The sandy areas at the northern end of Castle Water are excellent for early bees associated with sandy habitats and over the last few years we have turned up a range of rare species from here including Grey-backed Mining Bee, Spring Colletes, Large Bear-clawed Nomad Bee and Yellow-shouldered Nomad Bee. The sand here is not a completely natural feature, being a by-product of the shingle extraction process of the 19th and 20th centuries. The ‘useful’ shingle was taken while the ‘useless’ sand was dumped creating the great drifts that we see today.
One of the reasons this area is so successful at attracting bees is that it is sheltered from the winds (particularly those cold north-easterlies in spring) giving that extra little bit of warmth. Warmth is important because bees being largely cold-blooded need to warm up before they can become active, forage, build nests etc. In addition, the warmer the ground the quicker will be the larval development, so additional heat may mean an earlier start and greater success. Sandy soil is also well drained, preventing physical flooding of nests and also the development of mould, though a certain amount of moisture is necessary to prevent the collapse of the nest tunnel and for larval development. These areas also have ample Sallow (and smaller amounts of Sloe) to provide nectar and pollen in spring for species which are active early in the year.
Grey-backed Mining Bee
Within those species which show a preference for sandy soil there are still differences. Sandpit Mining Bee, for instance, likes the very loose sand found on those areas which are trampled or driven on, and this constant disturbance is obviously very important in allowing this species to persist here. On the other hand, Spring Colletes and Grey-backed mining bee prefer the soil around the edges which is less disturbed and therefore more vegetated and firm.
Small Sallow Mining Bee
The less sandy areas increase the range of habitats available for bees, and other species of mining bee, such as Clarke’s Mining Bee and Small Sallow Mining Bee while liking well-drained soils to nest in do not necessarily need it to be sandy and in addition Clarke’s Mining Bee seems to be able to tolerate quite shaded locations as nest sites.
Around 75% of wild bees nest in the soil, so if you would like to attract some of these fascinating beasts to your garden, some good advice on how to provide habitat for ground-nesting bees can be found here https://ptes.org/wp-content/uploads/2019/05/How-to-make-a-habitat-for-ground-nesting-bees.pdf
Clarke's Mining Bee