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
Red and Black on the Bill
Scores for black and red markings on the bill are shown in table 6; some example Herring Gulls showing patterns of red are shown in plate 4. In Herring Gulls, red on the upper mandible was found on 10 females (3.5% of our sample), but not on any males, and this sex difference was significant (Pearson χ20.05,1 = 12.013, P = 0.001, male n = 147, female n = 117).
Over half (61%) of the Lesser Black-backed Gulls had red on the upper mandible, with females more frequently showing red than males (Pearson χ20.05,1 = 69.643, P = 0.000, male n = 434, female n = 492).
Black markings on the bill were found more frequently in male than in female Herring Gulls (table 6). The frequency of black in Herring Gulls did not differ significantly between the sexes for both upper mandible (Pearson χ2 = 0.125, P = 0.723, male n = 147, female n = 127) and lower mandible (Pearson χ2 = 3.763, P = 0.052, male n = 147, female n = 126).
28% of the breeding Herring Gulls showed black on both mandibles. The sex difference for black on both mandibles was not significant: Pearson χ2 = 1.156, P = 0.282, male n = 147, female n = 126. Sub-adult Herring Gulls, i.e. birds with black on the primary coverts, more frequently show black on both mandibles (Mann-Whitney U = 1822, Z = -2.997, P = 0.003, adult n = 251, sub-adult n = 21). When these sub-adult birds are excluded, the sex difference for black on both mandibles remains non-significant: Pearson χ2 = 0.780, P = 0.373, male n = 92, female n = 93).
 "Top of the bill": red on the upper mandible in LBBG o4H. |
In Lesser Black-backed Gulls, 63% of all breeding birds had black on both mandibles. Black on the bill was found more frequently in females (table 6). The difference between the sexes in the frequency of black was significant for both upper mandible (Pearson χ2 = 12.802, P = 0.000, male n = 435, female n = 492) and lower mandible (Pearson χ2 = 17.758, P = 0.000, male n = 433, female n = 491).
When sub-adult Lesser Black-backed Gulls (immature markings on the primary coverts) are excluded, 62% showed black on both mandibles. The difference between sexes in red and black markings remains significant when sub-adults are excluded from the sample (red on upper mandible, sub-adults excluded: Pearson χ2 = 70638, Z = -7.276, P = 0.000, male n = 391, female n = 475; black on both mandibles, sub-adults excluded: Pearson χ2 = 79572, Z = -4.176, P = 0.000, male n = 390, female n = 474).
|
red on upper mandible
|
black on upper mandible
|
black on lower mandible
|
|||||||
|
no
|
yes
|
total
|
no
|
yes
|
total
|
no
|
yes
|
total
|
|
| HG ♂ |
54
|
-
|
54
|
30
|
23
|
54
|
27
|
26
|
54
|
| HG ♀ |
43
|
4
|
46
|
25
|
21
|
46
|
29
|
17
|
46
|
| total |
96
|
4
|
100
|
55
|
45
|
100
|
56
|
44
|
100
|
| LBBG ♂ |
25
|
22
|
47
|
7
|
41
|
47
|
12
|
35
|
47
|
| LBBG ♀ |
14
|
39
|
53
|
12
|
41
|
53
|
20
|
33
|
53
|
| total |
39
|
61
|
100
|
19
|
81
|
100
|
32
|
68
|
100
|
Table 6. Bill markings in breeding Herring & Lesser Black-backed Gulls at Moerdijk in 2005 & 2006. Values are %. In Herring Gull: red on bill n = 274, black on upper mandible n = 274 and on lower mandible n = 273. In Lesser Black-backed Gull: red n = 926, for black on upper mandible n = 927 and lower mandible n = 924.
Plate 4. Some example Herring Gulls scored negative (left) and positive (right) for red on the upper mandible.
Read further on RESULTS: 8 IRIS SPECKLING & ORBITAL RING COLOUR >
Lesser Black-backed Gull L.f. graellsii 14cy female ST, 21 May 2005. No red on um, black on um and lm.
Herring Gull L.a. argenteus 17cy female 1A, 04 May 2005. Red on um, black on um and lm.
Lesser Black-backed Gull L.f. graellsii 14cy female UX, 15 May 2006. No red on um, black on um and lm.
Herring Gull L.a. argenteus female 6J, 21 May 2005. Red on um, black on um, but not on lm.
Lesser Black-backed Gull L.f. graellsii 14cy female C5, 08 May 2006. No red on um, black on um and lm.
Herring Gull L.a. argenteus female 6P, 21 May 2005 & 08 May 2006. Red on um, no black on bill.
Lesser Black-backed Gull L.f. graellsii 12cy female 65, 09 May 2006. Red on um, much black on um and on lm.
Herring Gull L.a. argenteus female 6V, 21 May 2005. Red on um, no black on bill.
Lesser Black-backed Gull L.f. graellsii 12cy male P8, 16 May 2006. No red on um, black on um and lm.
Herring Gull L.a. argenteus female UT, 21 May 2005. Red on um, no black on bill.
Lesser Black-backed Gull L.f. graellsii 11cy female LA, 16 May 2005. No red on um, black on um and lm.
Herring Gull L.a. argenteus female 2H, 05 May 2005 & 16 May 2006. Red on um, black on um and lm.
Lesser Black-backed Gull L.f. graellsii 10cy male BX, 06 May 2005. No red on um, black on um and no black on lm.
Herring Gull L.a. argenteus female A8, 06 May 2005 & 16 May 2006. Red on um, no black on bill.
Lesser Black-backed Gull L.f. graellsii 8cy male E6, 04 May 2006. No red on um, black on um and no black on lm.
Herring Gull L.a. argenteus female E9, 04 May 2006. Red on um, black on um and lm.
Lesser Black-backed Gull L.f. graellsii 5cy male E0, 14 May 2006. No red on um, black on um and on lm.
Herring Gull L.a. argenteus female HJ, 04 May 2006. Red on um, black on lm, but not on um.
Lesser Black-backed Gull L.f. graellsii 4cy male HZ, 14 May 2006. No red on um, black on um and on lm.
Herring Gull L.a. argenteus female K3, 09 May 2006. Red on um, no black on the bill.
Lesser Black-backed Gull L.f. graellsii 4cy male BA, 02 May 2006. No red on um, black on um and on lm.
Herring Gull L.a. argenteus female K7, 09 May 2006. Red on um, no black on the bill.
Lesser Black-backed Gull L.f. graellsii 13cy female T4, 21 May 2005. Red on um, no black on um or lm.
Herring Gull L.a. argenteus female PN, 07 May 2006. Red on um, no black on the bill.
Lesser Black-backed Gull L.f. graellsii 13cy female CK, 06 May 2005. Red on um, black on um and lm.
Herring Gull L.a. argenteus 4cy E4, 02 May 2006. No red on um, black on um and lm.
Lesser Black-backed Gull L.f. graellsii 12cy male ET, 04 May 2006. Red on um, black on um and on lm.
Herring Gull L.a. argenteus male 4cy-5cy 6T, 21 May 2005 & 09 May 2006. No red on um, black on um and lm.
Lesser Black-backed Gull L.f. graellsii 11cy male K9, 16 May 2005. Red on um, black on um and on lm.
Herring Gull L.a. argenteus female 5cy HK, 04 May 2006. No red on um, black on um and lm.
Lesser Black-backed Gull L.f. graellsii 11cy male EX, 14 May 2005. Red on um, black on um and on lm.
Herring Gull L.a. argenteus male 5cy HT, 05 May 2006. No red on um, black on um and lm.
Lesser Black-backed Gull L.f. graellsii 11cy female AZ, 05 May 2005. Red on um, no black on um or lm.
Herring Gull L.a. argenteus male 5cy J2, 05 May 2006. No red on um, black on um and lm.
Lesser Black-backed Gull L.f. graellsii 11cy female 9K, 09 May 2006. Red on um, black on um and on lm.
Herring Gull L.a. argenteus male 5cy NU, 23 May 2006. No red on um, black on um and lm.
Lesser Black-backed Gull L.f. graellsii 11cy female 68, 09 May 2006. Red on um, black on um and on lm.
Herring Gull L.a. argenteus male 6cy J7, 09 May 2006. No red on um, black on um and lm.
Lesser Black-backed Gull L.f. graellsii 10cy male 9U, 05 May 2005. Red on um, black on um and no black on lm.
Herring Gull L.a. argenteus male 6cy K4, 09 May 2006. No red on um, black on um and lm.
Lesser Black-backed Gull L.f. graellsii 10cy female 0U, 05 May 2005. Red on um, black on um and lm.
Herring Gull L.a. argenteus male 7cy 18, 05 May 2005. No red on um, black on um and lm.
Lesser Black-backed Gull L.f. graellsii 8cy male 14, 04 May 2005. Red on um, black on um and lm.
Herring Gull L.a. argenteus male 9cy P3, 16 May 2005. No red on um, black on um and lm.
Lesser Black-backed Gull L.f. graellsii 8cy male VH, 08 May 2006. Red on um, black on um and lm.
Herring Gull L.a. argenteus male 10cy KL, 09 May 2006. No red on um, black on um and lm.
Lesser Black-backed Gull L.f. graellsii 8cy male 3N, 06 May 2006. No red on um, black on um and on lm.
Herring Gull L.a. argenteus male 11cy H2, 05 May 2006. No red on um, black on um and lm.
Lesser Black-backed Gull L.f. graellsii 8cy male 6W, 08 May 2006. No red on um, no black on um or on lm.
Herring Gull L.a. argenteus female 14cy C0, 06 May 2005. No red on um, black on um and lm.
Lesser Black-backed Gull L.f. graellsii 5cy male 20, 06 May 2006. Red on um, black on um and on lm.