Paul Seligman sent in this article by Stephen Moss from the Guardian on 13th June.
For Britain’s breeding birds – especially those migrants that spend only a short time here before heading back to their winter home in Africa – June is a crucial month.
Plentiful sunshine – June is usually the sunniest month of the year in England and Wales, thanks to the long hours of daylight – provide the vast amounts of insects and invertebrates that these birds require to feed their young.
This sunlight-fuelled source of energy is crucial: if their youngsters are to be fit and healthy enough to make the epic journey south in the autumn, they need to get enough food during this time of plenty.
Some Junes bring perfect weather for aerial hunters such as swallows, martins and swifts. These species feed on the tiny insect plankton that hangs invisibly in the air on still summer days, so if June is cooler and wetter than normal – as in 2012, which was the dullest since 1909 – they struggle to find enough food for their weak and hungry youngsters.
For some species, this means disaster. Unless the weather improves, they will not have enough time to raise a second brood before autumn arrives. But the swift has a clever trick up its sleeve.
During spells of bad weather, these aerial acrobats fly hundreds of miles away to avoid getting soaked. Meanwhile their young enter a state of torpor, reducing their energy consumption so they can survive for days without food. Once the weather improves, the adult swifts return to the nest laden with insects, and resume breeding.