Lloyd. 344 00:30:49,680 --> 00:30:51,440 Moving your way now, 345 00:30:51,440 --> 00:30:53,040 at great speed, actually. 346 00:31:06,600 --> 00:31:09,080 She's actually found you in no time at all. 347 00:31:09,080 --> 00:31:11,120 Good girl! 348 00:31:11,120 --> 00:31:12,760 You're beautiful, aren't you? 349 00:31:14,200 --> 00:31:17,240 Tilly spotted Lloyd from 400 metres away, 350 00:31:17,240 --> 00:31:20,160 but Graham thinks that was far too easy. 351 00:31:21,160 --> 00:31:22,720 She was so quickly onto you, 352 00:31:22,720 --> 00:31:25,960 I don't think it was really much of a challenge for her, in a way. 353 00:31:25,960 --> 00:31:28,040 If you wanted to, I think we could push the distance. 354 00:31:28,040 --> 00:31:29,200 What do you think? 355 00:31:29,200 --> 00:31:30,880 OK, that sounds really good. 356 00:31:32,520 --> 00:31:35,520 Lloyd repositions himself for a much bigger challenge. 357 00:31:37,320 --> 00:31:39,840 He's now one and a half miles away 358 00:31:39,840 --> 00:31:42,040 on the opposite side of the glen, 359 00:31:42,040 --> 00:31:44,240 and the weather conditions are not ideal. 360 00:31:45,920 --> 00:31:48,520 Even with a powerful telephoto lens, 361 00:31:48,520 --> 00:31:51,160 it's hard to pick out Graham and Tilly. 362 00:31:51,160 --> 00:31:53,560 It's a long way. 363 00:31:53,560 --> 00:31:57,160 I cannot see you without a pair of binoculars, and even 364 00:31:57,160 --> 00:32:00,040 with the binoculars, there's that much moisture in the air, 365 00:32:00,040 --> 00:32:03,880 so this is a real challenge for Tilly. 366 00:32:03,880 --> 00:32:05,960 OK, then. Well, I'll release her now. 367 00:32:05,960 --> 00:32:07,240 OK? 368 00:32:07,240 --> 00:32:08,440 OK. Good luck. 369 00:32:08,440 --> 00:32:10,240 Come on, Tilly. Come on, Tills. 370 00:32:12,720 --> 00:32:13,840 She's off. 371 00:32:15,960 --> 00:32:17,760 She's looking very hard. 372 00:32:19,840 --> 00:32:21,600 I'm sure she's trying to find you. 373 00:32:23,040 --> 00:32:25,880 Tilly has never faced a challenge like this, 374 00:32:25,880 --> 00:32:30,040 but she starts to make her way to the other side of the glen. 375 00:32:30,040 --> 00:32:32,720 Come on, Tilly! Come on! 376 00:32:32,720 --> 00:32:34,480 HE LAUGHS 377 00:32:36,000 --> 00:32:39,560 Interestingly, she takes an indirect route, 378 00:32:39,560 --> 00:32:42,760 riding a series of strong air currents to reach Lloyd 379 00:32:42,760 --> 00:32:44,800 more efficiently... 380 00:32:44,800 --> 00:32:46,400 ..and more quickly. 381 00:32:47,840 --> 00:32:51,280 She's coming in! She's coming in fast! Woohoo! 382 00:32:51,280 --> 00:32:52,600 She's done it, Graham. 383 00:32:52,600 --> 00:32:55,200 Absolutely hammering across the valley! 384 00:32:55,200 --> 00:32:57,800 Yee-hoo! What a bird she is! 385 00:33:05,480 --> 00:33:08,000 You clever bird! 386 00:33:08,000 --> 00:33:09,960 Woohoo! 387 00:33:09,960 --> 00:33:12,120 What an eagle you are, hey? 388 00:33:12,120 --> 00:33:13,280 Hello! 389 00:33:13,280 --> 00:33:15,640 LAUGHS 390 00:33:15,640 --> 00:33:18,200 Graham, she's on my arm. 391 00:33:18,200 --> 00:33:20,320 That is absolutely incredible. 392 00:33:20,320 --> 00:33:23,760 I'm so pleased with her. I've never asked her to find me like that. 393 00:33:23,760 --> 00:33:26,520 That is actually very, very impressive because it took 394 00:33:26,520 --> 00:33:28,440 really very little time at all. 395 00:33:30,160 --> 00:33:33,520 Tilly spotted Lloyd in this vast landscape 396 00:33:33,520 --> 00:33:36,520 from one and a half miles away, 397 00:33:36,520 --> 00:33:38,200 a feat so impressive 398 00:33:38,200 --> 00:33:40,760 it seems almost superpowered. 399 00:33:41,840 --> 00:33:43,880 So how does she achieve this? 400 00:33:46,320 --> 00:33:50,600 Images are projected onto the retina at the back of the eagle's eye. 401 00:33:53,800 --> 00:33:55,880 This area is covered with 402 00:33:55,880 --> 00:33:57,880 light-sensitive cells 403 00:33:57,880 --> 00:34:00,200 known as cones. The more cones, 404 00:34:00,200 --> 00:34:02,160 the sharper the eyesight. 405 00:34:03,680 --> 00:34:08,680 A human eye may have 200,000 cones per square millimetre, 406 00:34:08,680 --> 00:34:10,960 but eagles have over twice as many, 407 00:34:10,960 --> 00:34:13,320 giving them the sharpest eyesight 408 00:34:13,320 --> 00:34:15,120 of any vertebrate animal. 409 00:34:19,400 --> 00:34:24,200 The eagle's supreme visual acuity gives them a significant advantage. 410 00:34:26,360 --> 00:34:29,920 It means they can quickly pick out prey in a vast landscape. 411 00:34:31,880 --> 00:34:36,880 But there's an unexpected downside to having such sharp vision. 412 00:34:36,880 --> 00:34:41,000 The problem is, you don't want to get the sun in your eyes. 413 00:34:41,000 --> 00:34:43,800 It would destroy all the very high acuity it's got. 414 00:34:43,800 --> 00:34:46,960 So they have these big eyebrows. It's like wearing a baseball cap! 415 00:34:46,960 --> 00:34:49,280 That's all designed to keep the sun out their eyes, 416 00:34:49,280 --> 00:34:51,320 so they don't actually ever image the sun. 417 00:34:52,760 --> 00:34:56,640 This brow ridge is what gives eagles their fearsome stare. 418 00:34:58,080 --> 00:35:00,480 But it has a serious drawback. 419 00:35:02,120 --> 00:35:04,440 Of course, if you're keeping the sun out your eyes, 420 00:35:04,440 --> 00:35:06,360 you can't actually see what's up there. 421 00:35:06,360 --> 00:35:09,160 What an eagle wants to do is patrol and look down 422 00:35:09,160 --> 00:35:12,880 at the big terrain below it, and it's bending its head forward. 423 00:35:12,880 --> 00:35:15,280 It's tipping its head down to have a look. 424 00:35:15,280 --> 00:35:16,840 And that means that this blind area, 425 00:35:16,840 --> 00:35:18,800 which is designed to keep the sun out their eyes, 426 00:35:18,800 --> 00:35:21,240 is stopping them actually looking where they're going. 427 00:35:23,200 --> 00:35:25,240 This blind spot isn't usually a problem. 428 00:35:27,000 --> 00:35:30,120 In their natural habitat, they soar high above the trees. 429 00:35:33,080 --> 00:35:35,120 But in a modern landscape, 430 00:35:35,120 --> 00:35:36,800 it can be a fatal flaw. 431 00:35:38,880 --> 00:35:41,520 Across the world, eagles are colliding 432 00:35:41,520 --> 00:35:43,320 with man-made structures. 433 00:35:44,360 --> 00:35:47,880 Wind turbines, often built in wild landscapes, 434 00:35:47,880 --> 00:35:49,800 can be a particular issue. 435 00:35:51,920 --> 00:35:55,120 So at this wind farm in Wyoming, 436 00:35:55,120 --> 00:35:57,720 they've placed observation towers around the site... 437 00:35:59,600 --> 00:36:03,000 ..and if an eagle is spotted, they switch the turbines off. 438 00:36:06,920 --> 00:36:09,800 But in bright light, eagles can be hard to spot. 439 00:36:13,640 --> 00:36:18,240 So now they're using artificial intelligence to improve the odds. 440 00:36:21,320 --> 00:36:24,360 This technology harnesses ten cameras to spot 441 00:36:24,360 --> 00:36:26,200 and track flying objects. 442 00:36:29,240 --> 00:36:33,800 It can work out if the object is an eagle in just one second 443 00:36:33,800 --> 00:36:37,160 and temporarily shut down any turbines in its path. 444 00:36:41,480 --> 00:36:45,920 It's over five times more effective than humans, 445 00:36:45,920 --> 00:36:48,920 meaning the eagles here are now far safer. 446 00:36:59,360 --> 00:37:01,720 But elsewhere around the world, 447 00:37:01,720 --> 00:37:05,160 the biggest threat to most eagles is still humans. 448 00:37:10,480 --> 00:37:14,680 In the tropics, deforestation is threatening jungle species... 449 00:37:16,280 --> 00:37:18,800 ..like the Philippine eagle 450 00:37:18,800 --> 00:37:21,040 and the harpy eagle. 451 00:37:24,200 --> 00:37:27,520 There are fewer trees for them to nest in 452 00:37:27,520 --> 00:37:30,800 and far less prey for them to hunt. 453 00:37:35,200 --> 00:37:38,160 Many eagles also succumb to lead poisoning, 454 00:37:38,160 --> 00:37:41,440 as hunting ammunition contaminates carcasses. 455 00:37:45,000 --> 00:37:48,280 More than a third of all eagle species are considered 456 00:37:48,280 --> 00:37:50,520 to be endangered or vulnerable. 457 00:37:53,120 --> 00:37:57,600 But conservationists have proved in the past that, with the right help, 458 00:37:57,600 --> 00:38:01,040 some eagles can be saved from the brink of extinction. 459 00:38:05,920 --> 00:38:10,160 During the 1940s, DDT, a potent insecticide, 460 00:38:10,160 --> 00:38:12,200 was considered a wonder chemical. 461 00:38:14,440 --> 00:38:17,480 A solution to pest problems, large or small. 462 00:38:20,160 --> 00:38:23,200 It was even sprayed on people to rid them of parasites. 463 00:38:27,800 --> 00:38:32,120 Colourless and tasteless, DDT seeped into the ecosystems. 464 00:38:35,760 --> 00:38:38,640 At first no-one realised its impact, 465 00:38:38,640 --> 00:38:43,320 but the chemical passed from prey to predator, 466 00:38:43,320 --> 00:38:45,920 and those at the top were hit hardest, 467 00:38:45,920 --> 00:38:47,760 especially bald eagles. 468 00:38:50,440 --> 00:38:53,840 It caused a thinning in eagle egg shells, which meant 469 00:38:53,840 --> 00:38:56,120 they cracked during incubation... 470 00:38:58,200 --> 00:39:00,360 ..and it almost wiped them out. 471 00:39:05,440 --> 00:39:08,680 Eventually, DDT was banned 472 00:39:08,680 --> 00:39:11,320 and some heroic conservationists 473 00:39:11,320 --> 00:39:12,480 stepped up. 474 00:39:15,200 --> 00:39:17,520 Eggs were taken from the wild, 475 00:39:17,520 --> 00:39:19,880 hatched safely in captivity... 476 00:39:23,520 --> 00:39:27,760 ..and the chicks were returned to the nest to be reared naturally. 477 00:39:29,400 --> 00:39:31,040 And it worked. 478 00:39:35,480 --> 00:39:39,920 There are now thought to be over 140,000 bald eagles in the US. 479 00:39:41,680 --> 00:39:43,640 A truly remarkable comeback. 480 00:39:49,720 --> 00:39:54,600 Today, each new chick is still important to the growing population. 481 00:40:03,520 --> 00:40:07,440 In Iowa, the parents are doing well... 482 00:40:10,440 --> 00:40:15,320 ..providing their chicks with enough food to grow at a remarkable rate. 483 00:40:17,160 --> 00:40:18,960 Now eight weeks old, 484 00:40:18,960 --> 00:40:21,240 the eaglets are almost fully grown 485 00:40:21,240 --> 00:40:24,640 and covered with new dark brown feathers. 486 00:40:26,880 --> 00:40:30,760 But they are about to face their biggest survival challenge yet. 487 00:40:32,520 --> 00:40:34,800 FLIES BUZZING 488 00:40:34,800 --> 00:40:37,440 Something seems to be bothering them. 489 00:40:39,640 --> 00:40:43,120 A wet spring has created ideal conditions for an infestation 490 00:40:43,120 --> 00:40:46,080 of bloodsucking blackflies, 491 00:40:46,080 --> 00:40:48,640 and they are attacking the eaglets. 492 00:40:52,680 --> 00:40:57,560 The number of blackflies seems to be getting higher in this region, 493 00:40:57,560 --> 00:40:59,800 and this season is particularly bad. 494 00:41:03,720 --> 00:41:07,120 The chicks are growing weaker from the sheer number of bites. 495 00:41:08,720 --> 00:41:11,800 And, worse still, they're becoming restless. 496 00:41:20,320 --> 00:41:23,280 One youngster is so uncomfortable, 497 00:41:23,280 --> 00:41:26,120 it climbs the tree to get away. 498 00:41:28,440 --> 00:41:32,120 But the chick is 22 metres up, 499 00:41:32,120 --> 00:41:37,880 too young to fledge and too weak to deal with the strong wind. 500 00:41:41,680 --> 00:41:45,480 In sheer desperation, it leaps... 501 00:41:47,760 --> 00:41:49,360 ..and falls to the ground. 502 00:41:53,200 --> 00:41:56,400 The nest cameras lose sight of it, 503 00:41:56,400 --> 00:41:58,000 and so do the parents. 504 00:42:02,800 --> 00:42:06,640 This family's future now appears to rest with the remaining chick. 505 00:42:16,480 --> 00:42:20,240 But worryingly, it's also driven from the nest. 506 00:42:21,600 --> 00:42:23,320 CHEEPING 507 00:42:23,320 --> 00:42:25,120 FLIES BUZZING 508 00:42:28,560 --> 00:42:30,400 The parents are helpless. 509 00:42:43,720 --> 00:42:46,840 The chick doesn't yet have full control of its large feet... 510 00:42:49,080 --> 00:42:51,440 ..and one mistake is all it takes. 511 00:43:07,560 --> 00:43:09,960 The only hope for the eaglets now 512 00:43:09,960 --> 00:43:13,640 is that they'll be found somewhere beneath the nest. 513 00:43:18,920 --> 00:43:23,200 If the chicks were older they could have flown to safety, 514 00:43:23,200 --> 00:43:28,080 but it takes many weeks for a young eagle to truly master its wings. 515 00:43:30,920 --> 00:43:35,240 In fact, flight is probably the most sophisticated 516 00:43:35,240 --> 00:43:37,440 eagle superpower of all. 517 00:43:42,080 --> 00:43:43,880 Eagles dominate the sky. 518 00:43:46,880 --> 00:43:49,800 They can dive at over 150mph... 519 00:43:51,640 --> 00:43:55,520 ..and perform spectacular aerobatics when they fight 520 00:43:55,520 --> 00:43:57,080 or display to a mate. 521 00:43:59,760 --> 00:44:03,400 And one of their greatest aerial abilities is soaring. 522 00:44:07,400 --> 00:44:11,800 Golden eagles can have a home range of up to 2,000 square miles. 523 00:44:13,760 --> 00:44:18,040 To cover these vast distances, they use air currents to push them 524 00:44:18,040 --> 00:44:20,480 high into the air without flapping their wings... 525 00:44:23,560 --> 00:44:25,600 ..saving them precious energy. 526 00:44:32,280 --> 00:44:35,920 It's something Lloyd Buck has always wanted to know more about. 527 00:44:38,560 --> 00:44:40,200 So he's come to California, 528 00:44:40,200 --> 00:44:43,240 where paragliding fanatic Michael Vergalla 529 00:44:43,240 --> 00:44:46,240 often flies alongside wild birds of prey. 530 00:44:48,320 --> 00:44:52,200 By learning what it takes to fly a paraglider, Lloyd hopes 531 00:44:52,200 --> 00:44:55,480 he will understand more about how eagles soar. 532 00:44:55,480 --> 00:44:58,520 Bring the wing up in three, two, one... 533 00:44:58,520 --> 00:45:00,160 Wing's coming up. 534 00:45:03,960 --> 00:45:06,160 OK. Walk, walk, walk, walk. 535 00:45:06,160 --> 00:45:08,000 Start running. Run, run, run, run! 536 00:45:08,000 --> 00:45:09,560 Run, run, run, run, run. 537 00:45:22,560 --> 00:45:25,000 All right, Lloyd. OK. Here we go! 538 00:45:26,280 --> 00:45:28,720 We're flying! We're flying, Mike. 539 00:45:31,360 --> 00:45:32,600 Wow! 540 00:45:40,000 --> 00:45:43,560 I've seen Tilly do this so many times, and now I'm doing it. 541 00:45:43,560 --> 00:45:45,000 LAUGHS 542 00:45:48,240 --> 00:45:50,280 When eagles soar, they search 543 00:45:50,280 --> 00:45:53,320 for the strongest air currents to push them higher. 544 00:45:55,880 --> 00:45:58,440 Mike and Lloyd must do the same, 545 00:45:58,440 --> 00:46:01,040 so they look for tiny clues in the air 546 00:46:01,040 --> 00:46:03,880 and movement in the vegetation below. 547 00:46:05,000 --> 00:46:06,720 You're looking for changes. 548 00:46:06,720 --> 00:46:08,920 You're smelling, you're listening. 549 00:46:08,920 --> 00:46:11,000 You're trying to use all of your senses 550 00:46:11,000 --> 00:46:12,760 to figure out what's happening. 551 00:46:12,760 --> 00:46:14,840 Oh, look at the tree moving. Look at the tree moving. 552 00:46:14,840 --> 00:46:16,880 Yep. We're going to get a bump here. Ready? 553 00:46:18,200 --> 00:46:20,120 All right? So you're going to feel... 554 00:46:20,120 --> 00:46:21,960 I can feel it, I can feel it! 555 00:46:21,960 --> 00:46:23,360 There you go. Wow. 556 00:46:23,360 --> 00:46:26,120 And we're going to feel more as we get in here. Yeah. 557 00:46:26,120 --> 00:46:30,040 I can really feel the pressure, the change in it. 558 00:46:30,040 --> 00:46:34,160 Just like an eagle, Mike is trying to gain altitude by harnessing 559 00:46:34,160 --> 00:46:35,840 two common air currents. 560 00:46:39,040 --> 00:46:43,680 Thermals form as the sun heats the earth, 561 00:46:43,680 --> 00:46:47,320 which in turn warms the air above it, 562 00:46:47,320 --> 00:46:49,640 creating a rising column of air. 563 00:46:52,840 --> 00:46:55,680 Updrafts are created when horizontal winds 564 00:46:55,680 --> 00:46:58,840 are deflected skywards by a ridge. 565 00:47:01,280 --> 00:47:04,440 By feeling where these thermals and updrafts are, 566 00:47:04,440 --> 00:47:07,720 they can manoeuvre the wing and climb higher. 567 00:47:09,040 --> 00:47:11,200 This is what Tilly feels. This is what Tilly does. 568 00:47:11,200 --> 00:47:12,640 This is what eagles do. Uh-huh. 569 00:47:17,600 --> 00:47:21,480 One of Mike's favourite ways to find a good thermal is to watch 570 00:47:21,480 --> 00:47:23,520 and follow the local birds. 571 00:47:25,360 --> 00:47:28,160 Got another bird on this ridge here that we can try to join. 572 00:47:30,200 --> 00:47:32,240 Mike can tell how strong a thermal is 573 00:47:32,240 --> 00:47:34,640 by seeing how quickly the birds climb. 574 00:47:36,120 --> 00:47:40,680 And it's not long before he spots a familiar species. 575 00:47:40,680 --> 00:47:43,400 Look out, at the end of the ridge. 576 00:47:43,400 --> 00:47:44,760 You see the birds? 577 00:47:44,760 --> 00:47:46,440 At the end of the ridge, end of the ridge... 578 00:47:46,440 --> 00:47:48,320 Straight out, straight out, straight out. 579 00:47:48,320 --> 00:47:50,520 Straight out. Gotcha! Yeah, yeah, yeah. 580 00:47:51,760 --> 00:47:53,600 That's a goldie. Yeah? 581 00:47:53,600 --> 00:47:55,920 That's a golden eagle. Let's go, let's go. 582 00:47:55,920 --> 00:47:58,640 We're flying with a golden eagle. 583 00:47:58,640 --> 00:47:59,680 Wow! 584 00:48:04,120 --> 00:48:06,400 I've waited my whole life for this, Mike. 585 00:48:06,400 --> 00:48:08,280 THEY CHUCKLE 586 00:48:26,240 --> 00:48:30,280 This is the thing that I've dreamt about since I was a boy. 587 00:48:33,240 --> 00:48:37,840 And my whole life, I've experienced it through my birds. Uh-huh? 588 00:48:37,840 --> 00:48:40,520 But now I'm experiencing it for myself, for real, with you, 589 00:48:40,520 --> 00:48:43,760 and this is just... I can't put that into words. 590 00:48:43,760 --> 00:48:48,480 It's really quite moving, I would say. It's quite emotional. 591 00:48:48,480 --> 00:48:51,280 It's OK, you can cry. I've cried. 592 00:48:51,280 --> 00:48:53,880 I feel quite... I feel very emotional, actually. 593 00:48:58,160 --> 00:48:59,640 This is something, Mike, 594 00:48:59,640 --> 00:49:02,440 I'm never going to forget for the rest of my life. 595 00:49:05,080 --> 00:49:09,760 For Lloyd, soaring on the air currents is pure joy. 596 00:49:11,760 --> 00:49:16,040 But for eagles, it's a critical component of their daily lives. 597 00:49:18,880 --> 00:49:22,400 To be a dominant predator of the sky, they must harness 598 00:49:22,400 --> 00:49:25,200 the wind to cover their territory, 599 00:49:25,200 --> 00:49:27,400 and they make it look easy. 600 00:49:36,760 --> 00:49:40,240 To find out the science behind this superpower, 601 00:49:40,240 --> 00:49:42,840 Lloyd wants to put Tilly to the test. 602 00:49:46,520 --> 00:49:50,560 He's fitting her with a highly accurate GPS tracker to measure 603 00:49:50,560 --> 00:49:53,200 how fast she can gain altitude, 604 00:49:53,200 --> 00:49:54,960 and a 360-degree camera 605 00:49:54,960 --> 00:49:58,880 to see exactly how her wings are adapted to soaring. 606 00:50:01,160 --> 00:50:04,400 We'll know exactly... what you get up to. 607 00:50:04,400 --> 00:50:05,760 Eh? 608 00:50:05,760 --> 00:50:07,760 You're a good girl, yes. 609 00:50:07,760 --> 00:50:08,920 Bop-bop-bop! 610 00:50:10,800 --> 00:50:12,720 Go on, off you go. 611 00:50:12,720 --> 00:50:13,720 Go on. 612 00:50:17,800 --> 00:50:22,240 Tilly soon finds an updraft, and soars high above the glen. 613 00:50:23,840 --> 00:50:25,480 Woohoo-hoo! 614 00:50:25,480 --> 00:50:28,560 You make it look so easy. Eh? 615 00:50:30,600 --> 00:50:33,400 The onboard camera provides a wonderful opportunity 616 00:50:33,400 --> 00:50:36,800 to see the world from an eagle's perspective. 617 00:51:12,920 --> 00:51:16,480 Throughout the flight, the GPS tracker and accelerometer 618 00:51:16,480 --> 00:51:19,320 on her back are collecting important information. 619 00:51:28,200 --> 00:51:30,120 Good girl. Clever eagle! 620 00:51:37,360 --> 00:51:40,920 And Professor Jim Usherwood, a locomotion specialist, 621 00:51:40,920 --> 00:51:43,600 can help interpret the findings. 622 00:51:43,600 --> 00:51:45,320 Well, it's really exciting, especially 623 00:51:45,320 --> 00:51:46,880 having the video next to it. 624 00:51:46,880 --> 00:51:49,640 You can really see what's happening all the way through. 625 00:51:49,640 --> 00:51:52,960 You can see her climbing, circling seven times, 626 00:51:52,960 --> 00:51:56,600 and then reaching quite a height, really very quickly. 627 00:51:56,600 --> 00:52:00,160 She's doing, oh... three, four, five metres a second up 628 00:52:00,160 --> 00:52:01,960 and that's fast. Wow. 629 00:52:01,960 --> 00:52:04,960 That's eight, nine, ten miles per hour...up. 630 00:52:04,960 --> 00:52:06,680 Imagine running up a ladder that fast. 631 00:52:06,680 --> 00:52:08,320 So she's climbing quickly. 632 00:52:08,320 --> 00:52:11,280 Really fast, while hardly travelling across the ground at all. 633 00:52:12,800 --> 00:52:15,400 Tilly climbs without flapping her wings, 634 00:52:15,400 --> 00:52:17,440 saving huge amounts of energy. 635 00:52:21,320 --> 00:52:24,320 Eagles are able to ride the air currents effectively 636 00:52:24,320 --> 00:52:26,800 thanks to their large wing area, 637 00:52:26,800 --> 00:52:28,880 but the shape of their wing 638 00:52:28,880 --> 00:52:31,640 is different to that of many soaring specialists. 639 00:52:38,160 --> 00:52:42,040 Albatross have very long, narrow wings, 640 00:52:42,040 --> 00:52:46,200 which generate a lot of lift for relatively small amounts of drag. 641 00:52:46,200 --> 00:52:47,840 CAWING 642 00:52:49,720 --> 00:52:53,160 It makes them brilliant at gliding, 643 00:52:53,160 --> 00:52:55,600 but this wing shape is no good to eagles. 644 00:52:58,160 --> 00:53:01,320 Long wings are very good for gliding and soaring, 645 00:53:01,320 --> 00:53:03,520 but they're horrible for flapping. 646 00:53:03,520 --> 00:53:06,280 And, of course, this thing at some point will need to flap. 647 00:53:06,280 --> 00:53:08,400 Yeah. She'll need to flap to take off, 648 00:53:08,400 --> 00:53:10,080 carry the weaponry to kill something 649 00:53:10,080 --> 00:53:12,200 and then carry that food back home, 650 00:53:12,200 --> 00:53:14,520 at which point you don't actually want super long wings. 651 00:53:16,360 --> 00:53:19,200 Eagles have to deal with some conflicting tasks. 652 00:53:22,440 --> 00:53:25,200 To soar well, it's best to be lightweight 653 00:53:25,200 --> 00:53:27,080 with extremely long wings. 654 00:53:29,120 --> 00:53:31,160 But to hunt large prey, 655 00:53:31,160 --> 00:53:33,840 it's important to be powerful and heavy 656 00:53:33,840 --> 00:53:38,880 with shorter, broad wings that can flap and take off with big loads. 657 00:53:41,840 --> 00:53:45,840 Eagles manage to achieve both, but how? 658 00:53:49,240 --> 00:53:52,080 The secret is at the end of their wings. 659 00:53:54,520 --> 00:53:58,160 From the onboard camera, it's clear that the feathers on her wing tips 660 00:53:58,160 --> 00:54:00,240 are separated when she flies. 661 00:54:03,880 --> 00:54:08,360 Each one of these primary feathers acts like a tiny aerofoil, 662 00:54:08,360 --> 00:54:11,040 helping air hug the upper surface of the wing. 663 00:54:14,160 --> 00:54:18,720 It means eagles can tilt their wings at very steep angles on takeoff, 664 00:54:18,720 --> 00:54:21,560 generating lots of lift to support a heavy load. 665 00:54:26,640 --> 00:54:30,080 It's also thought these slotted wing tips can reduce elements 666 00:54:30,080 --> 00:54:33,840 of drag, helping them soar with greater efficiency. 667 00:54:38,760 --> 00:54:44,480 It's a clever solution for a wing that has to perform so many tasks, 668 00:54:44,480 --> 00:54:46,840 helping them harness air currents 669 00:54:46,840 --> 00:54:48,560 and dominate the skies. 670 00:54:55,480 --> 00:54:58,440 In Iowa, the nest is still empty. 671 00:55:01,080 --> 00:55:05,240 The parents did all they could to raise their two chicks 672 00:55:05,240 --> 00:55:08,560 and, hopefully, they will breed again next year. 673 00:55:12,520 --> 00:55:15,360 But this isn't the end of the story. 674 00:55:15,360 --> 00:55:19,160 Remarkably, both chicks have been found alive. 675 00:55:32,040 --> 00:55:35,880 The eldest was discovered washed up along the river, five days 676 00:55:35,880 --> 00:55:37,920 after it fell from the nest. 677 00:55:42,800 --> 00:55:45,360 It was later found to have a broken leg. 678 00:55:48,000 --> 00:55:51,880 The other was picked up by local residents, 679 00:55:51,880 --> 00:55:54,200 covered in blackfly bites. 680 00:55:58,040 --> 00:55:59,640 Both chicks were taken 681 00:55:59,640 --> 00:56:03,200 to a raptor rehabilitation centre for treatment, 682 00:56:03,200 --> 00:56:05,720 where they started feeding and putting on weight. 683 00:56:10,000 --> 00:56:13,280 Due to its leg fracture, it's unlikely the eldest chick 684 00:56:13,280 --> 00:56:16,320 will be released, but its future is still bright. 685 00:56:18,520 --> 00:56:21,600 Hopefully it will become an ambassador eagle 686 00:56:21,600 --> 00:56:25,240 to help inspire a new generation of eagle conservationists. 687 00:56:29,520 --> 00:56:32,160 The second chick is making a good recovery 688 00:56:32,160 --> 00:56:35,000 and developing powerful flight muscles. 689 00:56:36,400 --> 00:56:38,640 Paired up with other rescued chicks, 690 00:56:38,640 --> 00:56:42,280 it will soon be strong enough to be released back into the wild. 691 00:56:47,000 --> 00:56:51,640 It's an extraordinary end to a dramatic season, 692 00:56:51,640 --> 00:56:54,280 and a new start to this eagle's life. 693 00:57:02,120 --> 00:57:05,080 By following the journey from egg to eaglet, 694 00:57:05,080 --> 00:57:07,760 we've seen what challenges an eagle must face 695 00:57:07,760 --> 00:57:09,520 to survive its first year. 696 00:57:13,160 --> 00:57:16,000 We've witnessed remarkable dedication 697 00:57:16,000 --> 00:57:18,080 and skill from the parents. 698 00:57:21,560 --> 00:57:25,160 And thanks to a very special eagle called Tilly, 699 00:57:25,160 --> 00:57:29,680 we've uncovered the science behind their superpowers. 700 00:57:29,680 --> 00:57:32,000 I'm so proud of her because, 701 00:57:32,000 --> 00:57:35,160 in her own way, she's brought 702 00:57:35,160 --> 00:57:38,360 much more knowledge and understanding to an eagle's world 703 00:57:38,360 --> 00:57:40,400 about their incredible eyesight... 704 00:57:40,400 --> 00:57:43,280 She's coming in fast! Woohoo! 705 00:57:43,280 --> 00:57:46,040 ..that amazing ability to use the air 706 00:57:46,040 --> 00:57:48,920 to soar so well, 707 00:57:48,920 --> 00:57:50,720 and her hunting strategy, 708 00:57:50,720 --> 00:57:53,360 and the power in those feet! 709 00:57:53,360 --> 00:57:55,440 Bring all those things together 710 00:57:55,440 --> 00:57:58,880 and you've got the best aerial predators on the planet. 711 00:57:58,880 --> 00:58:01,480 They really are incredible. 712 00:58:01,480 --> 00:58:04,480 Eagles have long captured our imagination. 713 00:58:05,640 --> 00:58:07,840 Their combination of strength, 714 00:58:07,840 --> 00:58:09,440 elegance, 715 00:58:09,440 --> 00:58:11,280 and skill 716 00:58:11,280 --> 00:58:13,160 make them appear almost... 717 00:58:15,160 --> 00:58:16,760 ..superpowered.