The unsound approach

Cormorants: a new approach.

Are you worried about your inability to separate carbo from sinensis? Is your birding plagued by feelings of inadequacy every time you go near a reservoir? Have you had to stop twitching ducks, for fear that a cormorant may drop in, exposing your pitiful ignorance to your peers?

We at Punkbirder are aware that listers across the UK are being seriously hampered by their embarrassing failings in the cormorant department. We know that many of you are desperate to feel like decent birders again, but you can’t get past the second paragraph of the Birding World article without slipping into a narcotic coma. We are increasingly worried about the growing trend of fearful birders abandoning their local reservoirs, and instead wasting their time birding in cormorant-safe habitats, like coastal scrub and cliff-top fields.

But fear no more! Help is at hand.

Using literally minutes of experience in the field, we have developed a fail-safe method of determining cormorant identity, even from the poorest of brief views. Building on the excellent work by previous authors (Somesad & Bastard, 2005), we have established that the two forms can be confidently separated using a number of straightforward head and gular pouch measurements. For your birding ease, we have combined these features in a simple mathematical equation, the Cormorant Coefficient Calculation.

It couldn’t be easier. To perform the calculation, simply estimate the value of A (the angle of between gular patch base line and lower mandible). Next, calculate the tangent of this angle in radians and multiply by R (the ratio of bill length to throat depth, plus an estimate of the standard error, s.e.). Finally, to complete the calculation, divide this value by the reciprocal of the square root of your self-found list (L), multiplied by the speed of light squared (c2). And there you have it! If the resulting value is less than 150, your bird is definitely a carbo, whilst values greater than 30,000 indicate an obvious sinensis.

(Beginners may wish to fix a protractor to the end of their Swarovski’s, just until they fully get the hang of things.)

Once you have the simple calculation memorised, all your cormorant worries will be a thing of the past. You can even go back to enjoying the web's many great photo galleries of these beauties. Like this one…

Cormorant ID Gallery:

Classic carbo


These cracking individuals were all confirmed using the CCC.

Subtle sinensis


In good light, sinensis cormorant can be a really distinctive bird. The subtly different plumage tones and gular dimensions are shown well in these photos. Sharp-eyed observers will also note the characteristic stance of these individuals.

 All photos © J. Gilroy, A. Lees and A. Grosset, except the close-up of the cormorant head, which we stole from the web. Sorry…