Thursday 2 January 2020

The Expert View

Including the recent pair of birds at Kilmington WTW my winter tally of Siberian Chiffchaffs is now five. Or is it? Are these five birds actually Siberian Chiffchaffs? What exactly is a Siberian Chiffchaff? What about fulvesecens? Is a fulvescens a tristis? What about so-called 'intergrades'? And so on, ad nauseum. To be honest, reading about all this stuff could easily drive you nuts. Why? Because you are constantly presented with one expert view after another, and they don't all tally. So who is correct?

Here's a completely different scenario...

A golfer is standing by his ball in the middle of the fairway, trying to decide how far it is to the hole, and which club he will therefore need. He invites ten expert golfers to offer their opinion. All ten do the same thing. They peer towards the green, estimate the yardage to the hole and offer their view. Some reckon he'll need a six-iron, some a five-iron, one thinks he'll manage with a seven-iron, and so on. So, several different views. Another expert comes up, asks our friend how far he reckons he can hit a ball with each club, then takes a surveyors tape and measures the distance to the hole before offering his opinion. Which expert view would you take?

I am still mid-research with a lot of reading yet to do, but one thing I can say. When it comes to how a bird looks, well, the assessment of colour and tone is a bit subjective, and photographs may or may not tell you the truth. But there are a couple of things you can effectively 'measure', and would therefore seem to me more useful if you want to make an objective assessment. And they are DNA and sonograms. Going on what I've learned so far I would say all my pale and interesting Chiffs would likely return tristis DNA, and if I were to hear them call (just the one so far) and record it, the resulting sonogram would probably be a nice, almost-flat bar at around 4.5 kHz, which would match typical tristis.

I suppose my point is this. When gauging which expert view to listen to, ask yourself what it's based on. For example, how much 'measurement' has been involved, and how recently? Expert views change - or should do - when new criteria or data present themselves. Even our golfing expert with the tape would need to change his opinion if a monstrous headwind began to blow.

How are you on white-winged gulls? Not too tricky, you think? Allow me to present you with an expert view on the field identification of Iceland and Glaucous Gulls...

This is from the 1946 London Bird Report

So, in 1946 one expert view maintained that Iceland Gull was not reliably separable from Glaucous. I don't know how long that view held sway, but hands up who agrees with it now... What, nobody? Of course not. Since then much has been added to our collective knowledge, and it'll be a very rare occasion that the identity of a white-winger is not immediately apparent.

So far then, this is where I've got to...

Is the expert view based on something measurable?
Is it current?

Yes, and yes again? When it comes to expert views then, give that one, at least, some weight.


  1. Gav, with ID I guess it's that balance between 'defined minute detail' and 'gut instinct first impressions'.

    Does that balance depend on the audience? And where and what level of ID matters?

    A beginner birder would be satisfied with a separation between Chiffchaff and Willow Warbler. Where Birding Frontiers level wouldn't settle for anything less than a total taxonomic assessment with all intermediate possibilities taken into account to boot.

    With the Siberian Chiffchaff, the call would be a clincher based on other basics. Makes things simple when one diagnostic feature separates the chiff from the ch....

    I'll get my coat.

    1. Ric, I guess what I am trying to analyse is this:

      When you are looking at a bunch of wintering Chiffs at a SW sewage farm, and you come across an obviously pale one, how much information do you actually need in order to say it's a Siberian Chiffchaff?

      To put it another way, a very simplistic way: what are the chances that it isn't?

      I am gradually coming to the conclusion that the chances your pale Chiff is anything but a tristis are so slim as to be negligible.

    2. "...chiff from the chaff!"

      I missed that at first reading. Very bad, Ric! Very bad... :-)