sub-adult
fuscus: July
updated: 05-08-2005 On this page, you'll find a summary of “Baltic Lesser Black-backed Gull Larus fuscus fuscus – moult, ageing and identification”, by Lars Jonsson, as published in Birding World Volume 11 number 8, 1998. We have added some extra images, most of ringed birds (so proved origin). The article by Jonsson concentrates on the field identification of fuscus. He presents new (1998) information for the identification and ageing of immature birds. As the article was published in the British magazine Birding World, Jonsson emphasizes on identification of out of range birds in the U.K. or continental NW Europe. He stresses that "basic understanding of the moult, plumage development and migration of the form fuscus are necessary for correct identification of such birds". This article is often referred to, and for a while, was standard reference and only literature for the Dutch Rarity Committee to reject or accept out of range fuscus for the Dutch list. Nowadays, with better understanding of the taxon intermedius, it seems wise to focus on ringed birds only. On this page, we try to bring together information of graellsii and intermedius, which is relevant in identification of fuscus. Most of the data were already published on various pages in the Lesser Black-backed Gull Section or could be found on the "discusfus" page. Moult,
ageing and identification of fuscus - Lars Jonsson Materials
and methods
Jonsson
studied fuscus on Gotland, SE Sweden, where it is a common breeder
in a few large colonies. He also visited museum collections at Tring,
Stockholm, Gothenburg, Copenhagen, Helsinki and New York. He observed graellsii
and intermedius in Sweden, Denmark, England, Spain and Morocco. The
ringing recoveries of Fenno-Scandinavian fuscus in Western Europe
are analysed briefly, mainly to see if they support evidence for the
European status of fuscus. To increase objective measurements on
museum specimen, Jonsson used a 20 steps Kodak grey scale to classify dead
skins. |
LBBG fuscus 11cy CA82, July 09-14 2003, Tampere, Finland. Ringed as pullus in Finland on July 05 1993. All primaries still old by mid July. | ||||||
LBBG fuscus 8cy C103, August 06 2002, Tampere, Finland. Ringed as pullus in Finland on July 01 1995. All primaries still old by early August. | |||||||
LBBG graellsii ALH, April 19 2003, Maasvlakte, the Netherlands. Typical LBBG from Britain. Primary moult finished last autumn. | |||||||
LBBG graellsii BTO FP-53605, April 05 2003, Maasvlakte, the Netherlands. An adult ringed in Britain, now breeding in SW Holland. | |||||||
LBBG graellsii 5cy AHAS, May 29 2003, Zeebrugge, Belgium. So-called Dutch intergrades. | |||||||
LBBG graellsii Bruxelles L 4483?, April 16 2001, Maasvlakte, the Netherlands. Typically "graellsii grey" individual. | |||||||
Systematic
position, nomenclature and behaviour
Most authors treat Larus fuscus as a single species, represented in Europe by three subspecies: graellsii, intermedius and fuscus (e.g. Barth 1975, Grant 1982, Cramp 1983). However, from the early 90’s authors stressed the differences between western and eastern birds (Strann & Vader 1992, Sibley & Monroe 1993). Based on genetic research by Sangster in 1998, the Dutch Rarity Committee decided to separate Baltic fuscus from the western forms graellsii and intermedius, which were lumped and regarded “the” Lesser Black-backed Gull. Indeed, there are a few obvious features in fuscus that isolate it from the other two taxa; nonetheless it is not easy to draw a definite line between fuscus and graellsii/intermedius. Geographic isolation of fuscus may have resulted in these differences, but still, the shared genetic heritage is obvious when observing the three forms. Jonsson doesn’t take strong position in the nomenclature debate, as he feels uncomfortable in the arrangements purposed; i.e. Greater Black-backed Gull, Lesser Black-backed Gull and Baltic Gull. Identification in the literatureEarlier
literature focused most on adult bird and mention differences in upper-part
coloration and structure. In his article, Jonsson enlarges upon the immature
plumages as well,
especially second and third calendar year birds. |
LBBG intermedius Stavanger 4107441, November 01 2002, Westkapelle, the Netherlands. Dark grey LBBG from Norway. Primary moult score, PMS of 44 (typical intermedius). | ||||||
LBBG intermedius Stavanger 4134634, Westkapelle, the Netherlands, November 02 2002. PMS of 38. | |||||||
LBBG 5cy+ intermedius JM79, October 19 2002, Westkapelle, the Netherlands. Ringed in Norway. PMS of 36 / 37. | |||||||
Distribution
in Europe
At
the turn of the century, Lesser Black-backed Gull showed a much-restricted
breeding range than today. Graellsii could be found in the U.K. and
the Faeroes, intermedius was bound to western Scandinavia and fuscus
was widespread in the Baltic Sea, northern Fenno-Scandinavia and northwest
Russia. Graellsii expanded northwards to Iceland in the 1920’s
and westwards to the Netherlands in the 1930’s. A dramatic increase
followed, with influences of both graellsii and Scandinavian intermedius
in the Dutch colonies. These Lesser Black-backed Gulls are often referred
to as “Dutch intergrades”. Similar birds nowadays breed along the
French Atlantic coast and in the Spanish Ebro Delta. In the 1990’s, intermedius
has increased its breeding area into former fuscus area: the Danish
islands and the Lofoten area of northern Norway. (see Distribution
Section). Barth
(1968) describes the division lines between intermedius and fuscus
in Scandinavia. The two meet along the coast of central Norway near Tarva
and in the waters of Kattegat, eastern Denmark. Birds from the island
Anholt are intermedius and those from the island Saltholm (Oresund)
seem to be belong to the taxon fuscus. According
Jonsson, the wintering quarters of intermedius can be found in the
western Mediterranean (Italy and westwards), and only a fraction can be
found in western Africa, south of the Sahara. Recent ringing programmes in
southern Norway and the Netherlands indicate than many birds do migrate
far south and can be found in Morocco, and further south along the rich
fish coasts to Mauritania. There is at least one ring reading from inland
Congo, an intermedius ringed in Norway. In migration distance, this
bird resembles fuscus, which can be found in great lakes of the
Rift Valley in eastern Africa or even S Africa. But fuscus spend the winter also
further north: the Persian Gulf and eastern Mediterranean (Egypt, Israel). How
to find fuscus in western Europe Jonsson
studied local gulls in south Sweden, checking intermedius and graellsii
among local fuscus and this is the basis for his paper. With the
increase of western taxa, he finds 10% of resting gulls to belong to graellsii/intermedius
in the late 1990’s. His advice for search fuscus in western
Europe: gain good working knowledge of the variability within intermedius
and graellsii by constant study of local gulls. To find out of
range fuscus, one should take into account the main arrival and
departure periods for fuscus. And understand the
complicated moult pattern exhibited by fuscus. However, individual
birds may be difficult to interpret accurately, and it’s probably best
to focus on obvious individuals, with borderline fuscus candidates
left unidentified until more information is at hand. Jonsson
targets three best options:
Jonsson
stresses the difficulty of labeling small, slim and black-mantled birds
arriving back from Africa in spring as fuscus. There is no 100%
certainty in these birds, as all features may apply to intermedius
as well. Added to this, adult fuscus from the southern Baltic has a
mantle colour which overlaps to a high degree with intermedius.
(See Barth's map). |
LBBG intermedius Stavanger 4210403, Westkapelle, the Netherlands, November 05 1999. Photo by Pim Wolf. A small, dark grey LBBG, reminiscent of fuscus. PMS of 42. | ||||||
LBBG intermedius 13cy Copenhavn 4124822, Breskens, the Netherlands, October 25-27 1999. Ringed in Jylland. Upper-parts dark grey, but PMS of 41. | |||||||
LBBG intermedius 12cy Stockholm 8071437, 26 November 2000, Westkapelle, the Netherlands. Upper-parts mid-grey and PMS of 45. | |||||||
LBBG intermedius 9cy Stockholm 8082746, December 21 2000 Westkapelle, the Netherlands. Slaty-grey intermedius from Malmö. Primary moult just finished. | |||||||
LBBG fuscus 6cy C69E, August 06 2002, Tampere, Finland. Ringed as pullus, Finland on July 03 1997. Rather paler grey adult. | |||||||
LBBG fuscus 8cy C95C, July 12 2003, Tampere, Finland. Ringed as pullus in Finland on July 16 1996. Rather pale grey adult. | |||||||
LBBG fuscus CE10, August 12 2002, Tampere, Finland. Ringed as pullus at Korpilahti, Finland on July 03 1993, now in 10cy. Primaries P1-P2 are new, P3-P10 are still old. | |||||||
LBBG fuscus 3cy C9NN, July 09-12 2003, Tampere, Finland. Ringed as pullus at Kanala, Finland on June 24 2001, now in 3cy. Primaries, secondaries and rectrices all 3rd generation. | |||||||
LBBG fuscus 3cy C3RH, August 08 & 12 2002, Tampere, Finland. Ringed in Finland, white C3RH. Arrested moult at P8. | |||||||
LBBG fuscus 6cy HT 203.880, July 10 2003, Tampere, Finland. Ringed as pullus in Finland on July 03 1998. Adult with pale covert fringes. | |||||||
Ringing
recoveries in western Europe and Africa
Fuscus
is a long-distance migrant and follows a south or southeasterly route to
the winter grounds. Prior to migration, fuscus and intermedius
forage both together in eastern Denmark, and from here some fuscus
may take a wrong route, bringing them into the North Sea area. Ringing
programs were started in eastern Scania and Blekinge (south-eastern
Sweden), and from these sites 71 recoveries were made outside Sweden. Only
two recoveries were made north or west of Denmark, 29 were from within
Denmark (Bornholm excluded). Sweden
and Finland have ringing programs on larger scale with 15 recoveries in
western Europe prior to 1998. Nine birds were juvenile / first winter
birds and 5 birds were in 2nd calendar year or early 3rd
calendar year. Only one adult has been discovered. A word of caution is
necessary where juveniles are involved, as numbers can be influenced by
misidentification of argentatus Herring Gulls when pulli were
ringed. Nevertheless, there is evidence that some fuscus may follow
a more westerly route, as two Finnish ringed birds have been
rediscovered in Portugal and in Valencia, definitely outside the range of argentatus.
Another 7 records come from north-western Africa (Spanish Sahara –
Algeria), most probable fuscus as well. Interestingly, this is the
main wintering area for intermedius, and it’s easy to construct a
picture of these fuscus moving north again with intermedius
flocks in spring, finding their way into the North Sea area. The
main wintering grounds for fuscus must be located in tropical
Africa. According Jonsson, the eastern Mediterranean host only small fuscus
numbers, although the majority of ring recoveries from recent Finnish
project come from Israel, probably due the more densely ornithologist
network in Israel (Hannu Hoskinnen, pers comm.). It
is normal for fuscus to winter on the Benin coast, as far west as
Ghana, based on Swedish ring recoveries. Swedish fuscus can be
found evenly distributed from Ethiopia to Ghana and here, in Ghana, intermedius
is common as well. Jonsson believes that Swedish fuscus must follow
a route straight south through central Europe (with records in Italy,
Tunisia and Libya) and subsequent passage over the Sahara dessert in a
straight line, supported by early reports of juveniles in sub-Sahara
Africa (e.g. Chad, September 20th). This idea is further
supported by evenly distributed Swedish ringed fuscus in Africa: 19
records in western Africa and 14 records in eastern Africa (24°E
longitude). If one presumes a solely eastern route, a bias in eastern
African records would be expected as well, Jonsson states. The ring records from Swedish and Finnish fuscus in Britain are most suspicious according Jonsson, and the same can be said about records from the Netherlands, which were treated by Hogendoorn & Scheepen in 1998. Identification of
adult fuscus
|
Foreign
ring recoveries of Finnish (by 22 Oct 1999, n = 940). |
||||||
Chart of Munsell value for graellsii Although figures have been prepared with most care, I take full responsibility for all errors in any chart and table. | |||||||
Chart of Munsell value for intermedius | |||||||
Chart of Munsell value of fuscus | |||||||
Table of results from Barth's research | |||||||
Map with clustered column charts for Scandinavian location. Aggregate stacked charts. | |||||||
Based
on field experience, intermedius is generally larger and slightly
more heavily built than fuscus. The difference between fuscus
and British graellsii is very obvious, with fuscus looking
long-winged and darker. Graellsii is more powerful with full breast
and short rear end, not as attenuated as in fuscus. However, one
must keep in mind the differences between small females and larger
males. The
late Edward Barth, a Norwegian ornithologist working for the museum of
Oslo, has written the most authoritative work on grey-tones of intermedius
and fuscus (Barth 1966, 1968, 1975). The results are summarized on this
page. Jonsson concludes: “the mere fact that a Lesser Black-backed Gull looks darker than a typical intermedius, and may even appear black-looking, is not enough for a sub-specific identification”. Jonsson's material shows an approximate 15% overlap between fuscus from the east Swedish coast and intermedius from west Sweden. This means that every seventh or eighth intermedius will look like a pale fuscus, and visa versa.
Barth’s
research also enlarged upon the brown hue (chroma) in old feathers, a
feature commonly encountered in fuscus. Intermedius retains
a neutral lead-grey tone, even when the feathers are old. Bleached intermedius
scapulars and wing-coverts should be described as cold brown or
milky brown, where fuscus show a deep fruity warm brown mahogany
hue on old feathers. |
20 | 000000 | RBG 000 | ||||
19 | 0D0D0D | RBG 013 | |||||
18 | 1B1B1B | RBG 027 | |||||
17 | 282828 | RBG 040 | |||||
16 | 363636 | RBG 054 | |||||
15 | 434343 | RBG 067 | |||||
14 | 515151 | RBG 081 | |||||
13 | 5E5E5E | RBG 094 | |||||
12 | 6B6B6B | RBG 107 | |||||
11 | 797979 | RBG 121 | |||||
10 | 868686 | RBG 134 | |||||
09 | 949494 | RBG 148 | |||||
08 | A1A1A1 | RBG 161 | |||||
07 | AEAEAE | RBG 175 | |||||
06 | BCBCBC | RBG 188 | |||||
05 | C9C9C9 | RBG 201 | |||||
04 | D7D7D7 | RBG 215 | |||||
03 | E4E4E4 | RBG 228 | |||||
02 | F2F2F2 | RBG 241 | |||||
01 | FFFFFF | RBG 255 | |||||
Basic moult in
adult fuscus
Several
authors mention the late start of the primary moult in adult fuscus,
only after arrival at the wintering grounds. However, adult fuscus
regularly start moulting the innermost primaries on the breeding grounds
(although late). Hario (1982) already established this phenomenon (see summary
on this page). Jonsson surveyed resting birds, and he estimates
60% of adult-like fuscus from July to mid-September to have started
shedding the inner primaries P1 or P1-P2 by the end of August. Only very
rarely adult-like birds have dropped P3 as well. This
is different from what generally can be found in intermedius and graellsii.
Intermedius in late-August or early-September are normally more
advanced in primary moult, with P4-P6 growing at this time (See here).
Peter Stewart, doing research on graellsii in the U.K., found only
one out of 98 birds from September 01, which dropped just P1 and P2.
Jonsson stresses the apparent difference: intermedius with advanced
moult in the primaries and normally cold grey scapulars or feathers with a
‘milky brown’ hue on the old feathers. In the mean time, when birds
are growing P4, they normally show active moult in the wing-coverts as
well, replacing the median, lower lesser coverts and the outer greater
coverts. This strongly contrast with fuscus, which show delayed
moult: at most the two inner primaries dropped and strong warm brown
mahogany hue on the old feathers. Active moult in the wing-coverts is
suspended until arrival at the wintering grounds. In the Netherlands, we regular check 1.000's of Lesser Black-backed Gulls by late August and early September (see here and here). On all occasions, several birds showed delayed moult in the primaries and this is what Jonsson mention as the ‘potential pitfall’. However, says Jonsson, still a 40% of Swedish fuscus depart to Africa and the Mediterranean without a single sign of primary moult. This is very rare in intermedius (although still possible). Jonsson
summarizes the correct combination of features in adult autumn fuscus:
Also,
the out of range bird has to be structurally distinct from its neighbours,
to be identified as vagrant fuscus in late August or early
September. A word of caution: remember that some graellsii and intermedius
may arrest the primary moult, so show a full primary set in autumn (see here
and here). Fuscus start / continues the primary moult on the wintering grounds, and finish this primary moult in February – March, just prior to northward migration. Some birds may migrate with growing outer primaries, some other adults include the innermost primaries again in the moult in spring. Hence, they show fresh primaries in spring, but remember that its not uncommon to find intermedius and graellsii with recently replaced inner primaries in spring as well. Therefore it seems wise to focus on adult birds in autumn. |
LBBG fuscus 5cy C2ER, July 09-17 2003, Tampere, Finland. Ringed in Finland on July 03 1999. All primaries still old. | ||||||
LBBG fuscus 5cy C7EU, July 09-10 2003, Tampere, Finland. Ringed as pullus in Finland on July 04 1999. All primaries still old. | |||||||
LBBG fuscus 5cy CKP0, July 09 2003, Tampere, Finland. Ringed as pullus in Finland on July 01 1999. P1 missing, P2-P10 old. | |||||||
LBBG fuscus 6cy CAA1, July 09-11 2003, Tampere, Finland. Ringed as pullus in Finland on July 11 1998. P1 new, P2 growing, P3-P10 old. | |||||||
LBBG fuscus 6cy CAW1, July 12-15 2003, Tampere, Finland. Ringed as pullus in Finland on June 30 1998. P1-P5 fresh, P6-P10 older. | |||||||
LBBG fuscus 6cy C3H4, July 10-17 2003, Tampere, Finland. Ringed as pullus in Finland on July 09 1998. P9-P10 old, P10 with a large mirror. Strong mahogany hue (chroma). | |||||||
LBBG fuscus 7cy C7R7, July 09-15 2003, Tampere, Finland. Ringed as pullus in Finland on June 30 1997. All primaries still old. | |||||||
It
is difficult to describe a “typical”
juvenile fuscus, as they are as variable in this plumage as
other large white-headed gulls. In general they show more contrast than
juvenile intermedius and graellsii, according to Jonsson.
However, many birds are not conspicuous in this respect. Jonsson focuses
on “the personality” of fuscus, rather than on diagnostic
features, as there is probably not a single definite characteristic. The post-juvenile moult
in the scapulars and sides of the breast may start as early as late
August. Fuscus migrate quickly; mirrored by early arrival dates in
Africa: e.g. Uganda September 24, Angola September 29, and Zaire October 04.
Juvenile fuscus arrive in (almost) complete juvenile plumage
(advanced birds have the scapulars moulted), but they probably start
moulting rapidly. The new scapulars are dark slaty-grey with a blackish
wedge-shaped shaft-streak. Some show an anchor pattern on the new
second-generation scapulars, according Jonsson. Both patterns can be found
in intermedius as well. |
LBBG fuscus 1cy CCVJ, August 06-12 2002, Tampere, Finland. Medium dark brown centres of scapulars and dark outer greater coverts. The fringes are rather pale, almost white lacking a buff or yellowish hue. | ||||||
LBBG fuscus 1cy CHR6, August 06 2002, Tampere, Finland. Fringes of the scapulars slightly worn. Very dark brown centres of scapulars and very dark outer greater coverts. Most striking is the small size & slender bill, but it's hard to draw a clear line for identification. | |||||||
LBBG intermedius 1cy J07J, September 22 2002, Boulogne/Mer, NW France. Ringed in Norway. | LBBG 1cy Stavanger, August 28 2003, IJmuiden, the Netherlands. Ringed in Norway. | LBBG intermedius 1cy Stavanger 4238324, September 22 2002, Boulogne/Mer, NW France. A bird ringed in Norway last summer. | LBBG fuscus 1cy CCUR, August 06-12 2002, Tampere, Finland. This bird and the individual from the same nest, CCVJ, were still begging at the parent at the dump. | ||||
Second calendar year: fuscus in spring On the wintering grounds, the wing-coverts are moulted when most of the scapulars have been replaced; probably in the same sequence as in the complete moult (basic moult), and the coverts are all or almost all replaced by late January or February. Considering the wear of these wing-coverts in spring in Scandinavia, they must have been moulted within a very short period, as in many birds the abrasion and bleaching of the feathers is almost equal in the complete panel. Only after finishing the moult in the wing-coverts, 2cy fuscus start to moult the fight feathers in February according to Jonsson. He described ten 2cy fuscus from late January in Israel and none had shed any primary, but he doesn't enlarge upon the covert moult stage. In
museum collections, Jonsson found four birds: one 2cy fuscus from late
January, growing P1 and P2. Two other birds from April, found in Angola
also showed moult in the primaries (moult scores 13 and 46) and another
bird from Aden almost finished its primary moult in early May (moult score
39). For explanation of moult scores: see Topography
Section. Primary
moult starting in February just fits in the fuscus picture, as this
replacement takes over 4 months in large white-headed gulls. Thus, 2cy
birds are just in time to finish this moult to migrate north again by
late-May – June. From 1995 to 1998 Jonsson described 2cy fuscus after arrival at Gotland, south Sweden, and these birds showed a wide range of variation. Most 2cy birds finished moulting all of the flight feathers by late April and May, others arrested moult in the primaries prior to migration. However, a small part of 2cy fuscus return in Scandinavia with all flight feathers still juvenile. The
exact extend of secondary moult is not mentioned by Jonsson (as this is
hard to obtain from field research), but he presumes that most 2cy birds
have the secondaries largely replaced for second-generation feathers. Most
birds (Jonsson mentions “second summer”, but this should be
“first” summer probably) have moulted the rectrices as well. Contrary
most literature, Jonsson presumes that 2cy fuscus do regularly migrate
north, but the position of the wintering grounds (either Mediterranean or
Africa) of these returning birds is unknown. Jonsson estimates that “a
substantial proportion of the total number of this age-class” is
involved. The vanguard of second calendar year birds normally returns July
01, after a one-month journey north. |
LBBG fuscus 2cy C3VS, July 16-17 2003, Tampere, Finland. Typical Finnish 2cy fuscus with 2nd generation primaries, secondaries and tail. | ||||||
LBBG fuscus 2cy CJUC, July 14-17 2003, Tampere, Finland. Advanced 2cy fuscus in Finland, moulting the inner primaries to 3rd generation. Tail and secondaries are 2nd generation. | |||||||
LBBG fuscus 2cy MC24, July 09-17 2003, Tampere, Finland. 2cy fuscus from E Sweden, reminiscent of Finnish fuscus in moult, but slightly more powerful in jizz. | |||||||
LBBG fuscus 2cy C5UJ, August 08 2002, Tampere, Finland. The average 2cy fuscus in Finland. P1-P9 moulted and the picture shows the abraded tip of P10. | |||||||
LBBG fuscus CNMR, August 2002 (2cy) & July 2003 (3cy), Tampere, Finland. P10 still juvenile in 2cy, moulting inner primaries in August. P10 2nd gen in 3cy, again moulting inner primaries. As 2cy arrested moult in the secondaries. | |||||||
Second
calendar year fuscus in autumn – third calendar year fuscus
in spring The
second renewal of the primaries may start during the summer months in
Scandinavia, but most will moult the primaries after migration to Africa
again. Jonsson examined eight birds from museum collections and there is a
lot of irregularity involved in moult sequences of autumn 2cy birds. In
his opinion, 2cy birds in autumn are not moulting the primaries in the
ordinary sequence (from P1 to P10), but in “waves”. Jonsson doesn’t
enlarge upon these waves, but the final result, when 3cy birds arrive in
spring, will be obvious visual moult steps in the primaries (normally at
P6, P7, P8 or P9). This pattern of arrested moult is regularly found in
3cy fuscus and must be a common characteristic. Jonsson examined two 2cy birds found in Africa in October; both were actively moulting the outer primaries. This is a nice example of “continuation after suspension”. Moult of the primaries continues after suspension in the outer primaries (moulted to second-generation) and subsequently birds start at P1 again (moulted to third-generation). Prior to spring migration, 3cy fuscus arrest primary moult again in the outer primaries, resulting in the obvious moult step when they return in Sweden by late-April and early-May. The obvious mirror on P10 can be explained by the late requirement of this second-generation P10, which is therefore more adult-like in appearance. Identification of 2cy fuscus from intermedius/graellsii If
one attempts to find fuscus in NW Europe, the most obvious option
is to look for 2cy birds with a new set of flight feathers in July or
August. Ordinary graellsii and intermedius start the primary
moult by the end of April or from May onwards. Hence, 2cy birds with new
primaries in July should be fuscus, if other (structural) features
support this identification. |
LBBG fuscus 2cy C6XV, August 07 2002, Tampere, Finland. Advanced 2cy fuscus: all primaries 2nd generation. Median and inner greater coverts replaced for 3rd generation. | ||||||
LBBG fuscus 3cy C5XE, July 10-16 2003, Tampere, Finland. Ringed in Finland on June 28 2001. P1-P3 new, P4 missing, P5-P10 old. | |||||||
LBBG fuscus 3cy C5XM, July 10-16 2003, Tampere, Finland. Ringed in Finland, now in 3cy. Left wing: P1-P2 old 2nd generation, P3-P5 3rd gen, P6-P8 old 2nd gen, P9-P10 fresh 2nd gen. | |||||||
In
2cy July fuscus, the head feathers are moulted and look scruffy
(moth-eaten). Some birds seem to renew all the body-feathers and look
fresh in summer. The bill is largely dark with pale base but may show red
at the gonys. The upper-parts consist of old sepia brown worn
second-generation feathers, mixed with almost black fresh third-generation
feathers. Many birds renew the wing-coverts on the wintering grounds, and
these coverts look worn when they return in Scandinavia. The
second-generation coverts show little pattern, although notches may be
visible on the greater coverts. Jonsson
stresses the difference between these coverts in fuscus and intermedius,
but this is a too simplified picture. Wing-covert moult, tail-feather
moult and secondary moult in intermedius is not necessarily
initiated in summer. Many birds start this moult much earlier, already on
the wintering grounds and are very reminiscent of fuscus in this
respect. Moreover, intermedius may start the scapular moult to
third generation as early as June. However, it has still to be proven that
2cy intermedius may return with second-generation flight feathers
in spring, as many fuscus do. Such birds can be found in NW Europe,
but none was ringed so far. On
Gotland, Jonsson found several 2cy fuscus which failed to moult the
flight feathers on the wintering grounds, thus in line with other European
gull species. He describes two of such birds in his article, to emphasize
the differences with graellsii/intermedius. One bird, he admits,
would be difficult to identify as fuscus outside the normal range,
but the other one shows diagnostic features, i.e.:
Research
on 2cy intermedius and graellsii in the Netherlands reveal
these features can be found in intermedius as well. Second
generation wing-coverts and tail are not uncommon in June. Furthermore, it
seems there is no species of large white-headed gull with a primary moult
score range as large as in Lesser Black-backed Gull and intermedius with
primary moult score of 2 -exceptionally low- can be found by mid-July.
(See 2cy LBBG July Section) Identification
of 3cy fuscus from intermedius/graellsii 3cy
fuscus is probably the most rewarding plumage to look for in NW
Europe. Jonsson accentuates the colour of upper-parts and stage of moult
in the wing-coverts. The fresh feathers are much darker, blackish, and 3cy
fuscus is much advanced in wing-coverts moult compared to graellsii/intermedius.
This is not correct. Many 3cy intermedius show a complete
adult-like wing-covert panel, and as Jonsson stated earlier, the
upper-part grey-tone of intermedius may overlap with fuscus.
Jonsson states: “I would positively identify a second-summer Lesser Black-backed Gull in May showing predominantly dark wing-coverts and very fresh inner six to eight primaries as fuscus”. Jonsson examined 9 intermedius from museum collections, which were all much graellsii-like. This sample doesn’t reflect the variation found in the field by us. Arrested moult in the primaries is not uncommon in intermedius, and it is found in graellsii too. Several ringed intermedius and Dutch intergrades have been observed, showing arrested moult at P6, P7, P8 or P9. Interestingly, this advanced moult in the primaries correlates with advanced moult in the wing-coverts, resulting in a more adult-like appearance. Although arrested moult in 3cy intermedius is not common in May (about 5%), it starts to be more common in June (estimated 10% in 2003). Although Jonsson describes the tail of 3cy intermedius usually to be of one single generation, this is simply not true: plain white tail-feathers are commonly growing in 2cy October-November birds or in 3cy March-April birds. When returning in the Netherlands, 3cy intermedius may show a plain white tail in June. Identification
of sub-adult fuscus Sub-adult fuscus look very adult-like, although a few bleached brown wing-coverts or black spots in the tail may still be present. Jonsson hesitates to name features to isolate a consistent third-summer type plumage. References (selection)Baker,
R.R. 1980. The significance of the Lesser Black-backed Gull to
models of bird migration. Bird Study 27:41-50. Barth
E.K. 1966. Mantle colour as a taxonomic feature in Larus argentatus
and Larus fuscus. Nytt Mag. Zool. 13, 56-82. Barth
E.K. 1968. The
circumpolar systematics of Larus argentatus and Larus fuscus
with special references to the Norwegian population. Nytt
Mag. Zool.
15, suppl: 1-50. Barth
E.K. 1975.Taxonomy of Larus argentatus and Larus fuscus in
north-western Europe. Ornis. Scand. 649-63. Bergman,
G. 1982. Population dynamics, colony formation and competition in Larus
argentatus, L. fuscus and L. marinus in the archipelago of Finland. Ann.
Mag. Zool. 19:143-164. Cramp
S. & Simmons K.E.L. (ed) 1983. The Birds
of the Western Palearctic, Vol 3. Oxford University Press. Filchagov
A.V., Bianki V.,Cherenkov A.E. & Semanshko V.Yu. 1992. Interaction
between Lesser Black-backed Gull Larus fuscus and West-Siberian
Gull L. heuglini in the contact zone. Zool. Zh. 71:148-152 (in
Russian). Grant
P.J. 1986. Gulls, a guide to identification (2nd ed) Calton. Hario
M, 1984. Onset and pattern of primary moult in the Lesser Black-backed
Gull Larus f. fuscus – a comparison with the Herring Gull L.
argentatus. Ornis Fennica 6:19-23. Hario,
M. 1994. Reproductive performance of the nominate Lesser Black-backed Gull
under the pressure of Herring Gull predation. Ornis Fennica 71:1-10. Hario, M. Bianki, V. & Zimin, V. 1998. Larus fuscus fuscus. IN: Kotiranta, H. Uotila, P., Sulkava, S. & Peltonen, S-L. (ed). Red data book of eastern Fennoscandia. Helsinki (pp 247-249). Humphrey,
P.S. & Parkes, K.C. 1963. Comments on the study of plumage succession.
Auk 80:496-503. Johnson,
C. 1985. Biochemical variation in populations of Larus argentatus and
Larus fuscus in northwest Europe. Biol Journ. Linn. Soc. 24:349-363. Kilpi,
M. & Saurola, P.1983. Geographic distribution of breeding season
recoveries of adult and immature Larus marinus, L. argentatus and L.
fuscus ringed in Finland. Ornis Fennica 60:117-125. Payne, R.B. 1972. Mechanisms in control of molt. IN: Farner, D.S. & King, J.R. (ed). Avian Biol Vol 2:103-155. Acad Press New York. Rock,
P. 1999. The efficacy of the colour-ringing system used for Herring Gull
Larus argentatus and Lesser Black-backed Gull Larus fuscus in Bristol
1980-1997. Ringing & Migration 19:306-310. Sibley
C.G. & Monroe B.L. 1993. A supplement to the distribution and taxonomy
of the birds of the world; 39. New Haven & London. Strann K-B. & Vader W. 1992. The nominate Lesser Black-Backed Gull Larus fuscus fuscus, a gull with a tern-like feeding biology, and its recent decrease in Northern Norway. Ardea 80: 133-142. Stresemann E. & Stresemann V. 1966. Die Mauser der Vögel. Journ f Ornith. (sonderheft) 224-232.Verbeek,
N.A.M. 1977. Timing
of primary moult in adult Herring Gull and Lesser Black-backed Gulls.
Journ Ornith. 118:87-92. |
LBBG fuscus 3cy C8CM, July 09-11 2003, Tampere, Finland. Ringed as pullus at Ruoves, Finland on July 04 2001, now in 3cy. Primary moult arrested on P7. | ||||||
LBBG fuscus 3cy C8XC, July 10-11 2003, Tampere, Finland. Ringed as pullus at Kanala, Finland on June 28 2001, now in 3cy. Active moult in the inner primaries. | |||||||
LBBG fuscus 3cy C2A5, July 10-17 2003, Tampere, Finland. Ringed as pullus at Palkan, Finland on June 25 2001, now in 3cy. Primary moult arrested at P7. | |||||||
LBBG fuscus 3cy C0NM, July 10-17 2003, Tampere, Finland. Ringed in Finland, now in 3cy. Active moult in the inner primaries: P1 new, P2-P3 missing. | |||||||
LBBG fuscus 3cy C4XR, July 09-17 2003, Tampere, Finland. Ringed in Finland, now in 3cy. Primary moult arrested on P6. | |||||||
LBBG fuscus 4cy C0PA, July 11-17 2003, Tampere, Finland. Ringed at Luopio, Finland on July 04 2000. | |||||||
LBBG fuscus 4cy C1CK, July 10-15 2003, Tampere, Finland. Ringed at Vilppu, Finland on June 30 2000. | |||||||
LBBG fuscus 4cy C1MS, July 10-17 2003, Tampere, Finland. Ringed at Luopio, Finland on July 04 2000. | |||||||
LBBG fuscus 4cy C1NU, July 16-17 2003, Tampere, Finland. Ringed at Luopio, Finland on July 04 2000. | |||||||
LBBG fuscus 6cy C2H9, August 2002 & July 2003, Tampere, Finland (61.33N 24.59E). Ringed as pullus at Palkan, Finland on July 09 1998, Sub-adult in 2002. | |||||||
LBBG fuscus 4cy C3RH, July 07 2003, Tampere, Finland. Ringed in 2000. | |||||||
LBBG fuscus 4cy C5AR, July 10-17 2003, Tampere, Finland. Ringed at Sahala, Finland on July 04 2000. | |||||||
LBBG fuscus 4cy C6MR, July 11-16 2003, Tampere, Finland. Ringed at Luopio in 2000. | |||||||
LBBG fuscus 4cy C6RA, July 09-15 2003, Tampere, Finland. Ringed at Luopio, Finland on July 02 2000. Sub-adult fuscus by mid-July are very adult-like. P1-P10 still old. | |||||||
LBBG fuscus 4cy C7PA, July 09-17 2003, Tampere, Finland. Ringed in Luopio in 2000. | |||||||
LBBG fuscus 8cy CX18, July 10-16 2003, Tampere, Finland. Ringed as pullus in Finland on June 30 1996. All primaries still present. | |||||||