19.
SALTMARSHES AND MUDFLATS
The inner firths within the Moray Firth are sheltered and there is little
wave action to disturb fine mud particles. The mud settles and forms mudflats
- large muddy areas often seen when the tide is out. Although they may look
empty of life, buried within the mud are great numbers of small animals such
as marine snails, worms and crustaceans. This is an important food supply for
shore birds and mudflats often provide valuable feeding and resting grounds
for many different species. They are especially important during the winter,
when feeding areas on land or in fresh water may be frozen.
The Moray Firth is an area of international significance for both wading birds
and wildfowl, supporting from 20,000 to 36,000 waders(41)
and 10,000 wildfowl(41), and the inner Moray Firth is recognised
as the most important sea duck(40) site in Britain. The
Moray Firth is therefore among the ten most important estuarine sites in Britain.
Many birds use the inner firths as migration staging posts, on their journey
south during the winter.
With so many birds descending on the firths, there is fierce competition among
them for food. However, worms, molluscs and crustaceans are not evenly distributed
in the mud, as some may live near the surface while others inhabit burrows deep
within the soft sediment. Birds have adapted in ways that enable them to exploit
different food sources and lessen the competition. Waders have beaks of different
shapes and sizes and are specialised for catching prey either on the surface
or at various depths within the mud.
Here are some examples of shorebirds and their adaptations for catching their
prey:
Curlew - the largest of the British waders, this bird has a long, curved bill
which is three times the length of its head. This bill, combined with the curlew's
long legs, enables it to probe deep into the mud for food in intertidal regions.
Lugworms are frequently eaten by
curlews - these worms inhabit burrows which can be up to 20cm deep so only
birds with long beaks can reach them.
Oystercatcher - the bright orange bill of this bird is perfectly shaped for
prising open shells of mussels and other molluscs. It may also probe the mud
for other intertidal creatures.
Redshank - this wader's long, red legs keep its body dry as it feeds in shallow
water. It also has a long beak and it chiefly feeds on worms, as well as taking
food from the mud surface.
Ringed Plover - a short-legged bird with a small beak, the ringed plover is
restricted to feeding on crustaceans and marine snails living near the surface
of the mud.
Turnstone - as its name suggests, this dumpy bird searches under stones for
crustaceans, molluscs and insects. Its short and slightly upturned bill is perfect
for flipping over stones.
In some places, a grass-like plant called eelgrass grows in the mud. This plant
is very uncommon in most of Britain, but can often be seen around the Moray
Firth. Eelgrass is an important food for wildfowl such as wigeon - a bird which
occurs in internationally important numbers in the Moray Firth.
In the summer, the inner firth's saltmarshes and coastal grasslands bustle with the nesting activity of waders, oystercatcher, curlew, knot, redshank, ringed plover and others. Large numbers of shelduck and eider duck also breed here, while ospreys catch flatfish in the shallow waters of the tidal flats to feed their young.
The Moray Firth is the most northerly major wintering area for waterfowl in Europe, with thousands of birds arriving in the autumn to spend the whole winter here. Geese, swans, ducks(40) and wading birds(41) arrive from Arctic Canada, Eastern Europe and Siberia. The best time to watch these birds is at low tide when tens of thousands gather in huge flocks on the apparently lifeless sand and mudflats - actually incredibly productive and rich feeding grounds. Excellent winter bird-watching sites include areas such as Nigg and Udale Bays, Loch Fleet(25) and Culbin sands(64). Care should be taken to avoid disturbing them as their feeding time is limited by the tide. As it rushes in, they're forced to retreat up the shore and then to leave in vast swirling flocks.