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.

Spot the cuckoo egg

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.

A Walk in the Park

There was a bit of sunshine on Sunday afternoon, so we grabbed the opportunity to go for a walk around the Country Park.  To be honest, I wasn’t expecting to see much as the weather had been a bit dull, wet and cold, but I was pleasantly surprised.

At the start of the walk we were greeted by numerous flowers, filling two of our senses with bright colours and heady scents, then we heard before we saw more than one song thrush singing for all he was worth, a female blackcap off to her nest with take out in her beak as well as the always present chaffinches, male and female.

It was, however, the number and variety of insects that surprised me the most considering the weather of the last few days.  Although I only saw a couple of white butterflies, the umbellifers (mainly hogweed I think) were flowering away and teeming with life.  I saw bees, flies and hoverflies galore, including this really pretty hoverfly that I had never seen before.

Hoverfly
Hoverfly

There were also a number of insects flitting about in the sunshine that caught my attention.  Some of these finally settled on leaves and had the biggest antennae I had ever seen.  They looked moth-like, and on googling for info discovered that they were longhorn moths (Nemophora degeerella) – certainly well-named.  According to the UK Moths site, the males (which have the long antenna) ‘dance’ in the sunshine in May and June and are quite numerous.  These were a first for me however.  This picture below shows how long the antennae are – about three times the length of the body.

Longhorn Moth
Longhorn Moth

So, the moral of the story is, there is something of interest whatever the weather.

Winding Down

After a bit of a hectic week (if only by my standards) I decided that Friday would be a day for doing the things in life that make me happy. This inevitably means photography or birdwatching and definitely a good walk. So, once more, I combined the two into one trip and spent an hour at Ryton Organic Gardens looking for a good photo opportunity and some inspiration for my flower garden, followed by an hour at Brandon Marsh.

I took a few photos that I quite liked, but I am not sure that I obtained much inspiration. Many of the flowers were still looking good, but I am not sure how much will be there in a couple of months time. There was also a fair amount of clearing being done, preparing the vegetable beds for Winter. The apple trees look as though the harvest will be a good one, ready for their Apple Day on 5th October, but, unfortunately I don’t have room for an orchard.

Brandon Marsh always seems to be an all or nothing place, and this week was closer to nothing. I didn’t have my ‘scope with me and was reliant on a small pair of binoculars, which meant that I probably missed quite a bit of what was on offer. However, no matter what the state of the bird population there it is always a relaxing place to walk around. The trees are starting to change colour and the Viburnum Opulus (Guelder Rose) were full of berries.

There were lots of lapwings and gulls about, and a red kite had been seen earlier (maybe that was responsible for the expensive glassware on show in the Carlton hide?), but there was a bit of a dearth of birdsong in the woods. I shall have to have a wander to the Country Park to check on the state of things there (any excuse for a walk!).