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LBBG rings
lbbg 1cy May
lbbg 1cy June
lbbg 1cy July
lbbg 1cy August
lbbg 1cy September
lbbg 1cy October
lbbg 1cy Nov - Dec
lbbg 2cy Jan-Febr
lbbg 2cy Mar-April
lbbg 2cy May
lbbg 2cy June
lbbg 2cy July
lbbg 2cy August
lbbg 2cy September
lbbg 2cy October
lbbg 2cy Nov - Dec
lbbg 3cy Jan-April
lbbg 3cy May
lbbg 3cy June
lbbg 3cy July
lbbg 3cy August
lbbg 3cy September
lbbg 3cy October
lbbg 3cy Nov - Dec
lbbg sub-ad Jan-April
lbbg sub-ad May
lbbg sub-ad June
lbbg sub-ad July
lbbg sub-ad Aug
lbbg sub-ad Sept
lbbg sub-ad Oct
lbbg sub-ad Nov - Dec
lbbg ad January
lbbg adult February
lbbg adult Mar-April
lbbg adult May
lbbg adult June
lbbg adult July
lbbg ad August
lbbg ad September
lbbg ad October
lbbg ad Nov - Dec
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sub-adult/near-adult:
May
General desription
Normally,
5cy in May are extremely hard to separate from adults and the overlap in characteristics
is severe. Probably, the only certain clue can be found in ringed birds.
Furthermore, 4cy & 5cy LBBG's can be found in colonies, in full May
courtship and raising chicks in August;
clearly they participate in the the ordinary mating cyclus as adults do. By
May, 4cy birds from graellsii populations can be distinguished from
adults quite easily (see e.g. image 1 and
image 2 and the ringed birds E056E
here and E104E
here) by e.g.:
- extensive black on the bill, but black
may be lacking
- pale
blue-yellow or white-yellow iris, but may be clear yellow as well
- pale yellow legs in some birds
- extensive streaking on the head in
some birds
- many brown-grey coverts, often in the
central greater coverts
- relatively small mirror on P10, often lacking a mirror on
P9
- relatively small white tips on the
primaries
- vermiculate
feathers along the trailing edge.
We stress
that these features seem to apply on a more extensive scale in graellsii
than they do occur in intermedius, which in 4cy may be surprising
reminiscent of adults.
Arrested moult in
spring in sub-adult LBBG
In spring, it's not uncommon to find LBBG
with arrested moult in the primaries in the Netherlands. We do not believe
these birds to origin from nominate fuscus colonies, but rather are
representatives of both graellsii and intermedius. It is
known that nominate fuscus show arrested moult on a very regular
basis in spring (see the fuscus
sections), but the birds we encounter in NW Europe show all
features commonly found in either graellsii or intermedius.
We therefore believe that arrested moult is an uncommon but regular
phenomenon in the taxa graellsii and intermedius.
Images of LBBG showing arrested moult in spring (!) can be found on these
pages:
In most of these birds, the inner
primaries look very fresh, without extensive wear in the tips and
regarding wear, the outer primaries do not substantially differ what can
be found in other birds of similar age-classes. It therefore is believed
that most birds follow the common pattern of replacement in the complete
moult: i.e. all primaries are moulted between May - November. The inner
primaries then are replaced once again on the wintering grounds, somewhere
between January and April.
The intermedius
bird at the bottom of this page is illustrative for this: it is
still growing P8, so moult has not been finished yet at the time it
already migrated north again. The black-ringed T7PF
proofs arrested moult also occurs in British LBBG.
LBBG colonization
of Belgium
The Belgian magazine Oriolus
published a special edition on gulls, which we here summary, supplied with
extra data from the Netherlands. The very informative articles of Oriolus
give excellent insight in the development of gull colonies, illustrated
with many pictures, tables and charts and is highly recommended read stuff
for all interested in gulls.
"The Herring Gull Larus argentatus and Lesser Black-backed
Gull Larus fuscus as breeding birds in Flanders, Belgium",
by Eric Stienen, Jeroen van Waeyenberge & Harry Vercruijsse, published
in Natuur.Oriolus 68(3), July-September 2002, p 104-110.
Introduction
LBbG (L.
fuscus) only started breeding in Belgium in the mid 80's, with
dramatically increasing numbers in two decades, from one pair in 1985
to 2863 pairs in 2001. Colonization started at the coastal nature
reserve "Het Zwin" at Knokke, but numbers never exceeded
40 pairs here. Rapid development LBbG numbers came from the
reclaimed industrial harbour area of Zeebrugge from 1987 onwards
with 2695 pairs in 2001. Other colonies can be found at the inner
harbour of Zeebrugge and roof top breeders at Oostende, south
along the Belgian coastline (only 8 pairs in 2001).
Counting
method
Prior to hatching all nests in
the harbour of Zeebrugge were counted annually. From a high
watching point, the proportion numbers of nesting LBbG's compared
to Herring Gulls were estimated. Next step was counting all nests,
without discern of species, marking them with a small match stick
and discount the proportional ratio afterwards. For lacking annual
values, numbers of adjacent years have been used to estimate the
annual number, considering the long-term trends and development of
locations within the colony concerned.
Table
1 from: The Herring Gull Larus argentatus and
Lesser Black-backed Gull Larus fuscus as breeding
birds in Flanders, Belgium", E Stienen et all.
Number of breeding pairs of LBbG in each colony and total
numbers in Flanders during the period 1985-2001. * are
inter- and extrapolated numbers usd for missing
values. |
year |
Zwin |
Outer
harbour Zeebrugge |
Inner
harbour Zeebrugge |
Oostende |
total |
1985 |
3 |
- |
- |
- |
3 |
1986 |
2 |
- |
- |
- |
2 |
1987 |
3 |
- |
- |
- |
3 |
1988 |
1 |
- |
- |
- |
1 |
1989 |
1* |
- |
- |
- |
1 |
1990 |
2 |
0 |
- |
- |
2 |
1991 |
7 |
2 |
0 |
- |
9 |
1992 |
6 |
1 |
1 |
- |
8 |
1993 |
8 |
3 |
1 |
- |
12 |
1994 |
15 |
14 |
8 |
- |
37 |
1995 |
28 |
40 |
11 |
- |
79 |
1996 |
15 |
108 |
47 |
- |
170 |
1997 |
32 |
218 |
51 |
- |
301 |
1998 |
38 |
258 |
30 |
- |
326 |
1999 |
40 |
552 |
6 |
4 |
602 |
2000 |
35 |
1180 |
50 |
3 |
1268 |
2001 |
35* |
2695 |
125 |
8 |
2863 |
2002 |
- |
- |
- |
- |
- |
Results
LBbG only recently settled as
breeding species in Belgium and all colonies were occupied after Herring
Gulls settled for several years earlier. However, number of
Herring Gulls have been low over the first years, sometimes zero
over longer periods in the 1960's, and it's only from the mid
1990's, with the expansion of the industrial area of Zeebrugge
(especially the Outer harbour of Zeebrugge) that counts exceeded
100's. Outer harbour of Zeebrugge is the only place where numbers
of LBbG exceed Herring Gull numbers, now holding over 94% of the
Belgian population. The explosive expansion at the Zeebrugge
harbour was followed by expansion further south, at Oostende LBbG
started breeding on roof tops, as Herring Gulls already had been
doing from 1993 onwards, but numbers remain low. During the period
of 1992-2001, LBbG numbers almost doubled with an average increase
of 99,3%. An estimated 1,8% of all European LBbG's can be found in
Belgium.
Discussion
The rapid expansion in Belgian
colonies must be set in an international perspective. LBbG have
expanded dramatically over the last decades in NW Europe, now
breeding as far south as the Ebro Delta in Spain. In the
Netherlands, numbers of breeding LBbG have been growing strongly
over the years 1960-2000, now breeding in vast colonies along the
coast and inland industrial complexes and on roof tops.
There have been two "grow waves": by protection rules
early in the century and another by the increase in food supply
from the 1960's (fishery, agriculture and landfills). Now many
landfills in the Dutch Delta close, there is a strong decrease in
numbers of breeding Herring Gulls at e.g. Saefinghe (Westerschelde),
with numbers dropping from over 8.000 to just 1.000. LBbG is an opportunistic
species, exploiting these new food supplies and using new human
habitats (reclaimed areas and roof tops).
Input at the Belgian colonies initially came from abroad,
stimulated by immigration and good nesting habitat, especially the
expansion of the Zeebrugge harbour area. The vast sandy areas
became extremely suitable for nesting tern species and with
vegetation, for gull species as well. While Zeebrugge expanded the
industrial area, adjacent colonies in the Dutch Delta and along
the British coast reached their maximum and LBbG had to search for
new nesting places. In the Netherlands, numbers had been growing
already for a much longer period, now resulting in severe
competition for nesting sites and traditional colonies in the
dunes along the Dutch coast were heavily effected by predation of
Fox, forcing all gulls to start breeding at roof tops or to join existing
colonies at industrial areas. Similar problems with foxes have
been registered by Mike Marsh at Orfordness in Britain.
In the Netherlands, large areas of colonies have been claimed by
industry, increasing pressure on remaining colonies. Considering
these trends in nearby large colonies in Britain and the
Netherlands, the settlement of LBbG in Zeebrugge was hardly a
surprise.
Ring recoveries suggest LBbG originate from the colonies in the
Dutch Delta area (province of Zeeland, north to the mouth of Rhine
at Maasvlakte near Rotterdam) and from the British east coast of
the southern North Sea. Year 2001, 96 ringed LBbG were counted at
Zeebrugge, of which 27 were ringed as adult on the nest at
Zeebrugge in previous years. Others were ringed abroad:
27 from Europoort (Dintelhaven), the Netherlands, see map,
35 from Maasvlakte, the Netherlands, see map,
7 from Ordfordness, Britain, across the North Sea.
In previous years, a ringed LBbG from the inland industrial
complex of Moerdijk, the Netherlands was recorded as well.
However, remember ring reading may result in exaggerated figures,
as not all colonies have ringing programs.
The increase in subsequent years was stimulated largely by high
reproduction success of the colony at Zeebrugge itself. The average
breeding success may have been over 1.0 over several years.
In 2001, reproduction success of ringed LBbG was measured in 82
nests, which had one or both parents colour-ringed. The 82 nests
average 1.9
fledged juvenile per pair. This is extremely high and nicely
matches the doubling ratio of 99.4%.
Zeebrugge obviously is an attractive breeding place for LBbG. The
LBbG chicks diet completely existing of fish (12 regurgitations),
where Herring Gull also regurgitate food left overs from garbage
and birds (n = 12). LBbG hunt after fish on their own, or helped
by fishing trawlers, patrolling the rich fish-grounds of the
southern North Sea. The high breeding success in partly based on
low predation of LBbG in the colony of Zeebrugge. As said before,
the individual range of nests and the distance between nests at
Zeebrugge is much higher than the "completed" colony of
e.g. Maasvlakte. This figure is mirrored by predation on chicks
and eggs; at Maasvlakte predation on neighboring nests is a common
phenomenon, one of the factors diminishing breeding success.
future
Given these good breeding
results, one may expect to find an ongoing strong increase at
Zeebrugge. The LBbG growth rate for 2001 was an astonishing 126%.
For sure, the next years will show increasing numbers of breeding
LBbG as well. Further inland dispersion and settlements on roof
tops can be expected as well, as is already a trend in surrounding
countries.
Compared to colonies at Maasvlakte, the individual
territorial range at Zeebrugge is much higher (the Maasvlakte
colony being "fully occupied"), so a further increase from
abroad may be expected. However, as is nicely demonstrated at
Maasvlakte, these breeding colonies at industrial development
areas are highly vulnerable to tremendous loss of good nesting
sites as construction works may start, even within the breeding
season, resulting in loss of several 100's of eggs and recently
hatched chicks.
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LBBG 5cy
PP4, May 12 2001, Dintelhaven
Maasvlakte, the Netherlands. Ringed at the nest at Maasvlakte June 28
1997. |
LBBG 5cy EX07, May 12 2001, Dintelhaven
Maasvlakte, the Netherlands. Ringed at the nest at Maasvlakte June 21
1997. |
LBBG 5cy E558, May 12 2001, Dintelhaven
Maasvlakte, the Netherlands. Ringed at the nest at Maasvlakte June 15
1997. |
LBBG 5cy
EY84, May 12 2001, Dintelhaven
Maasvlakte, the Netherlands. Ringed at the nest at Maasvlakte June 24
1997. |
LBBG
4cy E056E, May 13 2002, Missouriweg, Maasvlakte, the Netherlands (51.59N, 04.02E). A local 4cy bird. |
LBBG
4cy E104E, May 23 & 31 2002, EMO, Maasvlakte, the Netherlands (51.59N, 04.02E). A local 4cy bird. |
LBBG
4cy E119E, May 12 2002, Naaktstrand, Maasvlakte, the Netherlands (51.59N, 04.02E). A local 4cy bird. |
LBBG
5cy E227E, May 16 2004, Dintelhaven, Maasvlakte, the Netherlands (51.59N, 04.02E). |
LBBG
5cy SA8, May 13 2002, Dintelhaven, Maasvlakte, the Netherlands (51.59N, 04.02E). Ringed at the Maasvlakte as pullus, June 20 1998. |
LBBG
5cy TT5, May 13 2002, Hartelhaven, Maasvlakte, the Netherlands (51.59N, 04.02E). Ringed at the Maasvlakte as pullus, July 08 1998. |
LBBG
5cy ACAJ, May 29 2003, Voorhaven, Zeebrugge, Belgium (51.59N,04.02E). Ringed at Zeebrugge as pullus. |
LBBG
5cy ADAF, May 29 2003, Voorhaven, Zeebrugge, Belgium (51.59N,04.02E). Ringed at Zeebrugge as pullus. |
LBBG
5cy AHAS, May 29 2003, Voorhaven, Zeebrugge, Belgium (51.59N,04.02E). Ringed at Zeebrugge as pullus. |
LBBG
5cy AMAK, May 29 2003, Voorhaven, Zeebrugge, Belgium (51.59N,04.02E). Ringed at Zeebrugge as pullus. |
LBBG
4cy L-82711, May 29 2003, Voorhaven, Zeebrugge, Belgium (51.59N,04.02E). |
LBBG
5cy L-89427, May 29 2003, Voorhaven, Zeebrugge, Belgium (51.59N,04.02E). No mirror on P10. |
LBBG
4cy L-92064, May 29 2003, Voorhaven, Zeebrugge, Belgium (51.59N,04.02E). |
LBBG
4cy L-92821, May 29 2003, Voorhaven, Zeebrugge, Belgium (51.59N,04.02E). |
Arrested
moult in sub-adults |
LBBG
sub-adult intermedius, Boulogne/Mer, NW
France,
May 17 2002.
Growing P8. |
LBBG
4cy graellsii T7PF,
Boulogne/Mer, NW
France,
May 01 2003. Arrested moult at P6. |
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