Tuesday, June 01, 2010

Star Trek, Pokemon and relativity…a birding perspective!

Damn it's strange how your mind wanders, how it recycles old thoughts... or maybe it's just me. Came across this I'd written a few years back. Could have written it yesterday... except for the date of course...

All things are relative. Take today for instance. It’s relatively early on a relatively warm morning in late-March. I’ve come to a wetland site relatively close to where I live (Woolston Eyes) to see some relatively rare breeding birds (Black-necked Grebes). Not unusually, I have the place largely to myself, and so, apart from the omnipresent Black-headed Gulls, it’s relatively quiet in the little painted hide on No.3 Bed. I’ve already had relatively good views of at least nine grebes and am finishing the dregs of my now, relatively cold tea. As I scan the reed-fringed pool in front of me it strikes me, however, that since arriving an hour ago, I’ve seen relatively few other species (35 to be exact). Particularly conspicuous by their relative absence are the passerines, outnumbered, in terms of species, two to one by wildfowl, waders and gulls. Nothing remarkable in that, I guess – to use a metaphor, ‘What do I EXPECT to see out of a Torquay Hotel window… herds of Wildebeest sweeping majestically across the African Plains…?’ Unfortunately though, this quiet patch has given me the fidgets. I’ve got to be back in Runcorn in a few hours and so can’t decide whether I should stay and watch the grebes or shoot off somewhere in the hope of adding a few more species to the year list. If I stay, I might be lucky enough to see the Black-necks displaying, a first for me, but if they decide to take a break, I could be staring at the reeds for the next few hours. Decisions, decisions… In the absence of any quick solution (i.e. the lure of a local rarity) I decide to show a little enterprise and apply Spock-like logic to the situation in the hope of coming to a decision.

I’m sorry, that was awful - enterprise? Spock? Still, it worked! I decide that I’m going to stay and watch the grebes and NOT go somewhere else to try for a few more year ticks. Here’s why…

Whether a member of the UK400 club or a casual, weekend birder we’re all subject to two simple rules; (i) there are limits to what CAN be seen at a particular place and/or time and (ii) finding new species gets harder and harder as time goes on; a kind of ‘law of diminishing returns’. Why might this be? Well, the Vulcan in me tells me that it’s probably something to do with the relatively high ratio of vagrants to residents that we get in Britain. I’ll try to explain. As you may, or may not know, the current British List stands at about 556 species which is equivalent to about 65% of the species recorded in the Western Palearctic as a whole (our particular zoogeographic zone) but a mere 5% of the 9850+ extant species worldwide. As far as birds are concerned, therefore, Britain is, in the grand scheme of things, relatively impoverished - one reason perhaps why I’ve seen relatively few species today. More significantly however, is that, of all the category A, B and C species currently comprising the British List only 140 (i.e. a quarter of the total), are actually permanent residents here. I’d not really thought about this until now and was rather stunned that the figure was so low. Put another way, three-quarters of ‘our’ avifauna, EITHER (i) just visit when the weather elsewhere is relatively bad (i.e. winter and summer migrants; about 89 species), OR (ii) pass through on their way to somewhere nicer (i.e. passage migrants; about 30 species), OR (iii) find their way here entirely by accident (i.e. vagrants; about 297 species). No wonder I‘ve hit a dry patch at Woolston, most of the winter migrants have left, most of the summer ones have yet to arrive and half our small stock of resident species are more likely to be found in a wood, on a cliff or up a mountain somewhere! And as for the vagrants, well…they’re just that…vagrants…who knows where they’ll turn up!

Clearly then, there are limits to how many species a site can lay claim at a given point in the year, thus lowering the odds of seeing as much as you’d like on any one occasion. Obvious really, frustrating maybe, but fair enough. But then there’s the law of diminishing returns to contend with too. Imagine - it’s January 1st and the new, year list beckons. You rack up a respectable number of species and go to bed happy with the start to the year. As luck has it, you get out the next day too. You quickly find though that you’re seeing many of the same species and relatively few new ones. The following weekend arrives and you go out again…same story. In fact as the year progresses (apart from slight peaks in the spring and autumn) last year’s easily beatable total begins to seem less and less assailable because whilst your first 10 species took 5 minutes to bag, your last 10 look likely to take 5 weeks or 5 months! The weird thing is that even if you widen your search you’ll still hit this same wall… and what’s more, the same holds true for bird races, county lists, local sites, life lists, foreign trips and world lists. The first birds are easy to get, the next much harder, the next harder still - the only thing that changes is the scale.

The result of all this seems to be a kind of ‘levelling out’ of birding potential. Take for example well-worked sites, such as Woolston and one or two others. Obviously the more a site is visited in a given year the more species are likely to be recorded, but only up to a point. At Frodsham for example, the average would appear to be about 160 species, at Seaforth one recent report quotes 163 species, at Marshside it’s 168. I suspect the figures will not be that much different for Woolston, Inner Marsh Farm and Martin Mere either. Even allowing for the fact that these are necessarily minimal figures (some birds are bound to be missed), they aren’t as different from each other as you might expect. The actual species at a site may vary a little, year on year (which is why site lists are always longer than a site’s year list – if you catch my drift), but the number of species recorded at a site varies relatively little. A similar pattern emerges when you look at things at a county level; 1999 – Clwyd 225 species, Cheshire 229 species, Lancashire 240 species; 2000 – Cheshire 233 species, Lancashire 241… pretty consistent between sites and years. Now I’ve no idea what the number of species recorded in Britain as a whole is annually, but I wouldn’t mind betting that it’s somewhere between 350-380 species and that it doesn’t vary too much between years!

So what, if anything, does this tell us? Maybe it’s this. Birding is not Pokemon - you CAN’T get ‘em all! It’s as hard to see your first Storm Petrel if you’re weekender as it is to see your 160th local patch species or, if you’re a dedicated UK wide twitcher, any of the Nearctic thrushes. Whether you’re on Hilbre or Fair Isle, birds are no respecters of list length and no matter how often you get out or how many miles you eat up in pursuit of that illusive new species, at the end of the day you’re still just as likely to dip as tick! Some birds you‘ll find easily and see regularly and others you won’t – EVER! I guess that’s the beauty of birding - the experience is the same, whatever your level of expertise, however far you travel and wherever you end up. So, next time you’re about to dash off somewhere ‘else’ it maybe worth asking yourself why? As a wise man once said ‘Sometimes [Glasshopper?] there really IS no better place than ‘here’ and no better time than ‘now’. And as a pair of Black-necked Grebes rise up and run across the water in full display, I can’t help thinking, that at least for today, perhaps he has a point… beam me up Scotty!!!

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