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2018 August Nature Notes

Nature Notes

I shall focus on swifts today. These small almost black birds of the air should be familiar to all of us because they scream as they fly through and above the buildings of Uckfield and other European towns. They often breed in the roof of Holy Cross church and other tall buildings.

Swifts can live for more than 20 years, most of which is spent flying. Swifts are fast flyers and hold the record for maintained flight, often not landing at all for more than 10 months! They feed, drink, sleep and mate all while flying. When they want to sleep at night, they fly up to over 1000 metres above sea level and drift in the semi darkness sleeping as they fly, sleeping for short periods at a time. Then, when dawn breaks, they descend to the insect zone, where they snap up all the insects they encounter as they fly. Swifts are 100% dependant on insects and other invertebrates such as ballooning spiders for food.

The latter statement deserves explanation; ballooning spiders are small spiders which make gliders from the gossamer threads they use for webs. They then launch themselves into the wind and travel vast distances, but some are also snapped up by swifts and other birds.

Swifts arrive in Europe from the end of April to mid-May, find their nesting cavity, usually in a building and lay 2 or 3 white eggs in just one brood per year. Each egg requires about 19 days of incubation, this duty is shared by the male and female. Both parents collect invertebrates on the wing for their youngsters that take about 6 weeks to grow and mature before they are able to take their maiden flight, and are then independent, finding their own food on the wing as they fly with their parents in screaming flocks around the towns that they inhabit. They also fly off into the countryside searching out good places to catch flying insects and spiders. Most swifts will have left Europe by the end of August. They are among the last migrants to arrive on their breeding grounds and the first to leave.

Swifts spend the winter south of the Sahara Desert, flying around Africa finding food and water on the wing as they move to almost anywhere that insects can be found.

Dr.Martyn Stenning