Larus cachinnans

(last update: February 16, 2013)

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Peter Adriaens (Belgium)
Ies Meulmeester (Netherlands)

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cachinnans plumages

1cy cachinnans: November

Chris Gibbins, Grzegorz Neubauer and Brian Small, in "From the Rarities Committee's files - Identification of Caspian Gull. Part 2: phenotypic variability and the field characteristics of hybrids, (BB 104/2011) present Table 2 in their paper: "Percentages of sample first-winter birds with trait scores for selected plumage, structural and moult characteristics". On this page we repeat table 2 and illustrate each category with example birds. Some traits are very objective (especially measurements from pictures), other traits are very subjective and observers may interpret a single bird in different ways (e.g. leg length).
On this webpage, we repeat table 2 in different order, classified with "most useful traits" on top. The important traits are:
(i) bill length : depth ratio;
(ii) extent of scapular moult;
(iii) greater-covert pattern; and
(iv) primary projection.

(i) bill length:depth ratio, the ratio measured as in adults (for exact measurements, from feathering on top of bill to bill tip).
"0": measured 2,98
"1": measured 2,75
"2": measured 2,16
"3": measured 1,86
Score
Description
Herring
(n-85)
Caspian
(n=63)
Hybrid
(n=12)
0
very long and slim, with little/no visible gonydeal angle (L:D ratio >2.8) 
0
11
0
1
slim, slight gonydeal angle (ratio 2.4-2.79) 
3
67
37
2
intermediate (ratio 2.0-2.39) 
91
20
63
3
short and deep, well-marked gonydeal angle (ratio <2.0) 
6
2
0

(ii) extent of scapular moult (note: moult may progress slowly between October - March and therefore be careful when comparing 1W October samples to 1W March samples).
"0" 2CY Caspian Gull February
"1" 1CY Herring Gull December
"2" 2CY Herring Gull January
Score
Description
Herring
(n-85)
Caspian
(n=63)
Hybrid
(n=12)
0
no first-generation feathers remaining
13
92
78
1
a small number (<1/3) of first-generation feathers remaining
43
8
22
2
a significant number (>1/3) of first-generation feathers remaining
44
0
0

(iii) greater-covert pattern.

"0": 1CY Caspian Gull
"1": 1CY Caspian Gull
"2": 1CY Caspian Gull
"3": 1CY Herring Gull
Score
Description
Herring
(n-85)
Caspian
(n=63)
Hybrid
(n=12)
0
simple pattern with brown centres and sharp white edges, with no white vermiculation or notching
0
3
0
1
white edges with delicate notches or vermiculation; or dark brown centre with white tip to 1/3 of length (i.e. white restricted to tip or distal third)
0
63
12
2
clear white notches / barring creating a delicate 'piano key' pattern along the whole edge / feather; but much of feather dark
0
30
38
3
lots of white (more than 1/2 of coverts looking white) distributed along the whole feather, or a bold notching ('piano key' pattern)
94
4
50

(iv) primary projection.

"0": 0,63 in Caspian
"1": 0,55 in Herring
"2": 0,44 in Herring
"3": 0,37 in Herring
Score
Description
Herring
(n-85)
Caspian
(n=63)
Hybrid
(n=12)
0
very long (ratio >0.6)
6
72
56
1
moderately long (ratio 0.5-0.59)
38
25
33
2
medium (ratio 0.4-0.49)
45
3
11
3
short (ratio <0.4)
11
0
0

(v) ventral bulge (discussion on this trait of course are: "what is the division line?" and "is there a difference in birds in relaxed pose or alert individuals?").

"0": Caspian Gull
"0"?: Caspian Gull
"0"?: Caspian Gull
"1": Caspian Gull
Score
Description
Herring
(n-85)
Caspian
(n=63)
Hybrid
(n=12)
0
present
14
62
34
1
absent
86
38
66

(vi) first generation tertial pattern.

Scores for 1st gen tertial patterns in 1W cachinnans.
"0": Caspian Gull
"1": Yellow-legged Gull
"2": argentatus
"3": argenteus
Score
Description
Herring
(n-85)
Caspian
(n=63)
Hybrid
(n=12)
0
diffuse white tip (like Common Gull Larus canus)
1
65
33
1
fine pale fringe around distal portion (like classic michahellis), possibly also with some vermiculations
3
32
12
2
edges moderately notched
33
2
22
3
edges strongly notched and/or some dark barring or pale patches across the feather on some or all tertials
63
1
33

(vii) leg length (discussion on this trait of course are: "what is the division line?" and "is there a difference in birds in relaxed pose or alert individuals?").

"0": Caspian Gull
"1": Caspian Gull
"1": Caspian Gull
"2": Herring Gull
Score
Description
Herring
(n-85)
Caspian
(n=63)
Hybrid
(n=12)
0
long
0
14
12
1
moderately long
13
46
50
2
short
87
40
38

(viii) darkness of head and body.

"1": Caspian Gull
"2": Caspian Gull
"3": Caspian Gull
"4": Herring Gull
Score
Description
Herring
(n-85)
Caspian
(n=63)
Hybrid
(n=12)
0
totally white
0
0
0
1
reduced grey wash or streaking (confined to flanks and/or single streaks around nape)
0
41
0
2
light streaking/wash to head (incl. some dark around eye); isolated streaks/blotches on body. Overall, body looks more white than brown
17
43
22
3
well streaked: dark mask around eye and/or streaking covering the whole head/face; body with extensive but moderately dense streaks/mottles
68
16
78
4
strong and dense streaking/mottling on body and head making it appear almost wholly dark
15
0
0

(ix) second generation scapular pattern (note: from late November, plain grey upper scapulars normally are 3rd generation feathers, not 2nd generation; and by March many birds in fact show extensive 3rd generation feathers, not 2nd generation).

"0": Caspian Gull
"1": Caspian Gull
"2": Caspian Gull
"3": Caspian Gull
"4": Caspian Gull
Score
Description
Herring
(n-85)
Caspian
(n=63)
Hybrid
(n=12)
0
uniformly silvery-grey, darker patterning absent or very faint
0
8
0
1
silvery-grey background, pattern stronger than on 0, but lacks strong barring or central dark diamonds (only dark shafts and subtle anchors), with only a minority (one or two) of such feathers admixed
0
30
0
2
strong, contrasting shaft-streaks, anchors and/or dark central diamonds, but these more patterned feathers are less than 1/2 of all; ground colour creamy or silvery-grey, possibly with some grey feathers mixed in
0
30
0
3
strong pattern described in 2 on most (more than 1/2) of feathers, but possibly also one or two plain grey feathers or feathers with grey ground tone
4
17
12
4
all feathers contrastingly patterned (with dark cross bars or diamonds), lacking plain grey feathers; feather centres buffy-brown
96
15
88

(x) median covert moult (from michahellis we know moult is normally clustered in the inner coverts and upper tertials, but may extend outwards. Nonetheless, coverts hidden by flank feathers can, by definition, not be scored, so safely ratio = new feathers / visible feathers).

"1": Caspian Gull
"2": Caspian Gull
"3": Caspian Gull
"4": Caspian Gull
"5": Caspian hybrid
Score
Description
Herring
(n-85)
Caspian
(n=63)
Hybrid
(n=12)
0
all or almost all new (>75%)
0
0
0
1
51-75% new
0
13
0
2
34-50% new
0
20
11
3
10-33% new
0
35
0
4
one or two feathers moulted
1
13
22
5
no moult
99
19
67

(xi) greater covert moult (as median coverts; ratio = new feathers / visible feathers).

"0": Yellow-legged Gull
"2": Caspian Gull
"3": Caspian Gull
"4": Caspian Gull
"5": Caspian hybrid
Score
Description
Herring
(n-85)
Caspian
(n=63)
Hybrid
(n=12)
0
all or almost all new (>75%)
0
0
11
1
51-75% new
0
3
0
2
34-50% new
0
2
0
3
10-33% new
0
24
0
4
one or two feathers moulted
0
36
11
5
no moult
100
35
78

(xii) tertial moult.

"0": Caspian Gull
"1": Caspian Gull
"2": Caspian Gull
"3": Caspian Gull hybrid
Score
Description
Herring
(n-85)
Caspian
(n=63)
Hybrid
(n=12)
0
3 or more new
0
10
11
1
2 new
0
8
0
2
1 new
0
16
0
3
all old
100
66
89
Larus cachinnans 1CY UKK T-002446 November 28 2007, Deponie Pohlsche Heide - Minden, Germany (52°23'05N, 08°46'45E). Picture: Armin Deutsch.
Larus cachinnans 1CY PACZ October - November 2009, Deponie Pohlsche Heide - Minden, Germany (52°23'05N, 08°46'45E). Picture: Armin Deutsch.
Larus cachinnans 1CY PATL November 21 2009, Lubna, Poland. Picture: Michal Rycak.
Larus cachinnans 1CY & 3CY PATN November 2009 & March 2011, Germany & Switzerland. Picture: Armin Deutsch & Picture: Michel Gorgerat.
Larus cachinnans 1CY-2CY PCTN October 2012 - March 2013, Deponie Pohlsche Heide - Minden, Germany (52°23'05N, 08°46'45E). Picture: Armin Deutsch.
Larus cachinnans 1CY PDEB November 20 2010, Deponie Pohlsche Heide - Minden, Germany (52°23'05N, 08°46'45E). Picture: Armin Deutsch.
Larus cachinnans 1cy PHDK November 19 2011, Normandy, France. Picture: Tony Le Huu Nghia.
Larus cachinnans 1CY PHEN October & November 2011, Deponie Pohlsche Heide - Minden, Germany (52°23'05N, 08°46'45E). Picture: Armin Deutsch.
Larus cachinnans 1CY-3CY PHUK October 2011 - June 2013, Deponie Pohlsche Heide - Minden, Germany (52°23'05N, 08°46'45E). Picture: Armin Deutsch.
Larus cachinnans 1CY PKBC November 11 2011, Talsperre Quitzdorf, Saxony, Germany. Picture: Steve Klasan.
Larus cachinnans 1CY-2CY PKND October, November, December 2012 & March 2013, Deponie Pohlsche Heide - Minden, Germany (52°23'05N, 08°46'45E). Picture: Armin Deutsch.
Larus cachinnans 1CY-2CY PNNL August 2013-February 2014, England and France. Picture: Lee Gregory & Alasin Fossé.
Larus cachinnans 1CY PNUC November 15 2013, Warnemünde, Germany. Picture: Bernhard Kondziella.
Larus cachinnans 1CY PUDT November 20 2010, Lubna, Poland. Picture: Michal Rycak.
Larus cachinnans 1CY PUTK November & December 2010, Poland & Hungary. Picture: Michal Rycak & Gabor Papp.
Larus cachinnans 1CY PUVN November 01 2010, Lubna, Poland. Picture: Michal Rycak.
Larus cachinnans 2P16 1CY, November 01 2013, Siemień - fish ponds, Poland. Picture: Łukasz Bednarz.
Larus cachinnans 65P5 1CY, November 07-22 2015, Kent, UK. Picture: Michael Southcott.
Larus cachinnans 85P5 1CY, November 08 2015, Kent, UK. Picture: Michael Southcott.
Larus cachinnans 431P 1CY-2CY, September 2016 - June 2017, Katwijk, the Netherlands.
Larus cachinnans 1CY 042P November 03 2006, Deponie Pohlsche Heide - Minden, Germany (52°23'05N, 08°46'45E). Picture: Armin Deutsch.
Larus cachinnans 1CY 443P November 06 2008, Deponie Pohlsche Heide - Minden, Germany (52°23'05N, 08°46'45E). Picture: Armin Deutsch.
Larus cachinnans PLG DN-04725 1CY, November 24 2017, Katwijk, the Netherlands.
Larus cachinnans 1CY PLG DN-09082 November 18 2000, Deponie Coerde - Münster, Germany (52.00.39N 07.38.48E). Picture: Armin Deutsch.
Larus cachinnans 1CY PLG DN-1627x November 28 2007, Chevroux, Swizerland. Picture: Stephen Aubry.
Larus cachinnans hybrid 1CY PLG DN-21230 September - December 2007, Deponie Pohlsche Heide - Minden, Germany (52°23'05N, 08°46'45E). Picture: Armin Deutsch.
Larus cachinnans PLG DN-21448 1CY, November 04 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY PLG DN-28060 November 19 2012, Deponie Pohlsche Heide - Minden, Germany (52°23'05N, 08°46'45E). Picture: Armin Deutsch.
Larus cachinnans hybrid X025 1CY, November 16 2016, Katwijk, the Netherlands.
Larus cachinnans hybrid? 1CY XJCW Decembver 21 2011, Boulogne-sur-Mer, NW France. Picture: Jean-Michel Sauvage.
Larus cachinnans 1CY XMDK November 08 2013, Noordwijk aan Zee, the Netherlands. Picture: Frank van der Meer.
Larus cachinnans 1CY XNDH November 05 2013, Westkapelle, the Netherlands. Picture: Corstiaan Beeke.
Larus cachinnans hybrid? 1CY-2CY XTCV September 2012 - February 2013, Leeuwarden, the Netherlands. Picture: Jeroen Breidenbach.
Larus cachinnans 1cy 014:S November 15 2012, Rødvig-Stevns, Sjælland, Denmark. Picture: Lars Krogh.
Larus cachinnans 1CY 044:S November 02 2012, Witoszowka Reservoir, Swidnica, Poland. Picture: Mariusz Dabek.
Larus cachinnans 1CY 052:S November 30 2012, Witoszowka Reservoir, Swidnica, Poland. Picture: Mariusz Dabek.
Larus cachinnans 1CY 413:S November 11 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY E076 November 22 2011, Swidnica (Witoszowka Reservoir), Dolnoslaskie, Poland. Picture: Mariusz Dabek.
Larus cachinnans 1CY, 2CY & 7CY female KE74 2006, 2007 & 2012, Germany, Poland & Belarus. Picture: Jürgen Steudtner, Ruud Altenburg & Dmitry Goncharov.
Larus cachinnans? 1CY 2L7V November 04 2011, Jakuševec-Zagreb, Croatia. Picture: ringing team Luka Jurinovic.
Larus cachinnans 6L2V 1CY, November 01 2013, Siemień - fish ponds, Poland. Picture: Łukasz Bednarz.
Larus cachinnans HCV93 1CY, November 16 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY LIK EN01684 November 16-22 2007, Deponie Pohlsche Heide - Minden, Germany (52°23'05N, 08°46'45E). Picture: Armin Deutsch.
Larus cachinnans 1CY 347H November 20 2011, Jakuševec-Zagreb, Croatia. Picture: ringing team Luka Jurinovic.
Larus cachinnans? 1CY 379H November 20 2011, Jakuševec-Zagreb, Croatia. Picture: ringing team Luka Jurinovic.
Larus cachinnans VC2L November 2009 & June 2010, Rødvig-Stevns, Sjælland, Denmark. Picture: Lars Krogh.
Larus cachinnans 1CY-3CY-4CY V455 November 2008, February 2010 & January 2011, Denmark & the Netherlands.
Larus cachinnans 1CY SVS 90A71627 August & November 2010, Sweden & the Netherlands. Picture: Anders Åkesson & Ruud Altenburg.
Larus cachinnans 1cy, 21 November 2012, Boulogne-sur-Mer, NW France, Picture: Jean-Michel Sauvage.
Larus cachinnans 1CY, November 24 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY, November 24 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY, November 24 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY, November 24 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY, November 24 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY, November 24 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY, November 24 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY, November 16 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY, November 16 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY, November 16 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY, November 16 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY, November 16 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY, November 16 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY, November 16 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY, November 16 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY, November 16 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY, November 16 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY, November 16 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY, November 16 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY, November 16 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY, November 04 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY, November 04 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY, November 04 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY, November 04 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY, November 04 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY, November 16 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY, November 16 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY, November 16 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY, November 16 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY, November 11 2011, Talsperre Quitzdorf, Saxony, Germany. Picture: Steve Klasan.
Larus cachinnans 1cy, 30 November 2012, Barneveld, the Netherlands. Picture: Herman Bouman.
Larus cachinnans 1cy, November 13 2009, Westkapelle, the Netherlands. Picture: Theo Muusse.
Larus cachinnans 1cy, November 03 2007, Westkapelle, the Netherlands. Picture: Ies Meulmeester.
Larus cachinnans 1CY, November 21 2009, Rødvig Havn, Stevns, Denmark. Picture: Per Schans Christensen.
Larus cachinnans 1CY, November 05 2005, Stubben, Denmark. Picture: Anders Søgaard.
Larus cachinnans 1CY, November 11 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY, November 11 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY, November 11 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY, November 21 2010, Skagen Havn, Denmark. Picture: Knud Pedersen.
Larus cachinnans 1cy, November 23 2012, Ashdod, Israel. Picture: Amir Ben Dov.
Larus cachinnans 1CY, November 22 2009, Bärwalder See, Saxony, Germany. Picture: Steve Klasan.
Larus cachinnans 1CY, November 19 2013, Katwijk aan Zee, the Netherlands.
Larus cachinnans hybrid? 1CY, November 24 2016, Katwijk, the Netherlands.
Larus cachinnans hybrid? 1CY, November 24 2016, Katwijk, the Netherlands.
Larus cachinnans 1CY, November 15 2013, Katwijk aan Zee, the Netherlands.