Saturday, 30 July 2016

Medway seagull genera for dummies

The other day someone, after lecturing me on why a Caspian Gull is a 'full fat tick' for a birder, then tried to tell me a Black-headed Gull was Larus ridibundus.

Eager to say the dang word out loud, I corrected them: "Chroicocephalus." 
Having never pronounced it before, I basked in the glory of my kroi-ko-sef-alus, as it must have been at least half right. Blank look. I had a second go- "Chroicocephalus ridibundus."

A look of disgust came over their face. "Oh I don't go in for all these changes to scientific names. And all the messing about with the scientific order. People should leave things be."

Yup, many of the scientific names changed a few years back.

The birding world is messy. Neatly evidenced by the Taxonomic Sub-committee of the British Ornithologists' Union when they announced they would adopt an 'intermediate taxonomy' for UK gulls back in 2007. Intermediate? Was that really as half-baked as it sounded? An early Brexit from all the forward thinking by our foreign friends?

Of course, evolution is messy, it doesn't stand still. And our abilities to identify the genuine differences increases. Advances in species definition and DNA analysis have pushed things to the limit (for now).

Taxonomy, the naming of a species is messy, but fun. Works rather like the game 'Six degrees of Kevin Bacon'. In this case, eight degrees of taxonomic ranks. In taxonomy every goes back to the level where everything meets up, the wondrous top level labelled "Life". Each level below that sees things sharing more specific attributes branching out. Playing the game through to the rather specialist 'level eight', where you pin down a critter to an exact species, is where most headaches are.

Some species are old, some are relatively new, some are, well, evolving. But for birders, it comes down to making evolution fit into a field guide. A new species described can add to their 'life list'. Think of it as real-life Pokemon Go. Gotta tick 'em all. Changes in the recent past have seen Yellow-legged Gull and Caspian Gull move out to full species status from under the wing of Herring Gull. Birders happy. But make a change a level up, at family? Birders sad. Many are just not really interested.

For this post, I'm very interested in the final three levels of the game of Life. In third place, you have the family. Panic ye not, those of the old field guides, because nothing changed at this level- all gulls are all still in the Laridae family. You can still call them Larids, and you can call yourself a Laridophile.

Below that comes genus (plural, genera) and what we birders know as the first part of the scientific names we see in our field guides, e.g. Black-headed, old school Larus, new school Chroicocephalus. For things to be put in one genus they  need to share a common ancestor with others who have same attributes- those that have that same common ancestor but different attributes get bumped off into different genera.

Only then do we nail to the final level, the species (as marked out by the second word in that scientific name- in the Black-headed, ridibundus).

What happened was several species moved out of the Larus genus- years ago they had looked to have been of the same close-knit group, but are now found to be subtly different. It has been decided there are now eleven recognised genera within the gulls worldwide.These eleven genera have only really been in use for a little over a decade, and for most of us our birding 'careers' are older than that. Small wonder we struggle to adopt. Which is silly considering the same people are responsible for all the splitting at the next level down, at species, giving us our wanted ticks.

This was my non-negotiable point in that conversation- if this birder wanted to tell me Caspian Gull, something a few decades ago most of us had never heard of as then just a race of Herring Gull, is now a species because it fits one (or more) of the various definitions of a species floating around out there, then surely they had to accept changes at other levels. Black-heads can't Larus any more.

Of course, we parted without any agreement.

As I walked home, I tried to list off what gull families are on the Medway nowadays. I failed. Curse these changes(!)

So as punishment for me, but (hopefully) a bit of fun for you, here's a dummies guide to the present (intermediate) gull families with a touch of added pedantry about the weird 'latin-y' words used, to help them make more memorable. Plus a sort of systematic list of the species in each family known up to turn most frequently on the Medway.

Pay attention. If you stop me on the sea wall, I will be testing you.


The Laridae families of the Medway:


1) - Xema

Monotypic (there's only one species within this family). Based on forked tail and black bill, separated from the once closely-related (south American) Swallow-tailed Gull by both behavioural and ecological differences- and by mitochondrial DNA.
Off to a flying start- Xema is a completely made up word- it means absolutely nothing(!) This happens a bit in taxonomy "...some authors having found difficulty in selecting genetic names which have not been used before, have adopted the plan of coining words at random without any derivation or meaning whatever..." Strickland, 1842. This particular meaningless word was dreamed up by Edward Leach (of Leach's Petrel fame), so blame him.

 - Sabine's Gull Xema sabini 
Sabini refers to ornithologist Sir Edward Sabine, more noted as a geophysicist who researched the earth's magnetic field. Who also did some some bird-spotting.
Status- Rare; essentially a pelagic species, sneaks onto the Medway list on basis of a handful of old records into the Medway mainly off Grain, one even making it up as far as Bartlett Creek. Best hope of ticking your own? Watching from Queenborough in an autumn hooley.


2) - Rissa

Short legs and reduced hind claw keep this species out of the Larus grouping (was once Larus rissa).
The word comes from the Icelandic name for the bird, Ritsa, or, in old Norse, Ryta.

 - Black-legged Kittiwake Rissa tridactyla 
Tridactyla is 'three-toed'. Kittiwakes have a reduced hind claw.
Status- Scarce; small numbers can be encountered in autumn and winter. More often found in the outer estuary, or main channel, often following shipping. From time to time small flocks can be blown into the estuary, when they will sit loafing in the main channels, or flighting around the estuary looking for a clear exit.

Part of a distant line of Kittiwakes resting in Bartlett, January.
Crippling views, eh?
Why no-one else bothers seawatching here I guess.
A good 'scope from Horrid or Bloors is your best bet...


3) - Chroicocephalus

The 'hooded' species group (Greek- 'to stain' and 'the head'). As they evolved, many of the smaller gulls developed a breeding plumage, mainly to help overcome the usual aggressive tendencies towards each other. Those where the dark plumage only goes part-way down the back of the neck are in this new family.

- Black-headed Gull- Chroicocephalus ridibundus
Ridibundus  means laughing.
Status- Commonest gull on the estuary. If you can't manage a four-figure count on a day in the field, you're not really trying.





4) - Hydrocoloeus

From 'water' and 'webbed foot'. Another family that is monotypic, having just the one member. As for clearly defining it, we're into the black arts of morphometrics. Measurements. Things that don't line up the same as in other families. For the layman, think of it like cars. Someone looks the shape and says 'that's a BMW'. Or looks at a pic of under a bonnet and says 'clearly a Renault'. It's beyond us mere mortals. It has behavioual differences which separate from other hooded gulls, but some argue it should be with Sabine's (and Ross's thrown in for good luck).

 - Little Gull Hydrocoloeus minutus
Minutus is one of the easier species names to translate. Small.
Status- Rare in spring, scarce in autumn and winter, often found in small numbers in rougher weather, the odd bird lingering for a couple of days thereafter.

Little Gulls, loitering off Bartlett, January



4) - Ichthyaetus

The 'black-headed' species group. Ikhthus = fish, aetos = eagle. Absolutely no idea why(!) The guy who first coined it did so back in 1829, so can't really ask. All I know is if anyone wants to get competitive and pushes me for the size of my list, I'll make up a figure and point out it includes Fish Eagle. People usually leave me alone after that.

 - Mediterranean Gull Ichthyaetus melanocephalus;
Melano 'Black' and cephalus 'head'. All birders know this trivia- L. ridibundus, the Black-headed Gull, doesn't have a black head- it has a brown hood in breeding plumage. Med Gull does. Common name fail.
Status- From mid-autumn through winter, difficult to locate other than ones/twos until the spring passage gets in gear in February, after which, hard to miss.

Med Gull, Sharp's Green car park, November.
Just take some bread.


5) - Larus

The 'white-headed' species group. Greek for, well... gull. Essentially the majority of the larger species, most with no real breeding plumage so often referred to as the 'white-headed gulls'- in the winter adults may well have a more streak-headed appearance, but such seasonal differences are never as black-and-white as in the smaller gulls (pun intended).

 - Common Gull Larus canus
Canus
means 'grey'.
Status- Absent only during the breeding months, never in large numbers, except when coming to roost, although prefers the more open areas of water.

 - Lesser Black-backed Gull Larus fuscus
Fuscus is latin for 'dusky, or 'brown'.


Status- breeds in small numbers, with a scattering of over-summering immatures; marked increase during the rest of the year. Hard to miss.

 - European Herring Gull Larus argentatus
'Ornamented with silver'.
Status- All over the shop. 2016 has seen a big increase in the numbers of summering immatures.

Best. Herring. Gull. Nest. Ever.


 - Yellow-legged Gull Larus michahellis
A spelling error. The good German Doctor after which this bird is named was actually called Karl Michahelles, most well known for his work on Yugoslavian birds in the early 19th century. He honoured a few people by immortalising them (e.g. a friend Franz Neumayer- Rock Nuthatch Sitta neumayer) with the correct spelling and then ended up wrongly recorded himself.
Status- Scarce late summer, rare at other times of year. Under-reported, mainly due to the inconsiderate behaviour of all the white-headed gulls to loaf a long ways offshore. Check through any large gulls changing pre-roosts during a rising tide at the right time of year (now). Or get lucky when a few large gulls decide to visit fresher waters at the heads of creeks at low tides. This link on summer occurrence/appearance is as good a place to start as any.

 - Caspian Gull Larus cachinnans
Yet another word for laughing.
Status- Rare late summer vagrant. Also under-reported, also extremely inconsiderate. Much rarer, best bet again about now during the post-breeding dispersal. And this link on summer occurrence/appearance is a good starting point.

 - Iceland Gull Larus glaucoides
Oides means 'resembling'. So, resembles a Glaucous Gull. So, no need to ever feel bad if you confuse them then?
Status- Rare winter vagrant, mainly fly-bys, possibly overlooked. Smart money would be on a late afternoon flight back into the Medway from the Greater Thames. Or try one of the 'birding cruises' and work through the mid-Channel loafers.

 - Glaucous Gull Larus hyperboreus
The Hyperboreans were a mythical race that lived 'beyond the north winds'. For the Greeks and their limited map of the world, who came up with the story, that would equate to somewhere just beyond Thrace. So, northern Bulgaria then.
Status- Rare winter vagrant, just a handful of records, mainly fly-bys, possibly overlooked. I presently dream of finding one heading into the Swale behind a Queenborough fishing boat.

 - Great Black-backed Gull Larus marinus
A simple one to finish on- 'marine'.
Status- Scarce in summer, regular in low numbers throughout the rest of year. Loves mid-estuary. Big 'n' black, and easy to identify.



And there you have it.

After ploughing through that, I think I might well now just go back to lumping the whole lot as 'seagull'.

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