This month look out for solitary bees. 90% of Britain’s 250 UK bee species are solitary and like the social bumble and hive bees, solitary bees are very important pollinators of plants. Darwin carefully observed bees and other plant pollinators, correlating the length of the insect proboscis with their ability to reach nectar supplied by the plant, because this is important for the successful transfer of pollen between flowers. Solitary bees do not live in groups with a queen attended by workers, like other bees. The single females, after mating, make a nest where they lay eggs, 1 in each cell. They provide the eggs with a store of nectar and pollen, then leave. Look out for:- Tawny Mining Bee (Andrena fulva) a solitary bee that is an important pollinator of fruit trees in spring and the two-coloured Mason Bee (Osmia bicolor) which sometimes nests in snail shells.
25% of UK bee species are listed as endangered. To find out more, and how to attract some of these beneficial insects to your garden go to www.foxleas.com
During April and May look for trees and shrubs in flower. Many have very pretty flowers and attractive fruit in the autumn which provide food for birds. Look for the pendulous flowers of sycamore which are pollinated by bees. The flowers are either male or female, but both can be found on the same plant. Beech also has separate male and female flowers on the same tree. The male flowers hang in small clusters, like pom-poms, (note the stamens in the photograph), with sepals but no petals, while the female flowers are like bristly green balls. Why not plant a hedge of native species in your garden? As well as being very beautiful they also support a greater variety of minibeasts, birds and endangered bats than cultivated plants.
Swallows and House Martins
These birds return to the UK in April, but are more commonly seen this month. Their migration from southern Africa is triggered by changes in day length and is associated with the decrease in insect food in the overwintering site. Although they have no way of knowing the weather at their destination, the date of their arrival in the UK is related to temperature and the availability of flying insects along the route. If food supplies are restricted they will slow their northward journey. Both swallows and house martins are declining in numbers in the UK. Factors involved include decreased numbers of flying insects and reduced nesting sites. Please do record any sightings on the 'Record Your Sightings' page.
In connection with the migration of swallows from Britain in autumn, Darwin wrote:
"At the proper season these birds seem all day long to be impressed with the desire to migrate; their habits change; they become restless, are noisy and congregate in flocks. Whilst the mother-bird is feeding, or brooding over her nestlings, the maternal instinct is probably stronger than the migratory; but the instinct which is the more persistent gains the victory, and at last, at a moment when her young ones are not in sight, she takes flight and deserts them."
Like swallows and house martins, bats have suffered in recent times from the decrease in invertebrate prey and roosting sites. Their echo-location system makes them superbly adapted to catch insects on the wing at night. To find out more about bats, look out for bat walks this summer, advertised in Bromley's Walks, Talks and Events leaflet.