Distribution and habitat
The dipper (Cinclus cinclus) is a bird that is found next to fast-flowing streams and rivers, mostly in upland areas of Scotland, Wales and north and south-west England. This is the bird that is also known as the white-throated or European dipper. Similar species are found in other parts of the world, such as the American dipper (Cinclus mexicanus) and brown dipper (Cinclus pallasii) of Asia.
Dippers are renowned for staying in the same place for year after year once they have found a suitable territory. The territories can also be “inherited” by future generations, such that there are records of dipper families inhabiting the same small stretch of river for more than 100 years. If you know where dippers can be seen, you can bring your children many years later and have a good chance of showing them the descendants of the ones you first saw!
Appearance
The dipper is a compact and somewhat plump bird, with a short bill and tail, the latter often held cocked upwards. In shape it is not unlike a wren, but it is considerably larger, at around 18 centimetres (7 inches) in length.
The plumage is dark grey, with some chocolate-brown colouring on the head and underneath, but set off by a brilliant white lower face, throat and chest (males and females have similar plumage). It is this white chest, seen in the subdued light that often accompanies tree-lined upland streams, that usually attracts the attention of the passer-by.
Feeding
The feeding behaviour of the dipper is what most birdwatchers love to see. The bird walks or dives into the water to gather food from the stream bottom, mainly invertebrates such as freshwater shrimps or insect larvae. They may also catch small fish. They use their wings to force themselves down against the current. Much of the food is swallowed under the surface, although they may bring larger items out of the water. Some food is also found on the banks of the stream or river, with stones being turned over to see what is underneath.
Breeding
Nest building takes place in April or May, with a suitable crevice being found that will hold nesting material. This could either be a natural gap between rocks (sometimes behind a waterfall) or a space in a wall or bridge. The nest may be relined for a second brood but not reused in successive seasons.
The crevice is filled with moss and vegetation that is either fetched from the bottom of the stream or dipped in the water before being added to the nest. The nest has a domed structure with a side entrance that points down towards the water. Both birds build the nest, which can take several weeks, with the female adding the finishing touches.
The clutch, of up to six eggs, is laid one a day and incubated by the female alone for up to 17 days. By only starting to incubate after the last egg is laid, all the chicks should hatch at roughly the same time. Both birds feed the chicks for up to 24 days in the nest and for a few days more after they have fledged. A second brood is usual, except in areas where food supplies are likely to be harder to come by, such as more mountainous regions. It is typical for the second brood to be started some ten days after the first brood has fledged.
Conservation
Dipper populations have declined in some areas of the United Kingdom but remain stable in others. The declines may be due to environmental factors such as acid rain and industrial pollutants which reduce the numbers of insects and invertebrates and cause eggshell thinning. However, in overall terms this is not a species that is regarded as being under threat.
Further information about the dipper, including an extensive audio clip of its call, may be found on this page of the RSPB website.
© John Welford
No comments:
Post a Comment