Brownfield sites. Eyesore or haven for wildlife?
When visiting a brownfield site, to many people it appears uninviting, boring and perhaps an eyesore. They could probably also think that wildlife has the same views as them. They could be well far off the mark. I visited this site on the 14th March 2014 at Salford. It did look boring, to be honest, and many people were simply walking through the site and not taking any notice of what they were walking past. It was once a housing estate with roads, houses, high rise flats (possibly Kersal Flats) and not too far from the River Irwell. I saw that just one large, pussy willow tree, (Salix caprea) had managed to grow amongst the rubble, concrete, tarmac and patches of vegetation, grasses, and dare I say weeds?!
The tree was a hive of activity. It was like a magnet for the many queen bumblebees that were foraging on the numerous pollen laden catkins with many busy to-ing and froing. I looked on the ground and saw at least 6 bumblebee queens of several species, all covered in pollen. Some were simply resting with others crawling in and under the dead leaves. No doubt there were many others doing just the same. With some foraging and flying away and others resting on the ground, why was this I thought? Perhaps the foragers were collecting pollen to start nests and the resting ones had recently emerged from hibernation and this was one of their first meaningful meals, or even their very first. Unfortunately, I did not have the time to stay and ‘explore’ any further.
Why were the bees so busy here? Willow is a sallow. Whilst researching for this piece I came across this excellent article by Prof. Dave Goulson, “The best garden flowers for bees”, in which he states “Sallows are dioecious, being either male or female. Both produce catkins in early spring and are very important sources of food for queens. The males produce pollen and a little nectar, the females only nectar. Dwarf varieties can be bought for smaller gardens.” In his book, he states “The nest establishment phase in spring when the queen has to single-handedly gather sufficient forage to feed her first batch of offspring may be the time when the availability of flowers is most vital.”
There were not that many flowers around then in flower that could provide the pollen requirements needed by the queens and all in one place From a single willow tree, not having to diligently search here, there and everywhere would indeed be a real bonus. Alford states that ” Pussy and common willow are important sources of nectar (male catkins are also excellent producers of pollen) and large numbers of overwintered queens may be attracted to them. The scarcity of spring forage has a deleterious effect on the survival of overwintered queens.” No wonder the bumblebee queens were so busy at this one willow.
Forage in gardens
Most of us though have not got the garden space to plant a willow. However, we may have the space to grow a Kilmarnock dwarf willow and I absolutely recommend these trees. If not you may be able to grow these early spring flowers near their nests.
If we as gardeners and our neighbours all planted high-quality spring and summer forage in our gardens for bumblebees, they would not have to forage at a further distance. Carvell et al states if colonies were placed within 250-1,000 meters of high-quality forage for spring and summer it was hugely beneficial for them. It helped by producing more queens that can found new colonies when they emerge from hibernation.
Besides my own observations, website links as above, Refs and further reading:
Alford, D. V. (1975) “Bumblebees”.
Lovely article here Spring Bumblebees by Brigit Strawbridge;
Soil Association organic herbaceous perennials and alpines try Caves Folly
Kersal flats website click on Today for some wonderful photos of the area in question esp number 4
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