the strange world of gull identification: how many gull species? nick rossiter nrossiter@supanet.com

The Strange World of Gull Identification:

How Many Gull Species?Nick Rossiter

nrossiter@supanet.com

Caution

• Gull identification and taxonomy is at a very fluid stage.

• Some of the terminology used here may not endure.

• But much new knowledge is being obtained and refined.

At one time -- large gulls were simple

All were Sea Gulls Conil, Spain June 2002

4 taxon here!

First Advance

• Herring Gull Larus argentatus

• Lesser Black-backed Gull Larus fuscus

• Great Black-backed Gull Larus marinus

Herring Gull adult Larus argentatus argenteus - SW

England, April 2002

Herring Gull adult Larus argentatus argenteus - SW

England, April 2002

Herring Gull adult Larus argentatus argenteus - SW England, August 2001

Great Black-backed Gull adult Larus marinus -- Seahouses, Sept

1991

Lesser Black-backed Gull adult Larus fuscus graellsii -- Seahouses, April 1992

Glaucous Gull adult Larus hyperboreus -- Seahouses, Sept

1990

Iceland Gull second-winter Larus glaucoides -- SW England, April

1990

Then races /forms appeared• Herring Gull:

– argenteus (France, Britain, Belgium, Holland)– nominate argentatus (Scandinavia)– smithsonianus (North America)

• Lesser Black-backed Gull– graellsii (Britain, France)– intermedius (S and W Scandinavia)– fuscus (N and E Scandinavia)

• Great Black-backed Gull– monotypic (one form)

Lesser Black-backed Gull adult Larus

fuscus graellsii -- Holland, May 1999

Lesser Black-backed Gull adult Larus fuscus graellsii/intermedius -- Holland, May 1999

Lesser Black-backed Gull Larus fuscus intermedius -- Bergen, Norway, May 1997

Finland for some!

Finland IGM 6: Tampere Tip, August 2002

Tampere Tip, Finland, August 2002

Lesser Black-backed Gull adult Larus fuscus fuscus -- Tampere tip, Finland, August 2002

BalticGull

Heuglin’s Gull adult Larus heuglini -- Tampere tip, Finland, August 2002

Heuglin’s Gull adult Larus heuglini -- Tampere tip, Finland, August 2002

Herring Gull Larus argentatus argenteus -- Seahouses, Sept 1991

Herring Gull Larus argentatus argentatus/argenteus -- Texel, Holland, May 1999

Herring Gull Larus argentatus argentatus -- Tampere Tip, Finland, August 2002

Herring Gull Larus argentatus argentatus -- Tampere Tip, Finland, August 2002

omissus

Herring Gull Larus argentatus argentatus -- Tampere Tip, Finland, August 2002

omissus

PJ Grant: Gulls - a Guide to Identification 1986

11 taxon

‘Southern Herring Gulls’

• Increasingly classified as new species. – Caspian Gull Larus cachinnans– Mediterranean Yellow-legged Gull Larus

michahellis– Atlantic Yellow-legged Gull Larus atlantis --

regarded as race of michahellis in some recent studies

Locations Visited

• From 1990-2002:– Canaries (every one)– Madeira– Morocco (North and South)– Portugal (all coasts)– Spain (Andalucia, Galicia, Santander)– France (SW)

• Mainly March -September

Map for Canary Islands

Agadir, Morocco (roof top colony, Amadil Hotel)

Classification of YLG - Leg Colour: YL yellow legs

Mediterranean Yellow-legged Gull adult Larus michahellis, Royan, SW France, August 1991

Caspian Gull first-winter Larus cachinnans, Norway, February 2001 (Frode Falkenberg)

Atlantic Yellow-legged Gull adult Larus atlantis, Lanzarote, Canaries, August 1992

Atlantic Yellow-legged Gull adult Larus atlantis, Agadir, Morocco, April 2000

Atlantic Yellow-legged Gull adult (two) Larus atlantis, Porto, Portugal, March 2001

Cantabrican Atlantic Yellow-legged Gull third-summer Larus atlantis/argentatus??, Noja,

Santander, Spain, August 1990

Classification - Mantle Shade: cf michahellis: S same, D darker, P paler

Classification - Size: cf michahellis: S same, Less smaller

Size comparison:

• Compared to michahellis:

• atlantis is: 5.8% shorter in wing;

4.6% shorter in tail;

8.2% shorter in bill length;

10.0% shorter in tarsus;

11.3% shorter in toe.

Typical Adult Wingtip, Atlantic Yellow-legged Gull Larus atlantis, Agadir, April 2000

Typical Adult Wingtip, Atlantic Yellow-legged Gull Larus atlantis, Fuerteventura, April 2000

Two Adult Atlantic Yellow-legged Gull, Larus atlantis, Setubal, Portugal, March 1999

Adult Atlantic Yellow-legged Gull, Larus atlantis, Minho, Portugal/Spain (Galicia) border, April 2001

Classification - Wingtip: MWMB much white & much black, LWMB less white & much black (>=80% solid

black triangle, <=30% mirror P9), MWLB much white & less black

Classification - Calls (long): A like argenteus (possibly deeper), M like michahellis, SG like shrill graellsii,

AM even argenteus & shrill graellsii

Proposed Forms of atlantis -- NR

Genetic Studies

• Liebers, D, Helbig, A J, and de Knijff, P, Genetic differentiation and phylogeography of gulls in the Larus cachinnans-fuscus group (Aves: Charadriiformes), Molecular Ecology 10 2447-2462 (2001).

• michahellis is derived from atlantis as the older lineage.

• atlantis has held a large population over a long period, residing in an area of relative climatic stability.

Differentiations found

• michahellis population is less diverse than atlantis

• Significant differentiation within all five atlantis colonies analysed.

• Unexpected differentiation was found between:• northern atlantis (Azores, west Portugal and

Galicia) and southern atlantis (Madeira, Morocco).

Classification - Forms (Liebers): MM michahellis, SA southern atlantis, NA northern atlantis. Samples came

from sites in green. Notes: extension (by NR) to Canaries needs to be

confirmed; Cantabrican omitted from study.

Atlantic Yellow-legged Gull Larus atlantis - Mauritania, Azores; Kelp Gull (Birding World)

The Atlantic-Mediterranean Intersection Zone

Three main forms in Zone

• Mediterranean Yellow-legged Gulls michahellis– marshes, lagoons and marismas

• Atlantic Yellow-legged Gulls atlantis– harbours and rocky cliffs in west Andalucia at Cádiz

and Barbate and south-west of Tanger at Asilah

• Intersection Mediterranean/Atlantic Yellow-legged Gulls michahellis/atlantis– harbours and rocky cliffs in the immediate west, centre

and east of area

michahellis habitat - near Sanlúcar

michahellis habitat - near Barbate

michahellis habitat - near Conil

michahellis - Conil August 2001 (with LBBG intermedius/graellsii, Audouin’s)

Conil, August 2001: One atlantis (front) with five michahellis

michahellis distribution: within red line in marismas

Cliffs at Barbate

Cliffs at Barbate 2

Two Iberian atlantis at Barbate, June 2002

Two Iberian atlantis at Barbate

Adult Iberian atlantis at Barbate, June 2002

Adult Iberian atlantis at Barbate, June 2002

YLG distribution: michahellis: red line in marismas; atlantis: blue line on cliffs

Intersection michahellis/atlantis

• In harbours and rocky cliffs in the immediate west, centre and east of area:– some characteristics of Iberian atlantis– increasing tendency to Mediterranean form

Tarifa michahellis/atlantis, second-summer, June 2002

Tarifa michahellis/atlantis adult, June 2002

atlantis wingtip

Tarifa michahellis/atlantis adult, August 2001

Estepona michahellis/atlantis 1s/2w (juv, 1s, adult), August

2001

Estepona michahellis/atlantis 2s-3w, August 2001

Estepona michahellis/atlantis, third-summer, June 2002

Estepona michahellis/atlantis 2s, June 2002

YLG distribution: michahellis: red line in

marismas; atlantis: blue line on cliffs; intersection: yellow line on cliffs

Width of Intersection Zone

• Barbate 40km W of Straits of Gibraltar

• Nerja 170km E of Straits of Gibraltar

• Does not appear to be greater than 210km.

• May be less if assess coastline more completely for colonies

Comparison of SW Spain and SW France (Yésou)

• michahellis are invading both areas and breeding in a particular biotope (marismas, lagoons, salinas)

• Iberian atlantis in Spain appear to occupy a similar role to the argenteus in France, breeding on cliffs, islands and forts in SW Spain

• additional complication in SW Spain is the potential gene mixing zone across the Straits

Four Taxon at Conil, June 2002

LBBG intermedius michahellis Audouin’satlantis/michahellis

Work of Dwight

• Jonathan Dwight, an American, studied skins of gulls from all over the world.

• Dwight, J, (1922), Description of a new race of the Lesser Black-backed Gull, from the Azores, Am. Mus. Novitates, 44: 1-2.

• Dwight, J, (1925), The Gulls (Laridae) of the World: their Plumages, Moults, Variations, Relationships and Distribution, Bull. Amer. Mus. Nat. Hist. 52: 63-401. In NHS library

Dwight

• First proposed atlantis (1922) as new taxon as race of LBBG -- Azorean LBBG -- based on studies of Azores and Canary specimens.

• Recently some workers have been claiming ‘true atlantis’ is only present on the Azores and actually basing whole classifications on this quoting Dwight as authority.

Dwight -- Extract from 1925 paper - range of atlantis

Lessons

• Read original texts before quoting from them.• Range of Dwight’s atlantis is very close to

that of Southern atlantis derived in present study and in the genetic study of Liebers.

• Dwight’s work was very systematic -- pioneering painstaking approach.

• He also noted wingtip pattern of michahellis in extreme W was like atlantis

So how many species?• Not settled but genetic and morphological studies are indicating

a number of splits.• Most of the former Herring Gull races are emerging as new

species (not argenteus though). • LBBG forms count only as one species. • Identification is another problem.• Many differ at the population level but individuals cannot be

identified with certain.• Problems of intersection areas. • Current research concentrating on birds of known origin

(colonies, ringing).