Moerdijk Field Research 2005-2006
(last update: 14 August 2010)
Roland-Jan Buijs
Theo Muusse
Mars Muusse
Introduction
Methods
Age, origin & sex
Retrapped Birds
Upperparts Greytone
Black on Primary Coverts
Black on Primaries
P10 and P9 Patterns
P5 Pattern
Red & Black on Bill
Iris & Orbital Ring
Primary Moult
Discussion
References
Number of Primaries with Black Pigmentation
On average, Herring Gulls breeding at Moerdijk had 5.9 primaries with black pigmentation (SD 0.51, n = 287; table 3), and sexes differed significantly (Mann-Whitney U = 8163, Z = -2.448, P = 0.014, male n = 147, female n = 128). The presence of black is age-related (but not significantly) in Herring Gull, with younger birds having more primaries with black pigmentation (b=-0.018, r2=0.028, P=0.351, n = 33 in known-age Herring Gulls).
When sub-adult birds (birds with dark on the primary coverts) are excluded from the analysis, the difference between sexes remains significant (Mann-Whitney U = 8105, Z = -2.339, P = 0.019, male n = 145, female n = 128).
The average number of primaries with black pigmentation in Lesser Black-backed Gull was 6.9 (SD 0.61, n = 931), and the sex difference was just significant (Mann-Whitney U = 100938, Z = -1.992, P = 0.046, male n = 433, female n = 498). In Lesser Black-backed Gull too, the number of primaries with black is age-related, when sub-adults are compared to known-age adults (sub-adults: mean 7.2, SD 0.68; adults: mean 6.7, SD 0.64, Mann-Whitney U = 1000, Z = -4.071, P < 0.001, sub-adult n = 62, adult n = 53. See table 4). However, we found some exceptions, as older birds like 10cy LBBG o67, 12cy LBBG yET, 12cy LBBG o65 showed 8 and even 9 primaries with black. When sub-adults (62 birds, of which 70% are males) are excluded from the analysis, the difference between the sexes is no longer significant (Mann-Whitney U = 89591, Z = -1.294, P = 0.196, male n = 390, female n = 480).
|
Number of primaries with black
|
Total
|
||||||
|
5
|
6
|
7
|
8
|
9
|
|
||
| HG ♂ |
7
|
40
|
6
|
.
|
.
|
53
|
|
| HG ♀ |
11
|
33
|
3
|
.
|
.
|
47
|
|
| total |
17
|
73
|
9
|
.
|
.
|
100
|
|
| LBBG ♂ |
.
|
10
|
30
|
6
|
1
|
47
|
|
| LBBG ♀ |
0
|
13
|
35
|
5
|
0
|
53
|
|
| total |
0
|
23
|
65
|
11
|
1
|
100
|
|
Table 3: Number of primaries with black pigmentation in Herring and Lesser Black-backed Gulls. Values are %.
| Number of primaries with black - in known age LBBG | ||||||||||||
|
4cy
|
5cy
|
6cy
|
7cy
|
8cy
|
9cy
|
10cy
|
11cy
|
12cy
|
13cy
|
14cy
|
total
|
|
|
6
|
0
|
3
|
2
|
4
|
6
|
0
|
2
|
2
|
1
|
2
|
1
|
23
|
|
7
|
6
|
1
|
3
|
3
|
8
|
4
|
4
|
4
|
2
|
1
|
2
|
38
|
|
8
|
6
|
3
|
0
|
0
|
0
|
0
|
1
|
0
|
1
|
0
|
0
|
11
|
|
9
|
1
|
1
|
0
|
0
|
0
|
0
|
0
|
0
|
1
|
0
|
0
|
3
|
|
total:
|
13
|
8
|
5
|
7
|
14
|
4
|
7
|
6
|
5
|
3
|
3
|
75
|
Table 4: Number of primaries with black pigmentation in Lesser Black-backed Gulls of known age (ringed as pullus).
Read further on RESULTS: 4. P9 & P10 PRIMARY PATTERNS >
Herring Gull L.a. argenteus 4cy-5cy 6T, 21 May 2005 & 09 May 2006. In 2005 P4-P10: seven primaries with black.
Herring Gull L.a. argenteus 5cy-6cy 13, 05 May 2005 & 09 May 2006. In 2005 P4-P10: seven primaries with black.
Herring Gull L.a. argenteus 9cy P3, 16 May 2005. P4-P10: seven primaries with black.
Herring Gull L.a. argenteus 4cy E4, 02 May 2006. P5-P10: six primaries with black.
Herring Gull L.a. argenteus 9cy LN, 13 May 2006. P5-P10: six primaries with black.
Herring Gull L.a. argenteus 11cy H2, 05 May 2006. P5-P10: six primaries with black.
Herring Gull L.a. argenteus 5cy HK, 04 May 2006. P6-P10: five primaries with black.
Herring Gull L.a. argenteus 10cy KL, 09 May 2006. P6-P10: five primaries with black.
Herring Gull L.a. argenteus 17cy 1A, 04 May 2005. P6-P10: five primaries with black.
Lesser Black-backed Gull L.f. graellsii sub-adult E0, 14 May 2006. P2-P10: nine primaries with black.
Lesser Black-backed Gull L.f. graellsii 12cy 65, 09 May 2006. P2-P10: nine primaries with black.
Lesser Black-backed Gull L.f. graellsii 10cy 67, 09 May 2006. P3-P10: eight primaries with black.
Lesser Black-backed Gull L.f. graellsii 12cy ET, 04 May 2006. P3-P10: eight primaries with black.
Lesser Black-backed Gull L.f. graellsii 8cy 14, 04 May 2005. P4-P10: seven primaries with black.
Lesser Black-backed Gull L.f. graellsii 11cy AZ, 05 May 2005. P4-P10: seven primaries with black.
Lesser Black-backed Gull L.f. graellsii sub-adult SZ, 21 May 2006. P5-P10: six primaries with black.
Lesser Black-backed Gull L.f. graellsii 8cy VH, 08 May 2006. P5-P10: six primaries with black.
Lesser Black-backed Gull L.f. graellsii 4W, 08 May 2006. Single bird scoring P6-P10: five primaries with black.