View From The Shed by Vilunteer Shaun - CH-CH-CH-CH CHANGES

CH-CH-CH-CH CHANGES

• If you can’t walk well on your first attempt, you’ll probably bump down on your nappy-clad backside but still be applauded for trying. Have another go, kid, you’ll get the hang of it. 
• If you don’t get enough food, you can usually just wander over to the fridge or cupboard and find something to eat. Or there’s always Deliveroo.
• If you find yourself in a dodgy area of an unknown town it’s a good idea to simply turn around and retrace your steps. The chances of you being mugged or worse are actually very low, despite what the press might say.
• If you’re cold and wet and night is falling then most of us are fortunate enough to have a warm home to go back to.

These are basic facts of being a healthy human being.

Now imagine you’re a bird

• If you don’t fly well on your first attempt, you’ll probably fatally crash or get caught by a predator on the ground.
• If you don’t get enough food you’ll starve and eventually die.
• If you find yourself in a dodgy area heavily populated by predators you’ll more than likely end up as a tasty snack.
• If you’re cold and wet and night is falling then the odds are good that you simply won’t wake up

These are basic facts of being a bird. Birds live on a knife edge. The odds of a songbird making it to adulthood are only around 20% - which means that only one in five chicks will go on to make eggs of their own.  Even in the darkest dark ages, human survival rates have always been much higher than that.

There’s an old joke that goes, How many librarians does it take to change a light bulb?

The librarian looks aghast and says, “Change? CHANGE????”

Apologies to my librarian friends but it’s true, most of us are resistant to change to a degree, and why shouldn’t we be? If it ain’t broke, why fix it? And Nature is the same. Thousands of years of minute amendments have gone into each creature filling a particular existential niche. There’s only a change if it’s necessary and even then, the change is infinitesimally small. One bird at a time, over many many generations. And eventually, a change is made to meet a need - and these needful changes are usually instigated by the availability of food.

Look up into a forest of Christmas trees. Yes I know that there’s no such species but at this time of year I’m contractually obliged to mention the ‘C’ word whenever possible. So look at those ‘Christmas trees’. It’s not unheard of to see Great Tits, Blue Tits and Coal Tits all feeding on the same Fir tree branch with the Greats nearest the trunk, the Blues in the middle of the branch and the Coals right out on the flimsy end, their slight frame allowing them to perch where the weight of the other two species would not be supported. Each bird feeds at the point that their weight is tollorated and they can get food while not being bothered by other species. Competition for food is one of the main problems facing a bird going about its daily life.

Evolution leading to niche feeding like this is fairly easy to understand. I can see that there’s a gap in the market so some birds will change (over many, many generations) to fill it. And they’re still doing so. Look at how Pied Wagtails are very much at home in well-lit car parks but their Grey and Yellow cousins won’t go anywhere near this human habitation. They’ve evolved to tolerate the bad air quality and abundance of people because the prize of relative warmth and safety (compared to open countryside) is worth it.

Many wading birds look very similar to me but the differences in the length of their beaks means that they can probe for food in different depths of mud. This is another example of niche feeding, filling an evolutionary gap allowing your species to access food unavailable to other birds. 

But the reason for the development of some characteristics is sometimes harder to discern. Why for example would most Buzzards - including the ones that we most commonly see in our Dearne Valley - have bare skin on their legs but a different species in mainland Europe - the Rough-Legged Buzzard - has (as its name suggests) heavily feathered legs. It’s only when you learn that the Rough-Legs spend much of their summers up in the Arctic that the reason for this adaptation becomes obvious. They’re pretty much the same as a regular Common Buzzard, but they have adapted to the harsher northern conditions so much that they are now genetically just that little bit different. 

Garden birds too show how small differences can change their appearance and habits. For example, recent migration studies of Blackcaps have shown that, whereas in the past birds would fly from Germany and Austria down into Spain or Portugal for the winter, following the warmth in search of natural food, now they are choosing to overwinter in Britain. It seems that as our winters are becoming less cold, the amount of food that we bird-loving Britishers put out for them makes it worth their foregoing the extra warmth of Iberia for the extra high quality food of Blighty. These birds are also seen to have thinner and longer beaks than those that still head to Spain. Birds wintering in that part of Europe eat mostly seeds. Those coming over the Channel find a more varied diet on our feeding tables and hangers, and this needs a more generalised beak. This is evolution as we watch and it’s being driven by you and I supplementing our garden birds’ diet.

And that leads nicely on to next week’s blog which is about what gifts you should give the birds for Christmas. Get your Santa hat ready.