Environment A to Z of Canal Wildlife
A to Z of Canal Wildlife: A - C

Alder [Alnus glutinosa]

A very common canal side tree easily recognised by its black fissured bark and dull green broad, unpointed leaves, and in winter by its long attractive catkins, which hang like lambs tails, and dry seed heads which resemble small fir cones.

Although it will eventually form a medium size tree it usually occurs more as a clump at the waters edge. It is able to thrive here, where other trees would find it too wet, because its roots are able to form an association with bacteria which can utilise atmospheric nitrogen. There is little nitrogen in waterlogged soil so without this ability the Alder, like most plants, would find it difficult to grow. Indeed, the Alder actually ‘makes’ more nitrogen than it can use, so over time it builds up the fertility of the surrounding soil.

Alderfly [Sialis fulginosa and Sialis lutaria]

AlderflyThese dull brown insects are related to the snakeflies and lacewings and fly in early summer. They settle, with their wings held roof like over their bodies, in large numbers on canal side plants, including the Alder hence the name.

There are two species, both are poor fliers and only live about three weeks. There only role as adults is to mate and lay eggs. They usually never even feed! They lay about 500 eggs on plants and stones near the water. after 10 to 14 days the brown larvae hatch and enter the water where they live under stones or in the mud. They prey on other small water creatures and they themselves are eaten by fish. Those that survive take up to two years to grow to full size [2.5cm/1"long], then they leave the water to spend their three week pupal stage in mud and debris on land whilst they change into a flying insect ready to begin the cycle again.

(Bumble) Bees

BeeACRecent virus infections in the bee population (kept hives) have resulted in significant reductions in their numbers. The bumble bee has also been damaged and their numbers in recent years appear to have declined.

The Wilts and Berks (and similar environments) are increasingly important as they are varied in terms of animal and plant diversity. They are also relatively well preserved - some might say undiscovered - allowing more fragile species the time to recover at their own pace.

Brambles, Butterflies & Birds

BerriesThe bramble could be described as the canal restoration volunteer’s nightmare. Found all along the canal on bank and towpath hedge, where it can form an impenetrable barrier, its vicious thorns show no mercy to uncovered hands and arms. Also pendulous stems hang down from overgrown hedgerows to scratch the unwary walker’s face.

Nonetheless, the bramble provides a very important wildlife habitat supporting butterflies, birds and many types of insects.

Commonly found along the canal the blackberry (Rosaceae rubus fructuosus) soon establishes itself. it spreads as its long arching stems tip root into the soil, marching along colonising as it goes, and is itself colonised by countless insects and birds, a fine example of the interdependence between the canal side flora and fauna.

All parts of the bramble are a source of food. Insect life is abundant during the spring and summer. Sap sucking insects, aphids, soon invade the lush new growth.

The flowers provide nectar and pollen for other insects, especially for bees and hover-flies which in return provide a pollination service. The summer’s berries are food for the grubs of the many beetles and moths, for butterflies who suck up the juice from mushy berries and for wasps who puncture the berries to feed on the sugary contents. The berries are food for many birds including the blackbird who, by wiping off seeds from its sticky beak onto leaves and twigs, which are then washed to the ground by rain, spread the plants to canalsides new.

Even the leaves are food for, although they are protected by thorns, some animals who will still eat them, especially when they are young and the thorns have yet to harden. The moth, (Nepticula Aurella), exploits the bramble by laying its eggs on the leaves. When they hatch, the larvae burrow into the leaf to tunnel their way around between the upper and lower surface munching away and leaving behind a translucent trail until they finally emerge as moths.
Restoration volunteer’s nightmare? Well perhaps, but the bramble is certainly a wildlife haven and blackberries taste delicious to humans, and are free, but look out for those thorns!

Caddis, Carp, Catkin & Comfrey

There are almost 200 species of caddis-fly in Great Britain ranging in size from a tiny 6mm wing span up to largest, Phryganea grandis, at 60mm. some are well known, especially the sedge flies, as anglers use them for bait, others much less so. Some prefer fast flowing water, others the still waters of lake margins, ponds and canals. One, the common Glyphotaelius pelllucidus, is widely distributed near still water but rarely seem as although it flies in both early and late summer it hides during the day time amongst waterside vegetation and trees and unless disturbed appears only at dusk. They may be easily mistaken for moths, but closer examination will reveal that their wings are quite different, being membranous and hairy, not covered in scales. They also hold their wings differently, roof like over the body not flatly as moths do. The fly has only a short life, but time enough to mate and produce eggs. Some lay their eggs in the water either descending below the surface, or by dropping them as they fly, others fix eggs to overhanging vegetation and when they hatch the larvae drop into the water. The larvae of most species make tubes from grains of sand or bits of vegetation to protect their soft bodies and gills. This also acts as camouflage and it is this that gives the caddis fly its name, from caddis man, an old word for a peddler who wandered the countryside with samples of his goods adorning his clothes. As it grows the larvae adds more material. Most caddis-fly feed only on vegetation although a few do take other small water animals. After a series of moults it is fully grown and ready to pupate, it then seals up its shelter to keep out predators. When it is ready to change into the winged state the pupa uses its strong jaws to bite its way out and swim to the surface. It then emerges from the pupal skin and flies away to begin the cycle again.

Day time hiding places for the caddis-fly may include willow trees whose branches overhang the water or lower vegetation with large leaves like comfrey which grows in great swathes along the banks of the canal. Its flowers, which vary from white through pink to mauve and purple, from May to September are great favourites for many insects and on warm days attract masses of bees.

CarpPredators of the caddis-fly include the carp who although mainly vegetarian do take worms and insects. the carp is widely distributed and grows well in man made still waters especially if densely weeded up like poorly maintained canals. Carp vary in colour from brown-green to blue-green upper parts with blue-green to straw coloured sides. A mature adult can reach 0.5 metres in length, and some up to 40 lbs. in weight have been caught, so they are popular with anglers.

CarpSeveral trees and shrubs commonly found along side canals bear catkins in the late winter and early spring time. Alder, hazel, birch and most notably the willow family burst into flower early before the leaves emerge. The flower spikes of the willow are so called because they are made of fine hairs, hence the likeness to a little cat, or catkins. Goat willow is known as pussy willow because of its fluffy male catkins. The long male flowers of hazel are called lambs tails because of the way the catkin hangs, like a lambs tail. The showy catkin we recognise is almost always the male flower, although there are exceptions the female is usually small and insignificant. The pollen is carried from the male catkin to the female by the wind so there is no need to attract insects hence the flowers lack bright petals.
Some, like the hazel, have both male and female flowers, others carry all the same sex. The grey leafed willow has golden catkins on the male tree and silver catkins on the female. When fertilised the female flower develops throughout the summer into a seed pod. The one most easily recognised is the nut of the hazel, known as cob nuts they provide food to many of the small animals that live beside the canal.