second
calendar year: August
Last update of
this page: 27-09-05 20:42
In Lesser Black-backed Gulls, nearly all feathers are being replaced by August. There may be
great differences, both between individual and in time: between the beginning and the end
of the month. Many birds change from a grabby immature into a fresh bird
with adult-like upper-parts and under-parts. From head to toe you can see
the following changes.
- The bill becomes paler.
Variation in bill colour is very obvious now. All-black bills (still
present in 20%) show pink bases while some birds (advanced) may show
a pink-yellow bill with only a small sub-terminal band. The average
birds show a pink bill with a dark distal half.
- The iris turns paler brown or whitish,
the advanced birds already show a yellowish white iris.
- The head varies from all-white without
any speckling or streaking to 'dirty' and heavily streaked on a grey
background.
- The under-parts moult into white feathers,
with dark streaks on the flank and at the sides of the breast. Quite
some birds show all-white worn under-parts by late August, with only some
streaking on the flanks.
- The mantle and scapulars consist of old
worn 2nd or 3rd generation feathers, being plain with a darker
shaft-streak and sub-terminal band, and fresh 3rd
or 4th generation feathers, being adult-like (though slightly paler than pure
adult-grey) and often with a darker shaft-streak or central
wedge.
- At the end of August, the majority of 2cy
LBBG
shows many 3rd generation mantle-feathers, creating a grey
triangle on the back.
- The differences in the amount of adult-grey
feathers on mantle/scapulars are obvious: some 2cy just have a few
grey feathers on the mantle while others have moulted all mantle and
scapulars into adult-like 3rd or 4th generation feathers.
- Most 2cy LBBGs still moult their mantle
and scapulars at the end of August (well into September), so the area
of grey on the upper-parts may still grow creating the grey saddle, as
often seen in 3cy birds returning in spring.
- Tertials on a 2cy LBBG in August
can exist of old juvenile as well as fresher 2nd generation
feathers or (for advanced birds) newly moulted 3rd
generation feathers. The juvenile tertials are very worn pale brown,
while 2nd generation feathers are all black with a broad
white tip (normally with a thumb-print pattern or vermiculation at the
sides). New 3rd
generation tertials are adult-like grey but may lack the obvious white
tip. By August, many birds miss at least some tertials, often the
upper tertials. When present, the upper tertials are normally the most
recently moulted ones.
- The wing-coverts are in active moult, so
gaps in the covert bars are very common. Normally, moult starts with
the median coverts. While moulting these medians, birds start to shed the greaters (and may shed the lessers as well). The inner median
coverts are normally moulted from the body to the outer-wing (up to #5
app.), while the
outer medians grow towards the body. Normally the meet at the 7th
or 8th median covert, counted from the body. The same
applies to the greater coverts, where moult normally starts with the
inner coverts. Wing covert moult ends with the outer
lesser coverts. Often, these feathers may be a clue for the age of a
bird.
- A common state of moult on a 2cy LBBG by
mid-August is:
new inner medians (2nd generation), a few new inner greaters (2nd
generation), missing outer and central greaters, missing at least the inner
half of the lessers and retained outer lessers. The 2nd
generation greater coverts are normally blackish with no or faint
barring. Second generation medians and lessers contrast with 1st generation feathers;
they are black centred with a whitish fringe or show barring or anchor
patterns.
- The primaries are moulted outwards and
at the end of August all present birds (n = 130) showed at least a fully grown p6. The average moult score
by the end of the
month is 40, with p7 fully grown, p8 half-way and p9 just visible. But
some birds scored 35, while some advanced individuals showed scores of
50. Compared to the old juvenile primaries, new primaries are darker
(jet black) and have a rounded top. The inner primaries are
paler than the outers, often p1 and p2 with a darker shaft on a brownish
background.
- The secondaries are shed inwards, from
the moment p5 is half way to fully grown, often creating large gaps
from p1 inwards. They are shed simultaneously (a few, about 5,
remain juvenile, and are visible as a block at approximately S5-10 and
S16-17).
Secondaries grow fast; birds with primary moult score 40 already have
at least 5 new secondaries, which are black centred.
- The under-wing becomes paler, as juvenile under-wing coverts are replaced by white or black-and-white
(contrasting) 2nd
generation feathers.
- The tail is 2nd generation in
many birds, still in active moult on some, but fully grown in many.
The new feathers are all-black or white with a broad irregular black
band. In many birds the 2nd generation tail shows more
black than on the juvenile. By November, some 2cy LBBGs show
predominantly white tail-feathers and probably some 2cy moulting the
tail-feathers in July are replacing 2nd generation feathers
for 3rd generation rectrices.
- Structurally, LBBGs show much individual
variation. One bird can easily be as large and robust as a Greater
Black-backed gull, while another (like female intermedius) is
only slightly larger than Common Gull (L.canus), gently built
with an attenuated rear.
- The more constant colour of the legs is
flesh-coloured to pink; only a very few have a hint of yellow.
- Those birds with advanced mantle and
scapulars may look like 3cy birds as they return in the Netherlands by
May next year.
Tables:
The tables below show primary scores of 2cy
LBBG in August. In the Netherlands, we have seen colour-ringed and
metal-ringed birds from British, Belgian, Dutch, German and Scandinavian
projects, thus from graellsii, intermedius and Dutch
intergrade populations. We therefore do not specify data to taxa
level.
2cy LBBG were identified on primary pattern ad upper-part coloration.
Primaries are scored fully-grown when a primary exceeds the previous
feather in the folded wing. Note that this also includes feathers which
would be scored 'just not fully grown' (score 4) in other researches. We
choose this score since it proved to be very difficult to establish the presence
of waxy sheath on the feather-base in field researches.
When judging the old primaries, be aware of the dark print on outer
primaries, created by the shed, previous feather. Such prints may contrast
strongly with the bleached primary tips.
2cy LBBG Maasvlakte - the Netherlands,
Aug 14 2003
|
new P |
p5 |
p6 |
p7 |
p8 |
p9 |
p10 |
n: |
P8 |
1 |
- |
- |
- |
- |
- |
1 |
P9 |
1 |
12 |
- |
- |
- |
- |
13 |
P10 |
- |
- |
7 |
- |
- |
- |
7 |
no old P |
- |
- |
9 |
2 |
- |
- |
11 |
n: |
2 |
12 |
16 |
2 |
- |
- |
32 |
notes:
n old primaries: 32
m old primaries: 1,1
SD old primaries: 0,94
95% CID old primaries: 0,34 |
n new primaries: 32
m new primaries:6,6
SD new primaries: 0,72
95% CID new primaries: 0,26
|
2cy LBBG
Westkapelle, the Netherlands, Aug 15 2003 |
new P |
p5 |
p6 |
p7 |
p8 |
p9 |
p10 |
n: |
P8 |
2 |
1 |
- |
- |
- |
- |
3 |
P9 |
- |
12 |
- |
- |
- |
- |
12 |
P10 |
- |
- |
22 |
- |
- |
- |
22 |
no old P |
- |
- |
3 |
3 |
- |
- |
6 |
n: |
2 |
13 |
25 |
3 |
- |
- |
43 |
notes:
n old primaries: 43
m old primaries: 1,3
SD old primaries: 0,80
95% CID old primaries: 0,25 |
n new primaries: 43
m new primaries: 6,7
SD new primaries: 0,68
95% CID new primaries: 0,21
|
2cy LBBG Maasvlakte - the Netherlands,
Aug 22 2002 |
new P |
P5 |
P6 |
P7 |
P8 |
P9 |
P10 |
n: |
P8 old |
2 |
2 |
- |
- |
- |
- |
4 |
P9 old |
- |
5 |
1 |
- |
- |
- |
6 |
P10 old |
- |
- |
25 |
2 |
- |
- |
27 |
no old |
- |
- |
12 |
16 |
1 |
- |
29 |
n: |
2 |
7 |
38 |
18 |
1 |
- |
66 |
notes:
n old primaries: 66
m old primaries: 0,8
SD old primaries: 0,86
95% CID old primaries: 0,21 |
n new primaries: 66
m new primaries: 7,1
SD new primaries: 0,74
95% CID new primaries: 0,18
|
2cy LBBG Maasvlakte - the Netherlands,
Sept 28
2001
|
new P |
P5 |
P6 |
P7 |
P8 |
P9 |
P10 |
n: |
. |
- |
- |
9 |
26 |
61 |
9 |
105 |
notes:
n new primaries: 105
m new primaries: 8,7
SD new primaries: 0,76
95% CID new primaries: 0,15 |
|
|
2cy LBBG: Dutch
intergrade
|
LBBG
L-x9892
2cy, August 15 2003, Westkapelle, the Netherlands. |
LBBG
L-901x95
2cy, August 29 2005, Westkapelle, the Netherlands. |
LBBG
A12E
2cy, August 14 2003, Naaktstrand, Maasvlakte, the Netherlands. |
LBBG
A82E
2cy, August 14 2003, Naaktstrand, Maasvlakte, the Netherlands. |
2cy
LBBG C95 E,
August 14 2004, Amsterdam, the Netherlands. A bird ringed left red C95,
right yellow E. |
LBBG IE
2cy, August 29 2003, IJmuiden, the Netherlands. |
2cy LBBG: intermedius
|
LBBG J93T
2cy, August 21 2003, IJmuiden, the Netherlands. |
LBBGJT74
2cy, August 21 2002, Cambridge, U.K. (52.14N 00.09E). Ringed in
Norway July 03 2001. |
2cy LBBG: unringed
birds
|
photo
7837: 2cy LBBG, August 15 2003, Westkapelle, the Netherlands. |
photo
7842: 2cy LBBG, August 15 2003, Westkapelle, the Netherlands. |
photo
7844: 2cy LBBG, August 15 2003, Westkapelle, the Netherlands. |
photo
7869: 2cy LBBG, August 15 2003, Westkapelle, the Netherlands. |
photo
7874: 2cy LBBG, August 15 2003, Westkapelle, the Netherlands. |
photo
7885: 2cy LBBG, August 15 2003, Westkapelle, the Netherlands. |
photo
7943: 2cy LBBG, August 15 2003, Westkapelle, the Netherlands. |
photo
7969: 2cy LBBG, August 15 2003, Westkapelle, the Netherlands. |
photo
7983: 2cy LBBG, August 15 2003, Westkapelle, the Netherlands. |
photo
7994: 2cy LBBG, August 15 2003, Westkapelle, the Netherlands. |
Photo
1: LBBG
2cy, August 24 2000, Le Portel, France. |
Photo
2: LBBG
2cy, August 24 2000, Le Portel, France. Note new rectrices. |
Photo
3: LBBG
2cy, August 24 2000, Le Portel, France. Typical bird. |
Photo
4: LBBG
2cy, August 24 2000, Le Portel, France. |
Photo
5: LBBG
2cy, August 23 2000, Le Portel, France. Showing moult score. Note the
secondaries. |
Photo
6: LBBG
2cy, August 23 2000, Le Portel, France. Another
typical graellsii.
|
Photo
7: LBBG
2cy, August 25 2000, Le Portel, France. |
Photo
8: LBBG
2cy, August 25 2000, Le Portel, France. |
Photo
9: LBBG
2cy, August 23 2000, Le Portel, France. Ringed
in Belgium. Advanced bill-colour. |
Photo
10: LBBG
2cy, August 24 2000, Le Portel, France. |
Photo
11: LBBG
2cy, August 24 2000, Le Portel, France. Ringed in Belgium. |
Photo
12: LBBG
2cy, August 24 2000, Le Portel, France. |
Photo
13: LBBG
2cy, August 25 2000. |
Photo
14: LBBG
2cy, August 25 2000, Le Portel, France. |