Wednesday, 19 June 2013

Life without death in the life of birds.

During Springwatch 2013 there has, once again, been death of young nestling's. This happens every year and every year the presenters Chris Packham, Michaela Strachan and Martin Hughes-Games expertly put the viewers at ease by explaining why it happens and that it is all part of the circle of life. In this blog I will attempt to put this phrase, 'the circle of life' into numbers. Without death in the life of birds the world would become over run.

So lets start with some commoner birds. Currently the Blue Tit breeding population is about 3.3 million individuals. In each brood there are 8-10 eggs laid, so for purposes of this blog an average of 9 eggs laid. We must assume that this is 5 chicks per adult (CPA). Now, without predation or egg failure and assuming all of these chicks survive and are successful and every Blue Tit individual survives then the population would go from 3.3 million to 16.5 million in one year and that's not even considering second broods! In two years time assuming every Blue Tit from the year before breeds, the population would have gone up to 82.5 million Blue Tit's. It is unimaginable to think what it would be like.

Moving onto another common garden bird, Robins. The current population of individuals is 5.5 million. There  are 4-5 eggs laid, so lets say there are 5 eggs laid in each brood. We again, must assume that this is 3 CPA. The same rules apply as did for the Blue Tits, none of the chicks are predated or die from the cold or anything - They all survive. In a single year the population would go from 5.5 million individuals to 16.5 million. An increase of 11 million. The next year it will increase by 33 million to 49.5 million birds. Within two years of this 'world without death' the one Robin that hops around you while you dig will become 5 Robins or 10 Robins.

So you get the general idea that without death bird numbers would, obviously, increase dramatically. But to put this into perspective we need to think about those rarer birds, the ones you really want to see. Now of course we want to see our rarer, less seen birds increase but would this new world prove to much. Well let's take a look at the numbers.
Hawfinches. A fantastically powerful and beautiful bird. Everyone would like to see one but its not that easy with only 9600 individuals breeding in Britain. However, I'm sure you've guessed it, every single Hawfinch is successful, every chick juvenile and adult survive. The population is going to rise rapidly. Hawfinches have 4-5 eggs in a brood, so we will assume they have 5 - 3 CPA. the population will go from 9,600 to 28800 in one year, the next the population will be 86400 . In less than 4 years time Hawfinches will be as common as Robins are today. Imagine that while walking to the Bus station, or the shops and this wonderful powerful Hawfinch dives across you into the bush. Magnificent! -to a point. This would become such a regular occurrence that this wouldn't come into my mind it would be something more like " ooh what's that, oh it's only a Hawfinch." Now I'm not saying that I don't appreciate common birds because I do but the excitement isn't there when you see a common bird and that's what you expect when you see a bird like a Hawfinch.

Well there you have it, should predation and death stop completely then birding just wouldn't give you the same thrill it does today. This is, unfortunately, why we must accept what goes on during these programs. It's a fact of life and without it life would be considerably more boring. So go on, what are waiting for, go and find a rare bird and most importantly - Enjoy it! Happy Birding.

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