Kagsmosen is a small protected bog that is squeezed inside by the motorway and buildings. In the 19th century, the swampy and difficult-to-penetrate area was part of the large fortification that encircled Copenhagen with Vestvolden, Utterslev Mose and the defense batteries in the north. Vestvolden lost its significance from 1920 and in 1939 they began to make Kagsmosen more audience-friendly and built paths. The area is now laid out as a park but has retained its character of bog with several peat digging lakes and canals. In certain areas, nature care is carried out for the benefit of animals and plants. Breeding waterfowl include Little Grebe, Red-necked Grebe, Mute Swan, Greylag Goose, Eurasian Moorhen and Eurasian Coot. The area also houses breeding Great Spotted Woodpecker, Long-tailed Tit, Fieldfare and Thrush Nightingale as well as many songbirds, including Reed Warbler and Marsh Warbler. In previous years, the relatively rare Penduline Tit has bred in the bog. Short-toed Treecreeper has been found breeding since 2012. Common Buzzard and Marsh Harrier breed in certain years. On Vestvolden up to the bog or in the bog itself, Sparrowhawk often breed.
Kagsmosen is also an excellent bird area for resting and migrating birds. Many ducks, geese and Common Teal, Northern Shoveler, Tufted Duck and Common Pochard can be seen and many of birds of prey. Especially Common Buzzard and also European Honey-buzzard, and occasionally Red Kite, Northern Goshawk, Rough-legged Buzzard, White-tailed Eagle, Osprey and Hen Harrier. Common Crane annually pass the bog. In addition, many species of waders, larks, swallows, pipers, thrushes, songbirds and finches migrate through the area. The winter season often offers a lot of ducks and Whooper Swan, as well as occasionally Goosander, herons, raptors and waterfowl. Apart from many different passerines, it is sometimes possible to see White-throated Dipper and in certain years flocks of invading Bohemian Waxwing. A few years ago Short-toed Treecreeper started to overwinter here. Common Kingfisher is a seldom but regular guest in the area.
In winter, you can visit the nearby locality Harrestrup Å, Islev (Marked with a star on the map), where especially the stretch between Brunevang and the motorway can show both Common Kingfisher, White-throated Dipper and Grey Wagtail.
It is easy to reach Kagsmosen by public transport. Bus 350S from Copenhagen stops at Herlev Hovedgade/Frederikssundsvej right next door. One can also take the S-train to Husum Station which is right next to Vestvolden and the bog. If you come by car you can park on Vindingevej near Husum Station.