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The site was identified as internationally important for bird conservation in 2000 because it was regularly supporting significant populations of the species listed below, meeting ('triggering') IBA criteria.

Populations meeting IBA criteria ('trigger species') at the site:

Species	Red List	Season (year/s of estimate)	Size	IBA criteria
Whooper Swan Cygnus cygnus	LC	non-breeding (1994)	941 birds	A4i, B1i, C2
Tundra Swan Cygnus columbianus	LC	non-breeding (1993)	332 birds	A4i, B1i, B2, C2
Brent Goose Branta bernicla	LC	non-breeding (1994)	6,800 birds	A4i, B1i, C3
Barnacle Goose Branta leucopsis	LC	non-breeding (1997)	30,000 birds	A4i, B1i, C2, C6
Common Shelduck Tadorna tadorna	LC	non-breeding (1994)	6,500 birds	A4i, B1i, C3
Northern Pintail Anas acuta	LC	non-breeding (1994)	900 birds	B1i, C3
Pied Avocet Recurvirostra avosetta	LC	breeding (1994)	248–482 pairs	B1i, B3, C2
Pied Avocet Recurvirostra avosetta	LC	passage (1994)	1,300 birds	A4i, B1i, C2
Eurasian Golden Plover Pluvialis apricaria	LC	passage (1994)	25,000 birds	A4i, B1i, C2
Bar-tailed Godwit Limosa lapponica	NT	passage (1994)	4,600 birds	A4i, B1i, C2
Black-tailed Godwit Limosa limosa	NT	breeding (1994)	110–125 pairs	B2
Red Knot Calidris canutus	NT	passage (1994)	21,300 birds	A4i, B1i, C3
Dunlin Calidris alpina	NT	passage (1994)	62,000 birds	A4i, B1i, C3
Spotted Redshank Tringa erythropus	LC	passage (1994)	1,270 birds	A4i, B1i, C3
Black Tern Chlidonias niger	LC	breeding (1994)	36–41 pairs	C2, C6
A4iii Species group - waterbirds	n/a	non-breeding (-)	20,000-49,999 birds	A4iii, C4
A4iii Species group - waterbirds	n/a	passage (1994)	100,000-499,999 birds	A4iii, C4

Ideally the conservation status of the IBA will have been checked regularly since the site was first identified in 2000. The most recent assessment (2010) is shown below.

State (condition of the trigger species' populations)
Species	Actual vs Reference (units)	% remaining	Result
Greylag Goose Anser anser	6,000 / 6,700 (birds)	90	moderate
Grey Plover Pluvialis squatarola	2,100 / 3,600 (birds)	59	poor
Charadrius alexandrinus	5 / 23 (birds)	22	very poor
Black-tailed Godwit Limosa limosa	101 / 242 (pairs)	42	poor
Ruff Calidris pugnax	0 / 87 (pairs)	0	very poor
Dunlin Calidris alpina	0 / 9 (pairs)	0	very poor
Little Tern Sternula albifrons	1 / 12 (pairs)	9	very poor
Arctic Tern Sterna paradisaea	13 / 133 (pairs)	10	very poor
Short-eared Owl Asio flammeus	0 / 2 (birds)	0	very poor
Bluethroat Luscinia svecica	50 / 50 (pairs)	100	good

Pressure (threats to the trigger species and/or their habitats)
Threat	Timing	Scope	Severity	Result
Agricultural expansion and intensification	happe­ning now	most of popul­ation/area (50–90%)	moderate decline (10–30% over 3 gener­ations)	high
Other	happe­ning now	most of popul­ation/area (50–90%)	moderate decline (10–30% over 3 gener­ations)	high
Invasive and other problematic species and genes	happe­ning now	most of popul­ation/area (50–90%)	moderate decline (10–30% over 3 gener­ations)	high
Human intrusions and disturbance	happe­ning now	most of popul­ation/area (50–90%)	moderate decline (10–30% over 3 gener­ations)	high

Response (conservation actions taken for the trigger species and/or their habitats)
Designation	Planning	Action	Result
Most of area (50–90%) covered (including the most critical parts for important bird species)	No management plan exists, but the management planning process has begun	Some limited conservation initiatives are in place	low

Year	Protected Area	Designation (management category)	% coverage of IBA
1980	Kiers Gård Margrethe Kog	Fredet ved afgørelse, exl. Kirkeomgivelser (V)	<1
1985	Margrethe Kog	Fredet ved afgørelse, exl. Kirkeomgivelser (IV)	19
1988	Tøndermarsken Statsfredning	Fredet ved afgørelse, exl. Kirkeomgivelser (IV)	38
1992	Tønder Kommune	§3 beskyttet natur (alle søer, moser, vandløb, heder, enge mv) (IV)	16
2009	Vadehavet med Ribe Å, Tved Å og Varde Å vest for Varde	Marine Protected Area (OSPAR) (UA)	5

Habitat	% of IBA	Habitat detail
Artificial/Terrestrial	70
Marine Coastal/Supratidal	15
Marine Intertidal	15

Land use	% of IBA
agriculture	85
nature conservation and research	15

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Recommended citation
BirdLife International (2024) Important Bird Area factsheet: Tøndermarsken, Magisterkog and Rudbøl Sø (Denmark). Downloaded from https://datazone.birdlife.org/site/factsheet/tøndermarsken-magisterkog-and-rudbøl-sø-iba-denmark on 23/12/2024.