Watching reed warblers: from skilful nest builds to chicks' first flights

Reed warblers are small, brown birds known for their noisy, rhythmic song. But what they lack in glamour, these tiny migrant birds make up for in ingenuity and skill.

I watched a pair as they built their incredible sling-like nests, laid their eggs and helped their tiny chicks make their first shaky flights. 

Bird watching beside a lake

I spent much of spring up to my ankles in freezing cold water filming a mute swan nest. But as much as I was mesmerised by the swan family, it was a much smaller, plainer bird nesting nearby that made my bird watching days go by quicker.

Reed warblers' spring migration

Reed warblers migrate to the UK each spring from Africa, arriving in their numbers to breed beside our lakes, rivers and waterways. From my swan hide, hidden deep in a reed bed on the edge of an East Yorkshire lake, I watched as over the period of a week more and more birds arrived.

By the end of April I counted 20, their loud, incessant song ringing out across the lake from dawn to dusk. They arrived just as the first green shoots began to appear, slowly brightening the winter-brown reed bed. It was as though this colourful injection of new growth was what they had been waiting for.

Reed warbler's skillful nest builds

And sure enough, as soon as the warbler pairs arrived, they quickly got to work building their nests amongst the growing stalks. I watched as the pair closest to me set about constructing a nest. The size of a small teacup and woven from grasses and fronds left over from previous reed seed heads, it was fascinating to see how it was made.

Slung between three or four reed stalks, and woven into place just above a leaf node, it hung, suspended three to four feet off the water with just the stub of a leaf bud to stop it from sliding down the shaft of a reed. Sometimes, when the wind pushed the stalks apart, these persistent birds had to begin their build all over again, this time tying the stalks more tightly together to prevent further slippage.
Fascinated I waded through the reed beds looking for more warbler nests. I found six in just one evening.

Cuckoo threat

Back at the first nest, I was just settling down to watch when I heard a male cuckoo calling, it’s distinctive call coming from a nearby willow tree. Reed warblers are among several British species this parasitic bird tricks into raising its chicks and I wondered if the nest I was watching might become prey to a cuckoo imposter.

Some 30 years ago I had filmed this fascinating process in a reed warbler nest in this very spot, but despite checking warbler nests for years afterwards I haven’t seen cuckoos in a reed warbler nest here since.

Egg-laying & incubation

By May, the female warbler had laid its first egg. Pale green with a splattering of olive-coloured blotches across it, it and looked quite beautiful in the grass-lined nest. The egg was soon joined by a second and then a third as the female laid one egg a day until there was a clutch of four.

She began to incubate the clutch after the third egg was laid and after just 12 days the first chick hatched out. It was incredible to be able to film the moment so soon after watching the egg laying and to capture the tiny hatchling swallow down its first feed within hours of emerging from its eggshell.

Tiny, dark chicks hatch

Reed warbler chicks are surprisingly dark in colour and have no downy feathers to protect their tiny bodies from the cold. The adult female kept it warm beneath her all that day, only changing places with the male momentarily when she needed to stretch her wings. After almost eight hours of waiting for the second chick to hatch, I noticed the female warbler become restless. As she shifted position, I spotted a small pip in the egg and then, during a brief changeover between male and female, spotted a large crack around the circumference of the egg.

Although the female did most of the incubation, during their occasional swaps I could see the chick slowly emerge. I saw it arch its back to prise the eggshell open. Then this minute chick was out and lying exhausted on the floor of the nest.

Nest maintenance

The female warbler quickly settled down on it to brood, but she seemed uncomfortable and kept pecking down into the nest. After about half an hour of fidgeting, she began removing eggshells from beneath her, one half at a time, and flying off with them in her beak. It is quite common for birds to remove eggshells so as not to attract attention to their nest, so I assumed she was dropping them a good distance away.

I continued filming as the third and then, just before nightfall, fourth chick hatched. It was raining as I packed up to go home and my legs were numb and stiff with cold. I had been sitting in my hide for 12 hours wearing rubbery chest waders and couldn’t wait to take them off!

Male & female parenting roles

The next day I was back at the nest early to continue filming. Now the warblers were taking it in turns to feed their chicks. The weather was unseasonably cold and once when the male arrived ready to take his turn on the chicks, the female refused to leave the warmth of the nest. With my own feet dangling in three feet of water, I knew just how she felt.

The male had little option but to fly back out to find more insects. When he returned, I watched her snatch the beak full of insects from him and then rock back to feed the tiny chicks beneath her. As she did so the nest lit up with the bright red, open gapes of all four chicks, all begging to be fed. At the back of each wide-open beak, I noticed black spots. I presumed these were target marks on their tongues to guide the adults’ deliveries.

The male returned trip after trip; his beak crammed with food. It was fascinating to see how attentive both birds were in making sure each insect was delivered into the gaping mouths below.

Warbler chicks grow fast

With so much food coming, the chicks were developing quickly and so, keen not to miss anything, I visited the nest every other day. During this time the warblers grew so used to me being there they would sometimes fly through the camouflage netting surrounding my cameras and as they passed, I could feel the breeze of their wings.

Each time I returned to the nest I was surprised at how much the chicks had grown. During the first few days the chicks were so small it wasn’t possible to see them from the side of the nest and I was restricted to views via my camera monitors. But then on the fourth day as an adult came to feed, I could suddenly see all four heads peeping over the rim of the nest, their beaks wide open and pointing skyward as they begged for food.

As the chicks got bigger, this became quite funny watch. Any hint of a warbler hopping through the reeds and the chicks suddenly sprang to life, all four beaks opening wide in unison. If the sound turned out to be a false alarm, they would just as suddenly hunker down so as not to attract attention from predators.
Sometimes the adults delivered insects that were too large, like damsel flies. Watching them offer one to each chick in turn, I wondered if they were testing their development.

Feathers develop

At five days old the chicks started growing pin feathers and their little bodies filled the nest with the silvery sheen of these tiny protective feather casings. Now the chicks’ appetite seemed never ending. With each food delivery the chicks competed for attention, trying to be the one to snatch the food first or to beg the loudest.

At nine days their feathers began growing through and on the 11th day as I headed down to the nest, I noticed two of the chicks had already fledged.

Fledging chicks

It didn’t take me long to find the fledglings hopping through the reeds, but it was hard to keep track of them in the dense beds. I quickly set up my cameras to film the last two fledglings. I had to wait slightly longer than usual for an adult to arrive and assumed this was because they were also feeding the first two fledglings in the reed bed.

Interestingly the chicks in the nest would spot their older siblings and react with loud cheeps, clearly mistaking them for the adult. There was more space in the nest now and the remaining two began hopping up on to the rim of the nest flapping their wings vigorously.

The adults were delivering food quite sporadically and often arrived with no food at all. Many birds will withhold food to encourage chicks to fledge and just as I was just wondering if this was the case, one of the chicks hopped out of the nest.
I quickly began focussing my camera, but there was no time and so I gave up and watched instead as the chick grasped onto a reed and then almost bounced onto another stalk.

It was so small it looked more like a large insect than a bird as it hopped from stem to stem. In this odd, halting way, the chick made its way back to the nest, which was a relief to me as I hadn’t managed to film the moment. Little did I know then that both chicks would go on to do this over and over and I had plenty of further opportunities to film these short adventures.

Staggered first flights

As the evening started to close in, it began to rain again and the two chicks huddled into the nest, their heads tucked under their wings. I left on the cusp of dark and returned early the next morning to find the nest empty and one of the chicks sitting on the base of my hide, its short tail dangling in the water.
The bedraggled chick scrambled up through the reeds and before long had climbed six feet above water level. It looked thoroughly miserable and soon closed its eyes – I assume it had been a tough night for this little warbler.

Nearby, I could hear the other three chicks calling for food. It was a continuous noise, different to the intermittent cheeps they made when they were still in the nest. As the first chick started to dry out, I heard it join in the calling, its wings quivering as it also begged for food.

Last moments with the warblers

Eventually an adult heard the calls and arrived with a beak full of insects. This chick climbed up to the top of a reed, way above the nest it was brought up in, and then took a short flight back down into the reed bed where it was fed by an adult again.

I stayed with the warblers for the rest of the morning, but it soon became challenging to get glimpses of them. As I began removing my cameras from their nest, I reflected on the incredible insight I’d had into their secret, eventful lives.
And although it had been fascinating, the experience only recharged my original wish to again watch these warblers cope with the added challenge of raising a cuckoo imposter in their nest.

So, before the breeding season was over I decided to do one more round of the reed beds to see if I could find a cuckoo chick lurking in one of the warbler nests.

Have you spotted a reed warbler nest in your area? Share your experiences in the comments, or subscribe to my newsletter for more birdwatching insights!