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
Commencement of primary moult
The timing of primary moult varies geographically in the argentatus-fuscus-complex. To place the Moerdijk colony in a broader perspective we also include timing of moult commencement. On 02 May (2006), the earliest day of fieldwork in the colony, four of the seven trapped Herring Gulls had commenced their complete moult. Two of these breeding birds probably started the complete moult already in late April, as they had both P1 and P2 missing by early May. The 21 May (2005) was the last date we trapped Herring Gulls. Ten out of 37 birds still hadn’t commenced the primary moult. Most Herring Gulls started moult in May: in the first half of May 46% (n = 211), and in the second half of May, 65% (n = 94) of the birds was in active primary moult.
We caught 48 Lesser Black-backed Gulls on 02 May (2006), with seven birds showing active primary moult. The latest project day was 10 June (2006). On this date, eight Lesser Black-backed Gulls were caught and six of these had not commenced primary moult. Only a minority of breeding Lesser Black-backed Gulls started moult in May: in the first half of May 6% (n = 747), and in the second half of May, 33% (n = 257) of the birds was in active primary moult.
In our sample, the highest primary moult score (PMS) attained by a Herring Gull was 11, found in bird mSL on 21 May 2005 (P1-P2 fully grown, P3 missing). 17 Lesser Black-backed Gulls returned into the colony with arrested primary moult: fresh, fully grown primaries moulted in on the wintering grounds (see plate 9). We found 13 Lesser Black backed Gulls that had replaced P1, and four that had replaced both P1 and P2. None of these birds was in active moult at the time it was caught on the nest, and for this reason those birds were excluded from figure 3.
Figure 3: PMS. Primary Moult Scores in May for actively moulting Herring Gulls (top boxplot; n = 160, out of 314 birds) and Lesser Black-backed Gulls (bottom boxplot; n = 187, out of 997 birds). 01 May = day 1. o: Outliers. *: Extremes. Numbers of actively moulting birds in % along X-axis.
LBBG showing arrested moult not in this figure, for they are not in ‘active moult’.
On day 23, 11 LBBG were all scored PMS0 (no active moult).
Click HERE for larger boxplots / figure 3.
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Lesser Black-backed Gull L.f. graellsii 12cy AF, 02 May 2006. P1 new & P2 old, PMS value = 5.
Herring Gull L.a. argenteus male E3, 02 May 2006. Early moulting bird with PMS value = 1 (P1 dropped).
Lesser Black-backed Gull L.f. graellsii 12cy A4, 02 May 2006. P1 new & P2 old, PMS value = 5.
Herring Gull L.a. argenteus female E5, 02 May 2006. Early moulting bird with PMS value = 1 (P1 dropped).
Lesser Black-backed Gull L.f. graellsii 12cy B7, 02 May 2006. P1 new & P2 old, PMS value = 5.
Herring Gull L.a. argenteus male SL, 21 May 2005. Highest PMS value in Herring Gulls = 11.
Lesser Black-backed Gull L.f. graellsii 12cy BM, 02 May 2006. P1 new & P2 old, PMS value = 5.
Herring Gull L.a. argenteus 8cy 2Z, 06 May 2005. PMS value = 10. P1 fully grown, P2 almost, P3 missing.
Lesser Black-backed Gull L.f. graellsii 62, 04 May 2005. P1 new & P2 old, PMS value = 5.
Lesser Black-backed Gull L.f. graellsii CJ, 06 May 2005. P1 new & P2 old, PMS value = 5.
Herring Gull L.a. argenteus female V0, 21 May 2005. May 21 is latest day PMS value = 0 (all primaries old).
Lesser Black-backed Gull L.f. graellsii 9cy NL, 13 May 2006. P1 new & P2 old, PMS value = 5.
Herring Gull L.a. argenteus female UT, 21 May 2005. May 21 is latest day PMS value = 0 (all primaries old).
Lesser Black-backed Gull L.f. graellsii 12cy L1, 13 May 2006. P1 new & P2 old, PMS value = 5.
Herring Gull L.a. argenteus adult 61, 21 May 2005 & 08 May 2006. May 21 is latest day PMS value = 0 (all primaries old).
Lesser Black-backed Gull L.f. graellsii HU, 14 May 2005. P1 new & P2 old, PMS value = 5.
Lesser Black-backed Gull L.f. graellsii LU, 16 May 2005. P1 new & P2 old, PMS value = 5.
Lesser Black-backed Gull L.f. graellsii M9, 13 May 2006. P1 missing & P2 very old, PMS value = 1.
Lesser Black-backed Gull L.f. graellsii RL, 16 May 2006. P1 new & P2 old, PMS value = 5.
Lesser Black-backed Gull L.f. graellsii JS, 05 May 2006. P1 growing & P2 very old, PMS value = 2.
Lesser Black-backed Gull L.f. graellsii S6, 21 May 2005. P1 new & P2 old, PMS value = 5.
Lesser Black-backed Gull L.f. graellsii LV, 16 May 2005. P5 short, PMS value = 0.
Lesser Black-backed Gull L.f. graellsii TJ, 21 May 2005. P1 new & P2 old, PMS value = 5.
Lesser Black-backed Gull L.f. graellsii CJ, 04 May 2006. P1 old, PMS value = 0.
Lesser Black-backed Gull L.f. graellsii 4cy BA, 02 May 2006. P1-P2 new & P3 old, PMS value = 10.
Lesser Black-backed Gull L.f. graellsii ET, 06 May 2005. P1 old, PMS value = 0.
Lesser Black-backed Gull L.f. graellsii CH, 06 May 2005. P1-P2 new & P3 old, PMS value = 10.
Lesser Black-backed Gull L.f. graellsii 45, 08 May 2006. P1 old, PMS value = 0.
Lesser Black-backed Gull L.f. graellsii EZ, 14 May 2005. P1-P2 new & P3 old, PMS value = 10.
Lesser Black-backed Gull L.f. graellsii P2, 05 May 2005. P1-P2 short. PMS value = 0.
Lesser Black-backed Gull L.f. graellsii L6, 16 May 2005. P1-P2 new & P3 old, PMS value = 10.
Lesser Black-backed Gull L.f. graellsii 9U, 09 May 2006. P1 old, PMS value = 0.
Lesser Black-backed Gull L.f. graellsii JX, 14 May 2005 & 26 March 2006. P1 old, PMS value = 0.
Lesser Black-backed Gull L.f. graellsii AR, 02 May 2006. P1 dropped, PMS value = 1.
Lesser Black-backed Gull L.f. graellsii 78, 09 May 2006. P1-P2 old, PMS value = 0.
Lesser Black-backed Gull L.f. graellsii B0, 02 May 2006. P1 dropped, PMS value = 1.
Lesser Black-backed Gull L.f. graellsii LN, 16 May 2006. P1-P2 old, PMS value = 0.
Lesser Black-backed Gull L.f. graellsii B5, 02 May 2006. P1 dropped, PMS value = 1.
Lesser Black-backed Gull L.f. graellsii LW, 16 May 2006. P1-P2 old, PMS value = 0.
Lesser Black-backed Gull L.f. graellsii NH, 16 May 2005. P1 growing, P2-P3 dropped, PMS value = 4.
Lesser Black-backed Gull L.f. graellsii BR, 03 May 2006. P1-P2 old, PMS value = 0.
Lesser Black-backed Gull L.f. graellsii MT, 13 May 2006. P1 old, PMS value = 0.