Ynglefugle i Vejlerne - Dansk Ornitologisk Forening

222 Ynglefugle i Vejlerne
Baillon's Crake has been heard a few times in Vejlerne
in June-July, with a total of six different birds between
1982 and 1998. Vejlerne is far away from any regular
breeding site of Baillon's Crake, and the recorded birds
most likely represent single individuals on extended migration.
Corncrake. Prior to 1999 Vejlerne and their surroundings
were of marginal importance for Corncrakes, but
in 1999 a sudden increase in numbers recorded were
observed in Vejlerne as well as in the rest of Denmark.
After 1999 up to 14-16 territories have been mapped in
the vicinity of Vejlerne each year. All birds have been
recorded in cereal elds. The 1999 change is probably
related to a period with recession in Eastern Europe,
where former farmlands have been given up, and temporarily
provided suitable conditions for breeding Corncrakes,
and birds originating here have been spreading
westwards to Denmark including Vejlerne. It is however
most likely only a matter of short time before they
will disappear again, because suitable habitats, i.e. extensively
cultivated meadows without grazing and with
late hay-cutting, are rare in Vejlerne and nearby agricultural
lands.
Moorhen has always been a regular but less numerous
breeder in Vejlerne. The species has been monitored by
mapping, and there is no obvious trend in the numbers
recorded (Table 32). The numbers neither represent true
population sizes, because Moorhens due to their discreet
behaviour are very difcult to count in the reeds
and bulrushes surrounding the shallow lakes they prefer.
The true population could easily be around 100 pairs,
and is most likely only of marginal importance at the
national scale.
Coot most likely was one of the rst waterbird species
that colonized Vejlerne after the embankment, because
they would probably settle as the rst bank vegetation
developed on the lakes. Ever since the Coot has been a
characteristic element in the lakes and ponds of Vejlerne.
It has not been possible to make any comprehensive
survey of breeding Coots, because many nests are hidden
in the reedbeds. In a small sampled area more than
100 nests have been recorded several years. The total
population of Coot in Vejlerne could well be 1000 pairs
or more, and probably represents about 5% of the total
breeding population in Denmark. Irrespective of the
missing details on population size, Vejlerne remains a
very important breeding site for the Coot.
Crane. Historical sources do not mention Vejlerne as a
breeding site for Cranes. Almost annual observations of
single pairs in the breeding period since 1991 therefore
represent a recent colonization. Observations in 1993
and 1996 suggested true breeding attempts. After 2000
more attempts have been recorded, and the rst successful
single pairs with unedged chicks were recorded
in 2002 and 2003. After the Field Observatory was
closed in 2003, 2-3 breeding pairs have been recorded
in Vejlerne 2004-2006, and some of them bred successfully.
The establishment of a local breeding population
in Vejlerne happened in conjunction with a massive increase
of the Danish breeding population, from 3-4 pairs
in 1990 to 40-45 pairs in 2003. The expansion is most
likely caused by improved protection of the breeding
sites, and more efcient protection against hunting and
improved feeding conditions in the wintering quarters.
The breeding habitats used by Cranes in Vejlerne are
distinct from the traditional Danish breeding sites, where
they breed in moors on nutrient-poor coastal heaths; in
Vejlerne they breed in wet reedbeds. After the breeding
season a major part of the Danish population stage in
Vejlerne in autumn, and the numbers have been steadily
increasing, reaching a peak of 113 in autumn 2003.
Oystercatcher has breed in Vejlerne since the rst ornithologists
visited the area in the early 20 th Century.
Judged from counts conducted prior to the Field Observatory
period, numbers had been declining at Bygholmengen,
and this probably happened in response to a change
in salinity on the meadows after the new sluice was
built in 1965.
In 1978-2003 the population has varied between 54
and 91 pairs, usually 70-80 pairs. The uctuations have
been dominated by numbers found on Bygholmengen
that on average held 44% of the population (Fig. 51). A
remarkable increase in numbers in 1997 might be explained
by an extraordinary intake of brackish waters from
the Limfjord that was carried out this year.
Oystercatchers of Vejlerne only represent a marginal
proportion of the Danish population. The species has
different and in fact often contradictory requirements to
the breeding habitat than most of the waders breeding on
Bygholmengen, some of which are rare and endangered.
Therefore management habitats for Oystercatchers in
Vejlerne should be given less priority than management
for other meadow birds.
Stilt has not been observed as a potential breeder in Vejlerne
in the study period 1978-2003. A single pair tried
to breed in 2005 in the northern end of Bygholmengen.
The pair defended a nest but gave up breeding after 7 th
of June. This was the second conrmed breeding attempt
in Denmark.
Avocet has probably bred in Vejlerne continuously since
the embankment, because the birds' habitat preferences
would have been met even before the meadows grew
up. In 1964 the population counted c. 400 pairs at Bygholmengen
and 30 pairs in Vestlige Vejler, but later the
population declined in response to the lowered water
level resulting from the newly built sluice (Centralslusen)
in 1965.
The population after 1978 has uctuated quite a lot,
but with an increasing trend in numbers (g. 52). The
highest numbers were recorded in 2001 with 690 pairs,
but the following years the population declined rapidly.
Bygholmengen has been the dominant breeding site with
90% of all recorded pairs.