It is surprising how very early in the year spring starts for some species. We tend to associate spring with improving weather as March hopefully ‘goes out like a lamb’ and promising days of April, cheerful with yellow daffodils brightening our gardens and urban roadside verges. However, by that time many insects have already been very busy collecting pollen and nectar from even earlier flower sources.
Along the Mill-race the goat willows begin to flower during January. This is surprisingly early but the silver-grey male flowers, often known as ‘pussy willow’ soon turn butter yellow in February as they develop. This is because they are laden with yellow pollen and on fine days honey bees and other early flying insects such as their mimics, the drone flies, are encouraged out of hibernation to take advantage of this early source of food.
The drone flies are superficially very similar to honey bees and this mimicry gives them some protection from predators. Unlike the honey bee they have no sting but their shape and colour may make a hungry predator think twice before trying to eat them. Unlike honey bees they have huge compound eyes which cover much of the head but they only have one pair of wings. They are good pollinators and should be viewed as important as bees as pollinators of flowers and farm crops.
During the summer school children visiting the riverside to pond dip with the rangers sometimes catch rat-tailed maggots which are the larvae of these drone flies. The ‘rat-tail’ is a tube which breaks to surface of the pond to supply air to the developing larvae.
As spring advances a whole range of goat and grey willows and their hybrids, known also as sallows, come into flower and they are so attractive to insects that in sheltered locations such as on the Valley Trail an audible hum of can be heard as they work over the early blossoms.
These trees are particularly numerous on our riverside and as the spring months move towards summer several species of moth caterpillars feed on the leaves. This in turn attracts birds looking for lots of food for their growing broods. So the humble sallow is actually a very important tree and its value to wildlife should not be underestimated. It is also ideally suited to wet ground. It remains a small tree and when mature the limbs tend to fracture and fall about so it is, perhaps, not the best tree to plant where there are footpaths or fences but if left alone the fallen branches will readily root in damp ground.