Herring Gull- Zilvermeeuw (argentatus & argenteus)

(last update: December 15, 2011 )

Herring Gull adults April

Introduction

This website deals with the Herring Gulls of the taxa argentatus and argenteus. Argenteus is an abundant breeding species on Iceland, Britain, NW France, Belgium, the Netherlands and N Germany. The taxon argentatus breeds in NE Europe, from Denmark, the coast of the Baltic Sea, Scandinavia and coast of the White Sea. In the centre of the breeding range (Denmark and the NW German coast), birds show intermediate characteristics, indicating there is a cline in argenteus-argentatus. Argenteus in Western Europe is pale-backed, slightly smaller and with relatively much black in the wing-tip; argentatus in the NE Europe is larger, slightly darker on upper-parts and show less black in the wing-tip.
Due to the large breeding range, there is much intra-specific variation in argentatus, with most large, powerful birds in the northern populations, showing the most darkest upper-parts, longest wing and most white in the outer-wing. In this region, some populations may hold substantial number of yellow-legged argentatus. (referred to as "Finnmark yellow-legged argentatus"). In adult plumage, the black sub-terminal spot on P5 is often lacking or strongly reduced to a diffuse streak, broken at the centre. Sometimes P6 lacks black as well. 
In the Baltic region, other yellow-legged argentatus populations occur ("Baltic yellow-legged argentatus"), with adults showing even brighter yellow legs in summer and the upper-parts only slightly darker than West European argenteus, still much paler than Yellow-legged Gull (michahellis). Those Baltic argentatus often show a black sub-terminal spot on P5 in adult plumage.
On these web-pages, we largely follow P.J. Grant: "Gulls, a guide to identification" and E.K Barth's publication as Contribution No. 86, Zoological Museum, University of Oslo: "The circumpolar systematics of Larus argentatus and Larus fuscus with special reference to the Norwegian populations".

adult Herring Gulls - primary pattern

The differences between typical western argenteus from the U.K. and northern Scandinavian argentatus is rather straightforward on primary pattern P5-P10. However, there is a gradient and overlap in features of birds from populations in northern Germany, Denmark and southern Norway. 
Identification is even more challenging in birds from Baltic populations, which show both characteristics of argenteus and argentatus, but sometimes also of the southern taxa michahellis and particularly cachinnans.
Adult birds from the western populations argenteus show more black in the outer primaries, compared to northern argentatus. In argenteus, P5 normally shows small black sub-terminal markings, concentrated on the outer-web as a clear-cut black angular spot and in some birds extending on the inner-web as a diffuse streak. There may be some black on P4 as well, although this might be a clue for near-adult birds. In argentatus, especially from far northern Scandinavia, the black marking on P5 is completely lacking or is very limited and diffuse.
Argenteus
often has a black sub-terminal band on the top of P10, dividing the tip from the mirror. If the black sub-terminal band on P10 is broken, there is often still black on the inner and outer-web's edge of P10. Normally argentatus lacks sub-terminal markings on the outer-web of P10.

Baltic argentatus often have the black marking on P5 confined to the outer-web as a single rectangular small black square, with well-defined borders (not diffuse as in most Finnmark birds). In most Baltic birds, the white tip of P10 fully merges with the mirror, without a single sign of a sub-terminal band. The greyish-white 'tongue' on the inner-web is often broad and continues far down P10, almost creating a thayeri pattern on P10. The shape of the division line between greyish tongue and black outer-web can be an identification clue: In cachinnans this division line often makes a strong angular curve and has a smooth straight line, unlike the pattern of Herring Gulls, which often show a "saw-blade" motive or otherwise much irregularities along the division line. Sometimes wear of the outer primaries may be useful as a first indication of origin: An early moulting species as cachinnans on average show more abrasion in the feathers than later moulting argentatus.

Extensive research on the P10 pattern of Scandinavian argentatus was done for Norwegian birds by the Norwegian ornithologist Edvard Barth, and is presented in the table below. 

Table 4 from E.K. Barth, The circumpolar systematics of Larus argentatus and Larus fuscus with special reference to the Norwegian populations, 1968. 200 Norwegian birds. (Notation converted to what we use in the texts, MM).
locality sample size tip pattern P10 tip pattern P9 colour of P10 inner-web black present from P10 to:
1 2 3 4 1 2 3 4 5 1 2 3 5 6 P7 P6 P5 P4
East Finnmark 15 n 10 1 2 2 5 4 1 1 4 5 7 3 12 3 - 10 5 -
% 67 7 13 13 33 27 7 7 27 33 47 20 80 20 - 67 33 -
Tamsöy in Central Finnmark 33 n 17 7 6 3 10 10 6 0 7 12 20 1 23 10 - 19 13 1
% 52 21 18 9 30 30 18 - 21 36 61 3 70 30 - 58 39 -
Troms 29 n 17 8 3 1 11 9 4 1 4 3 20 6 24 5 - 24 5 -
% 59 28 10 3 38 31 14 3 14 10 69 21 83 17 - 83 17 -
Bodö and Röst 32 n 15 10 3 2 19 3 5 0 3 3 24 5 27 5 1 18 13 -
% 50 33 10 7 63 10 17 - 10 9 75 16 84 16 3 56 41 -
Tarva 20 n 8 7 3 2 11 5 4 0 0 10 8 2 12 8 1 7 10 2
% 40 35 15 10 55 25 20 - - 50 40 10 60 40 5 35 50 10
Stavanger and Lindesnes 42 n 18 13 4 6 23 12 3 2 2 15 23 4 37 5 - 13 29 -
% 44 32 10 14 55 28 7 5 5 36 55 9 88 12 - 31 69 -
Oslo Fiord 29 n 19 6 3 1 20 1 4 1 2 12 14 3 24 5 - 17 12 -
% 66 21 10 3 71 4 14 4 7 42 48 10 83 17 - 59 41 -
.
1: all white
2: trace of black near tip
3: incomplete black bar near tip
4: complete black bar or black tip
1: broad white band over both webs
2: white spot on both webs
3: white spot on inner web only
4: no white spot present
5: 'thayeri-pattern'
1: like mantle colour
2: slightly lighter than mantle colour
3: markedly lighter than mantle colour
5: relatively sharp border between black and grey
6: gradual transition from black to grey

Especially birds from north Scandinavian Finnmark may show the characteristic 'thayeri' pattern in the outer primaries P9 and P10 (column 5 of tip pattern P9 in the table). This pattern is named after the Thayer's Gull, which often shows a particular pattern in the outer primaries: the mirror and the white tip merge and are connected to the pale inner-web (see this image). In other words: the black medial band of the outer-web doesn't fully reach the edge of the inner-web and there is no sub-terminal band. In Thayer's Gull this pattern may be very obvious and, together with the 'string of pearls' may be indicative for identification. 

Primary moult timing and strategy

By October the majority of adult Lesser Black-backed Gulls moulting the outer primaries. There is a clear difference between presumed birds lingering around and birds which will probably migrate further south quickly. The difference can be found in the primary moult strategy. 

Some adult have a large moulting gap in the central primaries (for example P8-P10 old and only P4 fully grown and P5 still slightly shorter than P4) by the first days of September. It is hard to believe these birds will travel large distances non-stop as such moult gaps are highly inefficient for this migration pattern. Probably these birds, which can be found moulting in a period roughly from late August to late November stay in the area throughout their primary moult. They migrate further south either forced by cold winter or when the primaries moult arrives at the far outer primaries.

The other group is represented by birds with a very small moult gap in the primaries or with a very low primary moult score, indicating that primary moult will probably suspended until arrival at the wintering grounds. 

Tables & Graph

remaining SPRING

 

 

 

 

 

 

 

starting date:

 30 Apr

 07 May

14 May

21 May

04 Jun

11 Jun

30 Jul

week no:

18

19

20

21

23

24

31

0

0

0

0

0

 

 

0

1

0

0

0

0

 

 

0

2

0

0

0

0

 

 

1

3

0

0

0

0

 

 

1

4

0

0

0

0

 

 

37

5

0

0

0

0

 

 

22

6

0

0

0

0

 

 

3

7

3

2

1

2

 

 

0

8

16

22

26

18

1

1

0

9

30

13

16

10

1

 

0

10

66

33

37

10

 

 

0

 

 

 

 

 

 

 

 

n=

115

70

80

40

2

1

64

average REM P:

9.4

9.1

9.1

8.7

8.5

8.0

4.4

95% CID =

0.15

0.23

0.20

0.29

6.35

 

0.17

inverse =

1.98

1.99

1.99

2.02

12.71

 

2.00

Variantie (s2) =

0.68

0.90

0.84

0.83

0.50

 

0.46

SD (s) =

0.82

0.95

0.91

0.91

0.71

 

0.68

SE (sx) =

0.08

0.11

0.10

0.14

0.50

 

0.09

 

 

 

 

 

 

 

 

% class:

 

 

 

 

 

 

 

0

0

0

0

0

0

0

0

1

0

0

0

0

0

0

0

2

0

0

0

0

0

0

2

3

0

0

0

0

0

0

2

4

0

0

0

0

0

0

58

5

0

0

0

0

0

0

34

6

0

0

0

0

0

0

5

7

3

3

1

5

0

0

0

8

14

31

33

45

50

100

0

9

26

19

20

25

50

0

0

10

57

47

46

25

0

0

0

 

 

 

 

 

 

 

 

% control:

100

100

100

100

100

100

100

  Table above, data for the Netherlands (2000-2010), results for spring & summer (aggregated week): number of remaining old primaries in adults.
0 = 0 old primaries left (P10 dropped); 10 = all 10 primaries still old and present.

Above: Scatter Plot for PMS in adult Herring Gulls. Number of remaining old primaries throughout the year. Sample size is 1.329 birds.

new: SPRING

 

 

 

 

starting date:

 30 Apr

07 May 

14 May 

21 May 

week no:

18

19

20

21

0

104

60

66

30

1

7

9

12

7

2

4

1

2

3

3

0

0

0

0

4

0

0

0

0

5

0

0

0

0

6

0

0

0

0

7

0

0

0

0

8

0

0

0

0

9

0

0

0

0

10

0

0

0

0

 

 

 

 

 

n=

115

70

80

40

average NEW P:

0.1

0.2

0.2

0.3

95% CID =

0.08

0.10

0.10

0.20

inverse =

1.98

1.99

1.99

2.02

Variantie (s2) =

0.18

0.16

0.21

0.38

SD (s) =

0.43

0.40

0.46

0.62

SE (sx) =

0.04

0.05

0.05

0.10

 

 

 

 

 

% class:

 

 

 

 

0

90

86

83

75

1

6

13

15

18

2

3

1

3

8

3

0

0

0

0

4

0

0

0

0

5

0

0

0

0

6

0

0

0

0

7

0

0

0

0

8

0

0

0

0

9

0

0

0

0

10

0

0

0

0

 

 

 

 

 

% control:

100

100

100

100

  Table above, data for the Netherlands (2000-2010), results for spring & summer (aggregated week): number of new, fully grown primaries in adults.
0 = no new primaries visible. So either P1 still old, or P1 dropped, but the very tip still not visible.
1 = P1 longest new primary. Range between "at least the tip of P1 is visible" until "tip of P2 still shorter than P1".
2 = P2 longest new primary. 3 = etc.

Above: Scatter Plot for PMS in adult Herring Gulls throughout the year. Longest new primary is classified "fully grown". Sample size is 3.271 birds. Birds scored on NEW primaries.

The first date in our analysis on adult Herring Gulls is 02 May 2006 (week 18 - starting 30 April), on which we already found birds with missing primaries (some birds had already shed 3 primaries). This group of actively moulting birds, 43% of the sample, must have started the complete moult somewhere around mid-April and probably several birds may have started earlier.

The last scoring day has been 03 December, when still 20% of the sampled birds had to grow P10. The final stage of the complete moult for all birds has to be somewhere after mid-December. On 03 December we scored 59 birds with P10 fully grown, 13 birds with P9 fully grown and 2 birds with P8 fully grown. They all had no old primaries left.

The first time a new primary (P1) was visible, was also on 02 May 2006 (week 18 - starting 30 April). In this week, 90% of the sample did not show new primaries, but 9% did. Four birds in the sample of 115 birds alreday had P2 as longest primary (fully grown). As soon as the tip of P1 was visible, this was automatically scored "fully grown", and this was the case in 7 birds. For the other primaries to be scored fully grown, they had to exceed the previous primary in length (so P2 fully grown, only from when it is longer than P1).

LINEAR REGRESSION

Onset of primary moult can best be illustrated by a sinusoid for the first few weeks and last weeks, but there appears to be linear dependency over much of the central moult period.

LINEAR REGRESSION FOR OLD REMAINING PRIMARIES

Complete sample: Linear regression (n = 1329, R2= 0.935, sign: P<0,000)
PMS = -0,379* WEEK + 16,324.

LINEAR REGRESSION FOR NEW FULLY GROWN PRIMARIES

Complete sample: Linear regression (n = 3271 R2= 0.927, sign: P<0,000)
PMS = 0,322* WEEK - 6,071.

rings argenteus: UK.
2cy argenteus in March, ringed in France. (57822 bytes)Herring Gull (argenteus) adult PS1.T May 2012 & April 2013, Boulogne-sur-Mer, NW France. Picture: Jean-Michel Sauvage.
rings argenteus: France
2cy argenteus in March, ringed in France. (57822 bytes)Herring Gull MAA adult (argenteus), April-May 2012, Boulogne/Mer, France (50.42N,1.34E). Picture: J-M Sauvage.
adult argenteus in April, ringed in France.Herring Gull DA254408 5cy (argenteus), April 29 2012, Boulogne/Mer, France (50.42N,1.34E). Picture: J-M Sauvage.
adult argenteus in April, ringed in France.Herring Gull DA205992 adult (argenteus), April 07 2004, Nieuwland - Sloe, the Netherlands. Picture Pim Wolf.
rings argenteus: Belgium
2cy argenteus in March, ringed in France. (57822 bytes)Herring Gull CPAX 2-5cy (argenteus), 2009-2012, Boulogne/Mer, France. Picture: J-M Sauvage.
2cy argenteus in March, ringed in France. (57822 bytes)Herring Gull GDAV 5-6cy (argenteus), March 2011 & April 2012, Boulogne/Mer, France. Picture: J-M Sauvage.
adult argenteus in April, ringed in Belgium. (85360 bytes)Herring Gull H-113492 adult (argenteus), April 13 2004, Dintelhaven - Maasvlakte, the Netherlands (51.59N 04.02E)
adult argenteus in April, ringed in Belgium.Herring Gull H-127209 adult (argenteus), April 06 2004, Nieuwland - Sloe, the Netherlands. Picture Pim Wolf.
adult argenteus in October, ringed in the Netherlands. (35116 bytes)Herring Gull H-128166 adult (argenteus), April 19 2008, Boulogne/Mer, France (50.42N,1.34E). Picture: J-M Sauvage.
adult argenteus in October, ringed in the Netherlands. (35116 bytes)Herring Gull H-132860 adult (argenteus), April-July 19 2012, Calais, France. Picture: J-M Sauvage.
adult argenteus in April, ringed in Belgium.Herring Gull H-145461 adult (argenteus), April 08 2011, Maasvlakte, the Netherlands. Picture Evert Eijkelenboom.
adult argenteus in October, ringed in the Netherlands. (35116 bytes)Herring Gull H-88093 18-19cy (argenteus), 2010-2012, IJmuiden, the Netherlands.
rings argenteus: the Netherlands
1cy argenteus in August, ringed in Belgium. (90559 bytes)Herring Gull KNAT 8+cy (argenteus), 2010-2011, Leiden, the Netherlands.
2cy argenteus in March, ringed in France. (57822 bytes)Herring Gull DA 24-27cy (argenteus, 2009-2010, Leiden, Netherlands.
adult argenteus in April, ringed in the Netherlands. (73053 bytes)Herring Gull P-  adult (argenteus), April 05 2003, Brouwersdam, the Netherlands (51.45N-03.52E).
adult argenteus in April, ringed in Belgium.Herring Gull 6S adult (argenteus), April 08 2011, Maasvlakte, the Netherlands. Picture Evert Eijkelenboom.
adult argenteus in April, ringed in Belgium.Herring Gull 08 adult (argenteus), April 08 2011, Maasvlakte, the Netherlands. Picture E Eijkelenboom & M v Kleinwee.
adult argenteus in April, ringed in Belgium.Herring Gull K4 adult (argenteus), April 08 2011, Maasvlakte, the Netherlands. Picture Evert Eijkelenboom.
adult argenteus in April, ringed in Belgium.Herring Gull LJ and LH adult (argenteus), April 08 2011, Maasvlakte, the Netherlands. Picture Evert Eijkelenboom.
adult argenteus in April, ringed in the Netherlands. (79121 bytes)Herring Gull 5.277.846 13cy (argenteus), April 02 2004, IJmuiden, the Netherlands (52.27N 04.33E). 
adult argenteus in April, ringed in the Netherlands.Herring Gull 5.36?.103 adult (argenteus), April 15 2001, IJmuiden, the Netherlands (52.27N 04.33E). 
2cy argenteus in March, ringed in France. (57822 bytes)Herring Gull 5.419.235 5cy (argenteus), 2010-2011, Leiden, Netherlands.
sub-adult argenteus in April, ringed in the Netherlands. (60988 bytes)Herring Gull E 5cy (argenteus), April 25 2003, Scheveningen, the Netherlands.
rings argentatus: Finland
3cy argentatus in January. (80207 bytes)Herring Gull argentatus C0E19 adult, March 21 2014, Pori, Finland. Picture: Petteri Mäkelä.
3cy argentatus in January. (80207 bytes)Herring Gull argentatus CA56L adult, April 04 2014, Pori, Finland. Picture: Petteri Mäkelä.
unringed adult Herring Gulls
3cy argentatus in January. (80207 bytes)Herring Gull argentatus adult, April 10 2014, Pori, Finland. Picture: Petteri Mäkelä.
3cy argentatus in January. (80207 bytes)Herring Gull argentatus adult, April 10 2014, Pori, Finland. Picture: Petteri Mäkelä.
3cy argentatus in January. (80207 bytes)Herring Gull argentatus adult, April 10 2014, Pori, Finland. Picture: Petteri Mäkelä.
3cy argentatus in January. (80207 bytes)Herring Gull argentatus adult, April 04 2014, Pori, Finland. Picture: Petteri Mäkelä.
3cy argentatus in January. (80207 bytes)Herring Gull argentatus adult, April 04 2014, Pori, Finland. Picture: Petteri Mäkelä.
3cy argentatus in January. (80207 bytes)Herring Gull argentatus adult, April 04 2014, Pori, Finland. Picture: Petteri Mäkelä.
3cy argentatus in January. (80207 bytes)Herring Gull argentatus adult, April 04 2014, Pori, Finland. Picture: Petteri Mäkelä.
3cy argentatus in January. (80207 bytes)Herring Gull argentatus adult, April 04 2014, Pori, Finland. Picture: Petteri Mäkelä.
3cy argentatus in January. (80207 bytes)Herring Gull argentatus adult, April 04 2014, Pori, Finland. Picture: Petteri Mäkelä.
3cy argentatus in January. (80207 bytes)Herring Gull argentatus adult, April 04 2014, Pori, Finland. Picture: Petteri Mäkelä.
3cy argentatus in January. (80207 bytes)Herring Gull argentatus adult, April 04 2014, Pori, Finland. Picture: Petteri Mäkelä.
3cy argentatus in January. (80207 bytes)Herring Gull argentatus adult, April 04 2014, Pori, Finland. Picture: Petteri Mäkelä.
3cy argentatus in January. (80207 bytes)Herring Gull adult, April 09 2014, Katwijk, the Netherlands.
3cy argentatus in January. (80207 bytes)Herring Gull adult, April 09 2014, Katwijk, the Netherlands.
3cy argentatus in January. (80207 bytes)Herring Gull adult, April 09 2014, Katwijk, the Netherlands.
3cy argentatus in January. (80207 bytes)Herring Gull adult, April 09 2014, Katwijk, the Netherlands.
3cy argentatus in January. (80207 bytes)Herring Gull adult, April 09 2014, Katwijk, the Netherlands.
3cy argentatus in January. (80207 bytes)Herring Gull adult (argenteus), April 17 2012, Noordwijk, the Netherlands.
3cy argentatus in January. (80207 bytes)Herring Gull adult (argenteus), April 17 2012, Noordwijk, the Netherlands.
3cy argentatus in January. (80207 bytes)Herring Gull adult, April 09 2014, Katwijk, the Netherlands.
3cy argentatus in January. (80207 bytes)Herring Gull adult, April 09 2014, Katwijk, the Netherlands.
3cy argentatus in January. (80207 bytes)Herring Gull adult, April 09 2014, Katwijk, the Netherlands.
3cy argentatus in January. (80207 bytes)Herring Gull adult, April 09 2014, Katwijk, the Netherlands.
3cy argentatus in January. (80207 bytes)Herring Gull adult, April 09 2014, Katwijk, the Netherlands.
3cy argentatus in January. (80207 bytes)Herring Gull adult, April 09 2014, Katwijk, the Netherlands.
3cy argentatus in January. (80207 bytes)Herring Gull adult, April 09 2014, Katwijk, the Netherlands.
3cy argentatus in January. (80207 bytes)Herring Gull adult, April 09 2014, Katwijk, the Netherlands.
3cy argentatus in January. (80207 bytes)Herring Gull adult, April 09 2014, Katwijk, the Netherlands.
3cy argentatus in January. (80207 bytes)Herring Gull adult, April 09 2014, Katwijk, the Netherlands.
3cy argentatus in January. (80207 bytes)Herring Gull adult, April 09 2014, Katwijk, the Netherlands.
3cy argentatus in January. (80207 bytes)Herring Gull adult, April 11 2014, Katwijk, the Netherlands.
adult argenteus in April.Herring Gull adult (argenteus), April 15 2001, IJmuiden, the Netherlands (52.27N 04.33E). Male and female.
adult argenteus in April.Herring Gull adult (argenteus), April 15 2001, IJmuiden, the Netherlands (52.27N 04.33E).
adult argenteus in April.Herring Gull adult (argenteus), April 15 2001, IJmuiden, the Netherlands (52.27N-04.33E).
adult argenteus in April.Herring Gull adult (argenteus), April 15 2001, IJmuiden, the Netherlands (52.27N 04.33E). Female left, male right.
adult argenteus in April.Herring Gull adult (argenteus), April 15 2001, IJmuiden, the Netherlands (52.27N 04.33E). Note missing feathers around the eye.
adult argenteus in April. (47433 bytes)Herring Gull adult (argenteus), April 02 2004, IJmuiden, the Netherlands (52.27N 04.33E). Note the speckling in the iris.