TRICKED! This Giant Cuckoo Chick Isn't Theirs | Reed Warbler & Cuckoo Part 2 | Robert E Fuller

I had found 14 reed warbler nests. It was the 15th that proved most fruitful. Oh look at that, I've actually found a cuckoo chick. It's been over 30 years since I've seen this, a little cuckoo in a reed warbler's nest. Can't wait to get my cameras on this. Everyone knows the story about cuckoos laying their eggs in other birds' nests, but seeing it playing out in real life is quite incredible. Previously I made it my mission to follow the breeding cycle of reed warblers in the hope to find a cuckoo chick. So far I've found 14 nests and I'm going to keep my eye on all of them. Now I'm catching up with the reed warblers whose eggs are about to hatch. There she is. Look at that, she's looking at the eggs. It looks like she's almost counting them. And there, that's wonderful. She's settling in to brood those eggs. Yesterday she was hopping straight onto the nest, but look at her now, she's really inspecting her eggs. She can probably hear the chicks tapping from inside. Oh look at that, the male's on his way. And he's brought a bit of food for the female, but she's headed straight off the nest. So I think he's going to go to brood in. I love it when they shuffle down onto the eggs. And I can see him just right through here. But there's a slight reaction there, I can hear the female coming I think. Yeah, he's off. So the female must be on her way. Oh yeah, she's there. Again, she's checking the eggs and taking over brooding. So she does the majority of the brooding, especially at night. But he comes and takes over for little stints, relieving her. But this time he just comes in to feed her. It's only been 12 days since the warbler started incubating, and amazingly they could actually hatch tomorrow. So I've just got set up and one of the chicks has hatched already. I've just got to wait for the next one now. This is fascinating, the warbler's testing the strength of that newly hatched chick. They've got to be strong if they're going to survive the cold spring. The female's getting more fidgety, checking the eggs. I think another one's going to hatch soon. The female's just left. Oh, and look at that, the second egg's hatching. The chick's actually prizing itself out of the shell. That's just amazing. She's just taken the eggshell out. She's taken it through the reeds. She'll drop that far away from the nest, so she doesn't attract attention to her newly hatched chicks. The second chick's only a few hours old, and it's just had its first feed. It's taken over two days for them all to hatch, but we've now got four healthy chicks in that nest. With plentiful insects coming in, they're going to grow quickly. She stays on the nest brooding while he delivers her the food, and then she's feeding the chicks underneath her. It's absolutely magical to watch. Although I've found 14 reed warbler nests, my mission is to find a cuckoo chick being raised. So day after day, my search continues. Oh, there's another warbler nest just through here, and this is a new one. I haven't got my camera with me, so I'll just check inside the nest. I can't see into the nest at the moment. Oh, look at that. I've actually found a cuckoo chick. It's been over 30 years since I've seen this, a little cuckoo in a reed warbler's nest. Can't wait to get my cameras on this. So that evening, I build a hide on this new nest where the cuckoo chick is. There we go, the hide's complete. So it's just in case I'm leaving it open now at 10 in the morning with the cameras. I can see right through to where I don't have to listen. Brilliant. Cuckoo chicks will push out the host eggs or chicks to remove competition. So when I filmed the cuckoo 30 years ago, I had one Hi8 camera and things have moved on a lot since then, and it's going to take me a few trips to take all this equipment in. So the nest is about 50 meters away down this channel. The swans have made this channel to access their nest just behind me, but it makes a really easy way for me to get around. Right, I can't wait to get this camera equipment set up and the reed warblers in there feeding the cuckoo chick. With me actually stood here, that's absolutely amazing. Right, I'll get it set up. Now that's a slight alarm call. I need to stay really still. I now have two hides set up, so I can film the reed warblers and the cuckoo chick in tandem and watch their fascinating progression through to fledging. With two nests to film, I spend my morning with the reed warblers and the afternoon filming the cuckoo's development. Right, I've got the cameras rolling. So this cuckoo chick's only about a week old and it's already filling a nest. Cuckoos are parasitic birds, laying their eggs in host species nests like these reed warblers. These chicks are raised by the unsuspecting host species. The cuckoo's duty is over after egg laying and has no part in incubation or raising the chick. I found 15 reed warbler nests this year and thankfully the cuckoo laid its egg in the strongest looking one. That was amazing, both warblers came in to feed the cuckoo and they didn't take any notice of me or the hide. The warblers sometimes look amused by this huge chick but they're still raising it as if it's their own. The reed warbler chicks are now four days old and the female's just there brooding them. The male's here with a beak full of insects. This time he's feeding the chicks. As these chicks grow, the female's spending more time catching insects too. Reed warbler chicks have black dots on their tongues. These are thought to act like targets when the adults are delivering food. Back over at the cuckoo nest, one of the adults has just come in to feed the chick and it's incredible to see how red the gape is as it opens its beak. Just listen to that cuckoo calling. That's designed to sound like a whole brood of warbler chicks and it's doing the job because it's encouraging these warblers to bring more food. Both parents have arrived now and they're literally bringing in food every few minutes. It's just incredible to watch. The parents have really got the work cut out here because this chick will actually eat more than a whole brood of reed warblers. There's a warbler here now and it's brought a damselfly this time. The damselflies are really quite beautiful but for the cuckoo it's just more food. With all this food going in, it's got to go somewhere but these reed warblers like to keep the nest tidy and they carry away the fecal sack and this is incredible. The female's actually trying to brood this chick. This is really comical to watch. That cuckoo chick now is way, way bigger than the reed warblers. This is one of the most incredible relationships in the animal kingdom. The cuckoo chick requires so much upkeep that the reed warbler pair will only likely raise a single chick in a year. Cuckoo chicks take longer to raise than their own brood. Reed warbler chicks will typically fledge as young as 12 days old but cuckoo chicks take a week longer, fledging at around 19 days old. This means they're only likely to raise one single cuckoo chick as opposed to two broods of their own in the breeding season. This cuckoo chick is developing really fast and at around nine days old you can really see its feathers starting to come through now. These two reed warblers run off their feet feeding this cuckoo chick. It's constantly calling for food. Thought to compensate for the hosts only seeing one mouth to feed. That's absolutely beautiful. The cuckoo chick's bringing its feathers. The weight of this cuckoo chick is really weighing this nest down especially in this wind. When I first found this nest I tied the reeds together beneath it and if I hadn't done that this nest would have collapsed by now. Oh wow, look at that! The female is delivering food and the male arrives with more. One of the flies is still alive and tries to escape but the male immediately recaptures it and delivers it back. Everyone knows the story about cuckoos laying their eggs in other birds' nests but seeing it playing out in real life is quite incredible. This has been amazing. I had found 14 reed warbler nests. It was the 15th that proved most fruitful. I found a cuckoo chick. Oh look at that, I've actually found a cuckoo chick. It's been over 30 years since I've seen this. It's developing quickly, eating more than a full brood of reed warbler chicks. Join me next time when despite some tough weather conditions both species fledge. And I'll follow this cuckoo chick beyond the nest.