Reed Warbler – Enviro-Mentalist

Of Cuckoos and Climate Change

I was fortunate enough to tag along a guided walk with the eminent cuckoo expert and behavioural ecologist Nick Davies at Wicken Fen. During an hour and a half’s walk he imparted a wealth of information about cuckoos (and does a fantastic cuckoo call that had me and the cuckoos fooled) and their ‘hosts’ at Wicken Fen, Reed Warblers.

Reed Warblers spend their winters south of the Sahara and then travel back to Europe each spring – they come back to the same spot each year to breed – an amazing bit of navigation! The males will sing and sing until he pairs up. Then his songs become much shorter – one way to tell an unpaired male.

Reed warbler nests are beautifully woven around reed stems, the female starting off by anchoring in some spider silk and then weaving the nest around herself to make perfect fit. She lays one egg per day until she has four eggs. Unless, of course, she is spotted by a cuckoo. The cuckoo, who only lays in the afternoon, waits until the nest is unguarded, swoops down, swallows one of the reed warbler’s eggs and replaces it with her own. All in a matter of seconds. If the cuckoo has missed her chance and the eggs are all there, she will eat all of the eggs to force the reed warblers into starting a second batch, then, she will be watching and waiting for her opportunity. Each cuckoo will only parasitise the one species – at Wicken it is Reed Warblers. The cuckoo’s eggs will be a perfect match for colour and marking, but are almost imperceptibly bigger.

Once the cuckoo hatches of course it will eject the remaining eggs or chicks from the nest. The reed warblers will continue to feed their giant youngster, the colour of the gape and the pitch and sound of the cuckoo begging for food fools them into thinking they are feeding a brood, pushing them to bring more food than they would for one chick alone.

It seems as though all should be well for the cuckoo as there are reed warbler nests every 20 metres or so along the lodes (man made waterways within the fens). But, sadly it isn’t so. Cuckoos have suffered a massive decline in recent decades. Or, at least cuckoos in England have – Scottish cuckoos seem to be doing OK. Wicked has mirrored this decline. Thirty or so years ago there were about 15 female cuckoos laying in the fen, with the result that about 10% of nests were parasitised. Now, it is down to just two cuckoos, with only two or three per cent of nests parasitised. The difference between Scottish and English cuckoos’ success could all be down to climate change. The two sets of birds take different routes to their sub-Saharan wintering grounds. English cuckoos go through Spain, whereas Scottish cuckoos choose a route through the Po valley in Italy. Much of Spain has suffered severe droughts over the last few decades meaning it is more difficult for the cuckoos to feed and put on enough weight to make it over the Sahara. However, this might not be the only reason, and more answers will only be revealed as we learn more about this elusive bird. The future remains uncertain.

For more information about the cuckoo tagging project see the BTO’s website.

If you want to learn more about cuckoos, then please consider buying the excellent book, Cuckoo: Cheating by Nature, by Professor Nick Davies. It contains a wealth of information and is well worth a read.

One of the best £25 I have spent?

I went for a couple of walks last weekend, not entirely with birdwatching in mind. One was round the country park – I know now that there is both a reed warbler and a sedge warbler there at the moment. I have also realised that the sedge warbler that I thought was singing from the reeds in the Industrial Estate all these years was probably a reed warbler – or at least it is this year. And I can confirm that despite trying to confuse me by duetting with a reed bunting, there are more reed warblers around Barnes Meadow than sedge warblers and quite a lot of common whitethroats this year too.

Even better though, I found my first ever willow warbler on my local patch. I had wondered if they were there, but I just didn’t know it and they were. It was singing its little drifting down song from the top of a willow tree on the old railway track, 5 minutes from home. I even managed to pick it out with my binoculars. So a lifetime first for me – that’s four new warblers that I’ve seen this year, and one new one that I’ve heard but not seen.

Hopefully I will remember everything from my warbler ID course after a long winter when there are no warblers about to bring sunshine into the grey.

Brandon Marsh Blog part two

So, the reason why I often find myself disappointed with Brandon Marsh is because on my first visit there I was spoilt with fantastic views of kingfishers and a hobby from the Carlton Hide. I haven’t seen a hobby there since and it’s a while since I spotted a kingfisher there (I have in fact seen both of these at Daventry Country Park). The Carlton hide should offer fantastic views of waders and water birds. But it doesn’t. Last time I went the bird count was similar to that at the Teal Pool Hide – aka nothing. So I was set for disappointment when I opened the shutters (there was no one else there). But, today, my view was filled with house martins and swallows darting about in front of the hide, chasing insects over the reed beds, twittering to each other and performing aerial acrobatics.

View from the Carlton Hide

I saw another whitethroat at close range and saw my first black cap of the year – a male (I’d heard plenty, but not seen any so far). There were reed or sedge warblers about – I think sedge and I got a good view of a female reed bunting darting about in the reeds – as they do I suppose. There was a cuckoo up here too, although I still couldn’t see it and it sounded some distance away.

In the last few years they have extended the reserve, the latest addition being some screens up at Newlands, overlooking more of the reed bed. Or at least that was what was there last time, now they have a new hide!

The Ted Jury Hide

These are the views left and right through the screens:

But when I went in and opened up the shutters, oh my, what a view, it nearly took my breath away:

There was a constant burble from the house martins hunting in the reed beds in even larger numbers, but there wasn’t a lot else that I could see. Still, it is early days and these things tend to take some time to settle down. I waited a while in case an osprey turned up – after all they’d kindly erected a platform for him to land on, but not surprisingly, he didn’t show. Still there were plenty of house martins and sand martins to keep me mesmerised. I realised that the sand martins were much easier to differentiate than I thought, even at speed (theirs, not mine). They don’t have the white rump that their cousins the house martins have and they also make a very different sound, more squawky than the tweeting of the house martins. I hate to say it, but a hobby would have had good hunting round there today.

I worried about getting back before they closed the gates, but couldn’t resist going towards one of the hides and out towards a different part of the reed bed in the hope that I might find a Cettis warbler as I’ve heard them round that side most years. However, on this occasion they disappointed and I didn’t hear anything. I wandered further along and met a couple of gentlemen who were going the opposite way and told me that there was always a grasshopper warbler singing in the nearby marshy areas if I just stopped and listened. A grasshopper warbler – that would be a lifetime first for me. Although, going by my sedge / reed warbler dilemma the chances of me actually recognising it were close to zero. Still I stood and listened. And, I heard a sedge warbler or was it a reed warbler. I waited and then I heard it, very faint, but definitely, something that really did sound like a stridulating grasshopper. Amazing – what a day.

I didn’t hear it again, although I wandered along the path by the reed bed. I did hear other warblers and, some sounded less scratchy than the sedge warblers I’d been listening to and they didn’t seem to stop to start again. Hearing them side by side I am pretty sure that I did hear a reed warbler, so, although I still haven’t seen one, I have now heard one. After all, the whole point of warblers is their song.

Today was all about the birds

I have had a love-hate relationship with Brandon Marsh for many years, but whenever I am feeling at a loose end or a bit grumpy then I plan an afternoon over at the reserve. Today was one of those days as I paid a traditional holiday visit to what is really a giant reed bed with some other watery bits.

I was greeted by three swallows flitting across the entrance way, shards of summer against an leaden and cloudy sky – perhaps these were a positive portent for the afternoon. I started with a traditional stop at the Badger Tea room – no badgers and not really much cake either, so just a hot chocolate for me. The tea room was noisy but all conversations blended into a general hubbub. There were two large tables of people, I don’t think they were connected, one populated by older, mainly male visitors to the site, the other younger and with more than one token woman.

There were no birds to be seen on the feeders outside, but as only the nut feeder had any contents this was not really a surprise. I downed my hot chocolate with more speed than the £2.20 cost deserved but I was eager to go out birding. It was a bit cold and breezy, although the sun did come out at times (as did a bit of rain) so today was all about the birds and I had no expectation of seeing any insects.

At the start of my walk, the sound of the cement works pretty much drowned out everything, even the most vociferous of chiffchaffs. I was briefly distracted by what I thought was a Volcuella Bombylans (or bee mimicking hoverfly) sitting on the dragonfly ID board and doing a not very good impression of a bee, but it stayed no time at all, so I am not one hundred per cent convinced. A little further on greylag geese honked in numbers to drown out the cement works and then I heard the whisper and rustle of the wind in the just opening leaves of the tall poplars.

I headed to the main set of hides and suddenly came across a carpet of violets which was a bit of a surprise; round the corner there was a bank of primroses still in full flower. I bent down to take a photograph of a cuckoo flower and heard, just twice, cuckoo, cuckoo off in the distance. How appropriate!

Cuckoo Flower

There are still long tailed tits contact calling, a really comforting sound from what is probably my favourite bird (although on another day I might have to admit that a red kite is in fact my actual favourite).

Whilst I was looking at what were probably the holes made by some species of mining bee, it was too cold for them to venture out, I happened to look up briefly and got a cracking view of a whitethroat in the tree in front – my first for the year. It then darted off into some nearby scrub, but started singing at me. I also heard a sedge warbler.

Mining Bee Holes?

The first proper stop that I made was at the Teal Pool Hide. I usually wander in just in case there’s something interesting on the pool outside the windows, and every time I usually find that there are actually no birds at all, not even dull ones. Today there was a family of mallard; mum and ten or eleven chicks. I should have been able to count them, but they kept zooming and careening about.

View from the Teal Pool Hide – note the lack of teal or other birds

I often describe Brandon Marsh as an all or nothing place – today it had almost all. There were some ringed plovers patrolling the edge of the water. One of them looked a little different to the others, it had more black on it and, on closer inspection (using the magnificent zoom capabilities of my telescope) I discovered that it had a black tip on the end of the orange bills. Likewise, the zoom also showed a distinctive eye ring on the other birds – so that would be one Ringed Plover and several Little Ringed Plovers. They were quite active and flew about the different islands. They also looked quite tiny compared with the redshanks that were wandering around in the slightly deeper water as well as along the shore (I love the whistling of the redshanks). Whereas the ringed plovers spent their time looking along the shoreline, the redshanks stuck their head in the water up to their eyeline. The sandpipers (common or green, no idea which) wandered along the mud, bobbing away, but not getting in too deep. There were also lapwing and oystercatchers on the islands, possibly nesting. A sleeping oystercatcher kept one eye on proceedings and a white butterfly wandered past – the sun must have come out.

Sand martins were there in abundance, zooming about and checking out the two sets of nests that have been provided for them – this is the only place I’ve seen sand martins – I hope they do well. There were a couple of terns near the tern raft – but the raft was occupied by two sleeping greylags – apparently they hand’t read the tenancy agreement.

There was a reed warbler singing outside the hide making his presence known. It would make brief flights upwards into the air, chest puffed out, wings back, then plummet down into the reeds and slowly climb up one of the stems and sit warbling away for ages. I can’t tell the difference between reed and sedge warblers and thought it sounded like a sedge warbler – shows how much I know. Someone recently told me that reed warblers just don’t stop singing. I always think of sedge warblers as being more scratchy and reed warblers being more rounded in their song. There was a man in the hide with an expensive camera lens who got some great shots who said it was a reed warbler. Later on he admitted he couldn’t remember whether it was the sedge or reed warbler that had the eye stripe – it is the sedge warbler and this had an eye stripe – I still have never seen a reed warbler! But at least I was right about the song – it was scratchy and he did sometimes pause for breath.

Wild Violet – so very pretty