Maps for Atlantic YLG showing results from Various
Classifications
• Primarily based on statistics held at:– http://www.nrossiter.supanet.com/ylg/
• First for adults from present studies
• Then from genetic studies of Liebers, D, Helbig, A J, and de Knijff, P,
• Azores data (in NR’s maps) are from other workers
Classification - Leg Colour: YL yellow legs
Classification - Mantle Shade: cf Med. michahellis: S same, D darker, P paler
Classification - Size: cf Med. michahellis: S same, Less smaller
Table 1: Biometrics (in mm) of Herring L .a. argenteus, Yellow-leggedand Lesser-black Backed Gulls L. f. graellsii.
Feature argen-teus
Medmicha-hellis
Atlantic Yellow-legged Gull graell-sii
NWIberia
W Iberia NWAfrica
Macro-nesia
Source Cramp(1983)
Cramp(1983)
Carreraet al(1987)
Cramp(1983)
Urban etal (1986)
Cramp(1983)
Cramp(1983)
wing 404-425
438-460 419 401-431 420-439 423-437 406-427
tail 160-170
169-179 - 158-169 162-170 165-173 152-164
bill 48.9-53.2
51.5-56.6
54.8 49.5-53.6
49.4-55.7
49.1-51.5
47.7-52.1
tarsus 60.5-65.2
64.5-70.6
65.6 60.3-64.4
61.6-65.0
62.7-64.7
60.3-65.2
toe 56.7-61.6
59.2-65.4
- 55.2-59.3
- 58.7-60.3
52.5-56.3
Table 2a: Further Biometrics (in mm) of Atlantic Islands Yellow-leggedGulls.
Feature Atlantic Islands Yellow-legged Gull
Macro-nesia
Azores Azores Canaries(East?)
Canaries-Tenerife
Azores
Source Cramp(1983)
Dwight(1922)
Dwight(1925)
Banner-man(1963)
Volsøe(1951)
Vaurie(1965)
wing 423-437 401-423 402-421
401-418 417-440 418-438
tail 165-173 162-170 162-171
162-170 - -
bill 49.1-51.5 50.3-55.1 50.2-54.3
46.5-54 - -
tarsus 62.7-64.7 61.7-66.6 61.6-66.3
62.5-65.5 - -
toe 58.7-60.3 52.3-56.0 52.2-55.2
- - -
Table 2b: Further Biometrics (in mm) of Mediterranean Yellow-leggedGulls.
Feature Mediterranean Yellow-legged Gull
Medi-terranean
Camargue BalearicIslands
IslasCharafinas
Source Cramp(1983)
Isenmann(1973)
Carrera(1987)
Carrera(1987)
wing 438-460 440-465 447 457
tail 169-179 - - 178
bill 51.5-56.6
56-61 57.4 56.6
tarsus 64.5-70.6
67-72 70.3 68.5
toe 59.2-65.4
- - -
Classification - Structure: T tall & proud, SS short legs & stocky, SF short legs & finer features
Adult Mediterranean michahellis, Royan, August 1991
Adult Yellow-legged Gull atlantis, Lanzarote, August 1992
Adult summer Yellow-legged Gull, Agadir, April 2000
Porto, March 2001, Pair YLG adults
Noja (Santander), August 1990, 3s Cantabrican YLG
Classification - Wingtip: MWMB much white & much black, LWMB less white & much black (>=80% solid
black triangle, <=30% mirror P9), MWLB much white & less black
Typical Adult Wingtip, Yellow-legged Gull, Agadir, April 2000
Typical Adult Wingtip Yellow-legged Gull atlantis, Fuerteventura, April 2000
Two Adult Yellow-legged Gull, Setubal, March 1999
Minho, April 2001, ‘YLG’ adult
Classification - Wingtip on P9 in South: LWP9 mirror on P9 <=20% of birds, MWP9 mirror on P9 >20% of
birds
Classification - Calls (long): A like argenteus (possibly deeper), M like Med. Michahellis, SG like shrill
graellsii, AM even argenteus & shrill graellsii
Map for Canary Islands
Classification - Calls (mew): A like argenteus, M like Med. michahellis, G like graellsii, AG mixtures of
argenteus & graellsii
Classification - Forms (NR): MM Med. michahellis, C Cantabrican Atlantic YLG, D dark Atlantic YLG, DC cline
from dark to Cantabrican.
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 has a more shallow haplotype and lower nucleotide diversity than atlantis– its haplotypes are a subset of atlantis, suggesting that
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 with no significant geographical variation while there is 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). Since northern atlantis is similar to michahellis in many respects, this suggests that southern atlantis contributed little to michahellis.
Classification - Forms (Liebers): MM Med. 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.
Convergence but ...
• Considerable agreement between studies.
• Some problems remain. – Liebers et al consider that the Azores should be in
the northern atlantis group
– but most earlier authors considered they belong to the southern group.
– However both Jonsson (1998) and Dubois (2001) did think the Azores form was distinct from the Canaries one.
‘YLG’: Mauritania, Azores; Kelp Gull (Birding World)
Convergence but … 2
• Another problem is the lack of genetic information on the Cantabrican form and the argenteus of south west France.
• Gene flow between atlantis and michahellis is probably continuing because of intersection at Gibraltar– Also michahellis is breeding now on the Atlantic
coast of France further increasing the likelihood of genetic exchange with atlantis.
The Atlantic-Mediterranean Intersection Zone
Visits up to 2001
• Morocco– Tanger (August 1993, 1994 and 2001)– Asilah to the south west of Tanger (August 1994)
• east Andalucia – Nerja and Estepona (May 1996; August 2001)
• west Andalucia – Cádiz, Conil and Barbate (August 2001)
• Straits of Gibraltar – Tarifa, Gibraltar and La Linea (August 2001)
Visits in 2002
• The detailed results of a more recent visit in June 2002 to west and east Andalucia are not available yet
• Visited Estepona, Tarifa, Barbate, Conil, Cádiz and Sanlúcar
• Some pictures will be shown
Three main forms in Zone in 2001
• Mediterranean Yellow-legged Gulls– marshes, lagoons and marismas
• dark Atlantic Yellow-legged Gulls – harbours and rocky cliffs in west Andalucia at Cádiz
and south-west of Tanger at Asilah
• Intersection Mediterranean/dark Atlantic Yellow-legged Gulls– harbours and rocky cliffs in the immediate west,
centre and east of area
In June 2002
• Numbers of Mediterranean Yellow-legged Gulls reduced but same habitat
• Large YLG colonies at Barbate cliffs and the islands off Cádiz were of dark form
• Gulls further east similar (provisionally) to those in August 2001
Features of Med YLG• Large size being considerably bigger than graellsii.
• Relatively pale mantle, lacking obvious blue tones.
• Boxy heads, long heavy bill with blunt tip, sturdy long legs equal in length to height of body above.
• Head moult: most (60%) brown speckles over forehead and rest of head (not neck); remainder fairly white still.
• Leg colour was a pale yellow with a slight orange tint
• Bill was a rather washed out yellow with a not very strong orange-red gonydeal spot.
• Calls: mew like a deep graellsii; the long deeper than graellsii and hoarser (more guttural).
• Only 35% with mirror on P9 (see Dwight)
Med YLG habitat - near Sanlúcar
Med YLG habitat - near Barbate
Med YLG habitat - near Conil
Med YLG - Conil August 2001
Med YLG - Conil August 2001 (with LBBG, Audouin’s)
Bimodal population at Conil -- very small numbers of dark YLG
Bimodal -- same group
Comparison from notes -- dark form showed (cf Med YLG):
Yellow-ochre legs (more ochre than pale yellow)
Shorter legs (2/3 body, not 1/1 body, similar in length to LBBG)
Darker mantle
Blue-grey tinge (not wane grey)
More mottled on front of head (not fine speckles)
More compact appearance
Rounded head (not boxy)
Size much smaller (slightly bigger than LBBG)
Tamer (kept in group while Med YLG left)
Med YLG elsewhere
• In August found in small numbers in harbours:– Tanger (7% in 2001, 10% in 1993-94) – Tarifa (20% in 2001)– Further east (cannot quantify)
• Figures for Tanger and Tarifa based on birds showing all features of Med YLG
Med YLG distribution: within red line in marismas
Atlantic YLG to West
• In August predominate in harbours at Cádiz (90km from Straits) and Asilah (50km from Straits)
• In June breed on cliffs at Barbate (40km from Straits) and on islands (forts) off Cádiz
• These colonies do not contain Med YLG
Features of YLG to west
• close to the dark form in:– mantle shade with a dark blue-grey colour – stocky structure– relatively small size– calls with shrill graellsii-like long calls and
graellsii-like mew calls.
• but perhaps slightly more white on P9
Cliffs at Barbate
Cliffs at Barbate 2
Two Atlantic YLG at Barbate
Two Atlantic YLG at Barbate
Adult Atlantic YLG, at Barbate, June 2002
Adult Atlantic YLG at Barbate, June 2002
Adult Atlantic YLG at Cádiz, August 2001
Adult Atlantic YLG at Cádiz, June 2002
Med/dark YLG distribution: Med: red line in marismas; dark: blue line on cliffs
Intersection Mediterranean/Atlantic YLG
• In harbours and rocky cliffs in the immediate west, centre and east of area:– some characteristics of dark Atlantic YLG– increasing tendency to Mediterranean form
Tarifa YLG (2s) June 2002
Tarifa adult, June 2002
Tarifa adult, August 2001
Estepona YLG, 1s/2w (juv,1s, adult), August 2001
Estepona YLG 2s-3w, August 2001
Estepona YLG, 3s, June 2002
Estepona YLG 2s, June 2002
Estepona YLG 2 ad, June 2002
Features Estepona YLG 1 (cf dark Atlantic YLG)
• Mantle: most are a similar blue-grey to that further west but a minority are a more leaden grey.
• Size: significantly larger.
• Structure: heavier:– more adults (30% as against 7-10% in Tanger) have boxy heads;
– legs are generally longer being 80-90% of the height of the body above compared to 70% in Tanger and 100% in Mediterranean michahellis.
– At rest the heavier heads were not tucked into the neck but were held with the bill pointing downwards as in Mediterranean michahellis.
Features Estepona YLG 2 (cf dark Atlantic YLG)
• Primaries: – slightly more white with 60% showing a white tip on P10 and 40% a
mirror on P9. – more black on P5 with 75% showing a broad band.
• Bare parts: bills were a rather dull yellow with a diffuse orange-red
gonydal spot; legs were a dullish ochre-yellow. • Calls: considerable variation perhaps reflecting the genetic
mixing. – Most long calls (55%) are of the shrill graellsii type as in Tanger but
30% are guttural, as in Mediterranean michahellis, and 15% are a deep argenteus.
– Mew calls show a similar mixture.
Features Estepona YLG 3 (cf dark Atlantic YLG)
• First-years: – 75% of the tertials were like those in the Canaries with
a narrow pale fringe;
– 25% were different to any found in the Atlantic showing, in addition to the narrow fringe, two slight notches on each feather edge.
Overall Statistics for Wingtip: C Cantabrican, DC Dark-Cantabrican cline, D Dark, I intersection, M Med YLG
(Conil)
P10- S
Tip%
LM%
SM%
P9%
P6-P10Tri -S
Sol%
SI%
LI%
P5 -S
BB%
TB%
IN%
P4 -PN%
C 27 73 27 0 85 28 0 30 70 16 6 63 31 10
DC 70 19 80 1 39 50 54 37 9 48 54 21 25 10
D 314 41 48 11 22 253 87 12 1 275 47 30 23 10
I 40 57 38 5 32 16 76 18 6 34 62 30 8 44
M 20 80 20 0 35 3 100 0 0 12 67 25 8 38
Overall Statistics for Calls: C
Cantabrican, DC Dark-Cantabrican cline, D Dark, I intersection, M Med YLG (Conil)
Long --graellsii
%
shrillgraellsii
%
Deeparg-
enteus %
MedYLG
%
Mew -graellsii
%
arg-enteus %
MedYLG
%C 0 0 100 0 0 100 0
DC + 68 32 0 85 15 0
D 8 58 34 0 75 25 0
I 0 77 11 12 85 6 9
M 0 0 0 100 0 0 100
Further East• Studies:
– Limited ones by NR in Nerja (west of Malaga, 170km E of Straits)
• 75% are large and heavy like Med YLG, 25% are small and with relatively slight structure
– Jonsson’s studies in Marbella• No major divergence from Med YLG reported
– Carrera’s studies at Chafarinas Islands (300km E of Straits)
• Indicate that biometrics are similar to those of Med YLG
Med/dark/inter YLG distribution: Med: red line in marismas; dark: blue line on cliffs;
inter: 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)
• Med YLG are invading both areas and breeding in a particular biotope (marismas, lagoons, salinas)
• dark Atlantic YLG 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 gene mixing zone across the Straits