Pills, Pools and Marshes - Gower - page 234

Savi's warbler Locustella luscinioides and aquatic warbler Acrocephalus paludicola . Cetti's warbler Cet-
tia cetti wasfirstrecordedin1977andrapidlyestablishedabreedingpopulationofupto20singingmales
each year, making Oxwich the Welsh stronghold for this species.
Marshes such as Oxwich are superb, but often overlooked, habitats for small mammals and support
a rich variety of species, with shrews being particularly abundant. The open habitats dominated by reed
havebeenshownelsewheretobeespeciallygoodforwatershrewsandevenharvestmice,boththesespe-
cies being unaffected by the presence of standing water. Harvest mice in fact are often the most abundant
small mammal in wetlands. They have even been found in the emergent vegetation in open water and
have been considered as the mammalian equivalent of the reed warbler. The distribution of harvest mice
in Wales is very patchy, and they seem to be most frequently recorded in purple moor-grass grassland on
bogs, but as a species it is easily missed. The first Gower record for harvest mice, in 1980, confirmed
this liking for purple moor-grass, when harvest mice nests were found in tussocks of the plant on dune
grassland adjacent to the reedbeds at Oxwich. The same year nests were also found in purple moor-grass
on Cefn Bryn. There are estimated to be about 10,000 animals in Wales along the coastal strip, but while
water shrews and water voles can often be seen amongst the reeds or swimming across the dykes at Ox-
wich, there are no records of harvest mice. Sadly the nesting site at Oxwich was burnt by vandals in the
mid-1980s and this may have destroyed the local population before the animals had a chance to colon-
ise the marsh. As harvest mice are clearly present in the peninsula it would be worth carrying out some
surveys of the marsh to establish if they are using this habitat. If they are found there may be a conflict
for naturalists, however, as recent research has shown that bitterns, once thought to feed only on fish and
amphibians, often eat small mammals, and that both water shrew and harvest mouse are a frequent food
item.
The floating fen developed as a result of plants colonising the mat of iris and bulrush, which grew
out across the surface of the flooded grazing land. This makes it delicate, easily damaged and in places
very treacherous, as the thin mat can easily be broken. Although the areas of floating fen at Oxwich are
small, they are rich and fascinating places for wildlife, especially plants. In spring the area is carpeted by
marsh-marigold, followed by numerous other species, including southern marsh-orchid, skullcap Scutel-
laria galericulata , gipsywort Lycopus europaeus , marsh lousewort Pedicularis palustris , yellow iris and
the poisonous hemlock water-dropwort. Bog-bean and marsh cinquefoil grow in the wettest parts on the
edge of open water and there are scattered clumps of the rather local lesser bulrush Typha angustifolia .
The animals of the fen have been little studied, but it is probable that there is a rich variety of inverteb-
rates. Snipe use the fen extensively in the winter, although few other birds appear to feed, roost or breed
there.
Wherethegroundisdrier,foratleastpartoftheyear,duetothewatertabledroppingorbecauseplant
litter has raised the ground surface, bushes and saplings have colonised the marsh. These damp winter-
flooded woodlands, known as carr woodland, are dominated by alder and willows Salix spp. As they are
a transitional habitat they are characterised by a mixture of plants from both wet and dry areas, including
water mint, common marsh bedstraw Galium palustre , meadowsweet Filipendula ulmaria , bracken and
herb Robert Geranium robertianum . Flocks of small finches, mainly chaffinch Fringilla coelebs , gold-
finch,siskin Carduelis spinus andlesserredpoll Carduelis cabaret ,feedinthetopsofthealdersinwinter,
extracting seeds from the small cones. In summer the bird community of the woodland is dominated by
willow warblers Phylloscopus trochilus and wrens Troglodytes troglodytes , which nest low in the under-
growth.Thescatteredbushesarealsoimportantsourcesofinsectfoodforreedwarblersandprovidesong
posts for reed buntings and willow warblers.