Raising a cuckoo chick takes reed warblers twice as much time and a LOT more effort than bringing up four chicks of their own. In the final chapter of this story, I discover how, even when heavy rain pushes them to their limits, reed warbler foster parents never give up on their cuckoo chick imposter.
*ABOUT ME* ____________
I am a British wildlife artist and filmmaker on a mission to share my love for wildlife with the world. As well as creating detailed animal film and art portraits, I promote wildlife tours around the world and do all I can to help conserve and protect wildlife here at my home in Yorkshire. I hope that by putting nature in the frame I can foster a deep love for wildlife amongst my followers.
You may like to purchase my artwork: https://www.robertefuller.com. Many of my paintings are portraits of the characters you watch here!
Cuckoos v reed warblers Cuckoo chicks rely on a host species to raise them. I found one after searching 15 reed warbler nests and I documented every moment as a pair of reed warblers raised it. Meanwhile I also followed a reed warbler nest where a pair were raising four of their own kind, recording the behavioural differences between the two sets of bird parents.
Different diets for different bird species In the reed warbler nest, feeding four mouths was no easy feat. At four days old the chicks seem to be constantly hungry. Interestingly the parents delivered small insects, appropriate for their small-sized beaks. Meanwhile the cuckoo's foster parents were also hard at work, in this case bringing in larger insects like damselflies and even bumblebees - as though each menu had been carefully tailored to suit each chick.
Cuckoo call change The chicks in both nests call out for their parents to feed them whenever there's any movement nearby. But at about 16 days old the cuckoo chick began to make a different sort of call. The sound, a 'cheeping' was intended to help the reed warblers locate it once it has left the nest. Once they arrived, the chick returns to its original 'begging' call.
Brooding chicks The reed warbler chicks grow quickly and the female soon struggled to brood them all. When they are genuinely too big to brood she switched to sitting at the side of the nest. Meanwhile the cuckoo chick threatened to outgrow its nest at just one week old and by 16 days you could barely see the nest beneath it.
Chick feather development Once they were no longer being brooded, the reed warblers begin to quickly grow their feathers, and over the course of just two days the difference was palpable - which was just as well because when bad weather hit they became vulnerable to cold.
Rescuing a reed warbler chick In the end the storm didn't affect the brood of four, or the cuckoo chick, but another reed warbler nest in the reed bed collapsed and a tiny chick had fallen. I waited to see if the parent birds fed it where it was and when the chick seemed too cold to respond I picked it up and warmed it in my hands before putting it back in the nest.
Chicks fledge At 11 days old, the reed warbler chicks fledged, making their way up through the reeds. But at this stage these young birds became very vulnerable and I watched kestrels circle overhead with concern. Thankfully the chicks survived and it was great to watch them practise their techniques. In a few weeks time these birds would make their long migrations back to Africa. In contrast, the cuckoo left the nest at 18 days but it was by no means able to fly and thankfully landed in an old moorhen nest and not in the water below. As the cuckoo continued to gain confidence, the reed warblers continued to feed it, sometimes having to perch on its back to reach this giant chick!
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Credits: Edit: Sam Kite, Oliver Riley-Smith. Camera: Robert E Fuller. Additional Cameras: Sam Kite, Gary Lawson, Will Mercer. Drone: Robert E Fuller
Not only does this single cuckoo demand more food than a whole brood of reed warblers,
it takes almost double their time to raise. Cuckoo chicks hatch in a nest that's not their own.
This one is being brought up by reed warblers. I searched in the reed beds for weeks to find it.
I had found 14 reed warbler nests. It was the 15th that proved most fruitful. I found a cuckoo chick.
Then I began to document this extraordinary journey of being raised from a young chick,
then ready to take its first flights by parents that don't know it's not their own.
I built two hides, one to study reed warblers with their own chicks
and the other to study their nest with the cuckoo chick in.
I've already caught some very rare behaviour, like this reed warbler regurgitating a pellet.
Join me as I follow these two nests through their final chapter, when some heavy rain
pushes these reed warblers to their limits. I intervene when a reed warbler nest almost
collapses and the magical moment after all of the warbler's hard work, the cuckoo fledges the nest.
I've been watching this cuckoo a week now and it's incredible to see just how much it's grown.
Having watched warblers bring up their own chicks, it certainly looks like it takes more food to
bring up a single cuckoo. But feeding four males is still no easy feat. The chicks are so ready
for food they're calling out whenever there's any movement. Sadly for them it's just the wind
But the adults are never far away, returning with food soon.
These reed warbler chicks are now four days old. The female is still brooding them and the male
is busy hunting. But these chicks are growing fast and are hungry, so the female joins the male
in hunting for food. Cuckoos choose hosts with a soft insect diet. These reed warblers are kept busy
I've noticed that reed warblers are bringing in larger insects to feed this bigger cuckoo chick.
Damselflies and even bumblebees are on the menu. In the other nest the reed warblers
are bringing in smaller insects to feed their brood. And what goes in must come out. Fecal
sacs are either taken away or eaten. In the early days anyway the nutritional value decreases as
time passes, due to the digestive tracts of the chicks developing. But these chicks grow quickly
and the female struggles to brood them all. And will spend more and more time hunting to feed
these chicks. As the days go by brooding becomes even more difficult. The chicks are growing fast
and you can see the feathers breaking through the pins. And over the course of two days the
development is huge. Looking back from day one to day nine the growth is extraordinary.
The warbler chick's now nine days old and it's astonishing to think they could fledge in just
three days. But unfortunately some bad weather soon hits. This weather could spell disaster
for the lightweight reed warbler nests. After all of the wind and storms recently I'm really
worried about the warbler nests because they're so fragile suspended in these reeds. So I've just
checked nest two which is the one I'm filming and everything's okay in there. So I'm just going to
head on now and see how that cuckoo chick's getting on. So the nest with the cuckoo chicken is just
through here. Oh yeah look at that it's still in the nest down there which is great news. But I'm
going to go now and check all of the other warbler nests just to see how they're getting on.
So I've just checked nest three and everything's good in there so I'm going to head up and see how
nest four's getting on. So nest four's through here and it actually looks like it's collapsed.
Oh there's a little chick down here and that's too young to be out of the nest and it's looking
pretty cold. But I'm just going to wait here and actually just see what happens see if the adults
come to feed it. The adults are coming through the reeds and they've got some food. Oh look at this
adults are trying to feed it but that chick's too weak and cold to feed. Oh it's so sad to
see this. So there's no sign of any of the other chicks at the moment and I think they must have
perished now. But I've just got to work out what to do with this little chick because if it's not
feeding this is going to die as well. So I think I'm going to have to head in there and actually
catch it warm it up and try and get it back in that nest. Right I've just had that little chick
in my hands warming it up and I've got it back in the nest. Oh the parents are back already.
Oh look at that they're feeding it. Oh superb. Hopefully all the storms have passed now and the
rest of those warbler chicks fledge safely. It's now time to get back to filming starting with the
reed warblers. I'm just setting up but I think there's only two chicks left in the nest.
I can hear the fledglings calling in the reed bed and there's definitely just two left in the nest.
Reed warbler chicks can fledge in as little as 11 days. In contrast at 11 days old cuckoo
chicks are still about a week from fledging with a lot of pin feathers still visible.
Oh look at this one it's just fledged. It's the first time this chick's been alone in the nest
and just listen to it calling out. All that calling's paid off. The male's just arrived to
feed it. It's not going to be alone long. One of the fledglings is just coming back through the reeds.
It's just scrambled back into the nest. Oh it's off again. It keeps taking little adventures
into the reeds. Oh look at that they've settled in for the night. I think I'm going to leave
them to it now and I'll return in the morning. I'm back at the reed bed to see how the fledglings
are getting on and I think I've spotted one just there. It's been raining overnight and that one's
still a little bit damp but the weather looks quite fine now so that one will soon dry off.
Oh that's nice it's having a little preen now. It's on the move making its way up through the
reeds so that's one of the chicks accounted for. Back in here all the others calling in the reed
bed lower down. It's such a challenge getting a clear view of these chicks. I'll put this one
headed up to the top of the reeds there. Oh that's incredible. It's made its way right to the top.
I really worry about them at this stage. Sat up there they could easily be picked off by predators
such as corvids or kestrels. But there's so much thick cover in this reed bed I'm sure they're
going to be fine now. These chicks look so vulnerable at this age but in a few weeks time
they're going to be flying as well as their parents and it's incredible to think they're
going to then make that long migration all the way to Africa. And just like that there's another
successful brood for these reed warblers. But over at the cuckoo nest there's a big development
change. The cuckoo's actually sat up on the rim of the nest it won't be long before it leaves now.
When I first found it it was a week after hatching but now it's about 16 days old.
So today the cuckoo chick started making a different call and that's in preparation for
fledging. So once the cuckoo leaves the nest this cheeping sound will help the reed warblers locate
it to give it even more food. But as it's being fed it returns to the original begging call.
Fledging is a really difficult time for any cuckoo chick but especially for those ones
growing up in the reed warbler nest. The fragile nest of the reed warbler isn't designed for a
heavy weight of a cuckoo chick. You can barely see the nest underneath it and quite often in
windy weather these nests will actually collapse and the cuckoo chicks end up in the water.
I've been watching this cuckoo chick grow for the last 10 days and I've got quite attached to it.
So I hope this one fledges successfully.
The cuckoo chick could fledge today so I can't wait to see how it's getting on.
I can hear the cuckoo chick calling. I wonder if it's still in the nest?
Well the nest is empty so the cuckoo is out and about.
Well look at that it's just down here. It's actually in a moorhen nest.
So that's been really lucky for the cuckoo. It's not fallen in the water. I'm just going
to get my camera set up on that. It's absolutely amazing. This cuckoo chick has fledged 18 days old
a whole week later than the first reed warbler chicks. That cuckoo chick has literally been
given a lifeline by this moorhen nest. But sat down here it would make an easy meal for a passing
otter or mink. The cuckoo is calling out for food and look at that the reed warbler is coming in to
feed it. The cuckoo chick's just pecked out of the warbler again. It's clearly hungry. Even with a
beak full of food this cuckoo is constantly calling for more. It must have fledged earlier
this morning and I use the word fledged very loosely. It's more or less just flopped out of
the nest and I don't think it'll be able to fly yet. Oh it's on the move. It's making its way up
through the reeds. The cuckoo chick's only made it a few meters away from the moorhen nest
and it's just down here waiting to be fed. But the adults know exactly where it is and are busy
delivering food. It's pecked out again. It's great to see it perched on a branch. It's definitely
growing in confidence. It looks a bit more steadier on its feet rather than scrambling
around in the reeds. While this cuckoo chick's over the water I'm still worried about it
but hopefully I'll make it over onto this island onto some drier land.
This is the third day the cuckoo chick's been out of the nest and it's made it onto the island.
The cuckoo chick is as hungry as ever demanding more food
and it works but the wobbler seems more wary standing a bit further away
and then on a different branch entirely.
It's been great following this cuckoo chick for the last two weeks
and just look at it now. It's taken its first flights but it's not made it far.
And the wobblers are still feeding it up there. So it's calling continuously for food now and the
wobblers are able to find it no matter where it goes. Oh it's flying up through the trees now
getting higher and higher. So this cuckoo chick's on its way to independence
but these wobblers are going to feed it for a few more weeks first before it heads off to Africa.
But it's not just the reed wobblers that might hear the vulnerable hungry cuckoo chick
and I worry with all this noise it might attract the wrong attention.
There's a sparrowhawk nesting nearby with very hungry chicks and I often see buzzards
soaring overhead catching the thermals on a lookout for a meal. So I can hear thunder rumbling
in the distance so there's a storm on the way. This is going to be the first big test for this
young cuckoo. Cuckoos have soft feathers so this chick could quickly become exhausted
losing critical energy if the feathers become waterlogged. Thankfully the rain was short-lived
and the sun soon returns and the cuckoo chick dries off. Not only does this single cuckoo
demand more food than a whole brood of reed wobblers it takes almost double their time to
raise, taking a lot more effort from the reed wobblers.
But it won't be long now before this young cuckoo sets off on its 5,000 mile journey to Africa.
Reed wobblers can raise two broods in a normal breeding season.
For the wobblers that have raised a cuckoo chick it's unlikely they'll have a second brood that
year. Over 30 years ago when I first found that cuckoo I couldn't have even imagined having all
these different cameras to film every angle of this amazing spectacle. It's been amazing to
watch the curious relationship between these two species. Despite everything those wobblers
have looked after it as if it was their own.
