Gull Topography - about remiges & scapular coverts...

(last update: 10 oktober 2005)

Herring Gull argentatus
Herring Gull argenteus
Herring Gull smithsonianus
Great Black-backed Gull marinus
Lesser B-b Gull graellsii / intermedius
Lesser B-b Gull fuscus
Yellow-legged Gull michahellis
Yellow-legged Gull atlantis
Caspian Gull cachinnans
Armenian Gull armenicus
Baraba Gull barabensis
Heuglini's Gull heuglini
Vega Gull vegae
Mongolian Gull mongolicus
Slaty-backed Gull schistisagus
Black-headed Gull ridibundus 
Grey-headed Gull cirrocephalus 
Brown-headed Gull brunnicephalus 
Bonaparte's Gull philadelphia 
Little Gull minutus
Mediterranean Gull melanocephalus
Relict Gull relictus
Audouin's Gull audouinii
Slender-billed Gull genei
Common / Mew Gull canus
Ring-billed Gull delawarensis
Franklin's Gull pipixcan
Laughing Gull atricilla
Kittiwake Rissa tridactyla
Ivory Gull Pagophila eburnea
Ross's Gull Rodosthetia rosea
Sabine's Gull sabini
Great Black-headed Gull ichtyaetus
Sooty Gull hemprichii
White-eyed Gull leucophthalmus
Glaucous Gull hyperboreus
Iceland Gull glaucoides
Thayer's Gull thayeri
Kumlien's Gull kumlieni
Mystery Gulls
Skua's Catharacta / Stercorarius
Terns Sterna
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Normally, during summer and autumn, gulls in the Netherlands moult the body feathers, tail feathers (rectrices) and flight feathers. The flight feathers (remiges) can be divided in two groups: secondaries and primaries. The primaries are moulted and numbered in descendant order (from body towards wing-tip), while the secondaries are moulted and numbered in ascendant order (from the outermost secondary to the innermost secondary). For convenience, we have treated the tertials as a separate group from the secondaries.
Duration of moult depends on species and may take up to 6 months.

In recent years, the study of moult score and moult strategy has increased. It is believed for instance that separating Lesser Black-backed Gull L.f.graellsii and L.f.intermedius from Baltic Gull L. f. fuscus should mainly be based on moult scores. The scores of moult of flight feathers is: score 0 for an old feather, score 1 for a lost or just growing new feather, score 2 when a feather is at one quarter, score 3 when a feather is at half of the length, score 4 at three-quarter, and score 5 when a feather is fully grown, lacking the waxy sheath. From April-July (start) to September-December (completion) the score increases from 0 to 50 in any single wing. Nevertheless, detailed descriptions remain necessary (and often mentioned at these pages) when moult is arrested, or strategies are complex and odd (e.g. P1-P5 new, P6-P7 old, P8-P10 new). Immature gulls start (and finish) the moult at an earlier date than adults.

In the picture below, a 2cy Yellow-legged Gull, show the main upper-part feathers. Note that the coverts are counted outwards: g1 being the innermost greater covert #1 and g15 being the 15th greater covert, often the last seen in a folded wing. The tertials are counted downwards: t1 to t6 where-after the merge into the secondaries. In the top picture, it can be seen that e.g. the scapulars are a relative large region of feathers. Therefore we use in the field a subdivision: upper scapulars and lower scapulars. Within the group of lower scapulars, three bars can be seen, upper lower scapulars, central lower scapulars and lower lower scapulars. And again, these can be divided in two groups: the inner and outer feathers. This makes exact allocation possible of single feathers. Note the second generation primaries with rounded tips.

Moult score (2cy in July): P1 halfway, P2 just visible, P3-P4 missing, P5-P10 old, primary moult score (PMS) = 7.

Moult score (adult intermedius in November): P1-P8 new, P9 growing at 25% and P10 missing, score is 42.

Remiges and rectrices in LBBG (Lesser Black-backed Gulls)

Here you find some examples of different generation flight-feathers (remiges) and tail-feathers (rectrices). Click the thumbnails to go the linked pages with full-screen images.

Juvenile LBBG in August. Primaries and secondaries are all juvenile, i.e. fresh first generation remiges. Juvenile LBBG in September. All tail-feathers (rectrices) are still juvenile, i.e. fresh first generation rectrices.

2cy LBBG in August. All visible flight-feathers are new second generation remiges. Note the white tips of the secondaries. Outer primaries are still growing.

2cy LBBG in August. Complete tail is renewed and now fresh second generation rectrices with a white fringe.

3cy LBBG in June. Old second generation remiges with worn tips and bleached centres.

3cy LBBG in June. Complete tail consist of old second generation rectrices creating a broad black tail-band.
3cy LBBG in September. The inner primaries are fresh third generation remiges, with a grey base, white tips and sub-terminal black markings from p3 onwards. P9 and p10 are still old 2nd generation primaries. 3cy LBBG in June. New third generation rectrices in June are predominantly white but may also show some isolated black spots near the centre. New rectrices, combined with old remiges.
Adult LBBG in June. All old adult remiges are about half a year of age and the old tips are worn. 9cy adult LBBG in April. The adult rectrices and remiges are half a year of age. The tail is all-white of course.