DMC#16: Amazing Aerialist
This is the 16th cache of a 20-cache circuit, consisting of 16 new + 4 existing caches adopted from Santos L Helper, which takes you anticlockwise through lovely mixed countryside from near Denton village across to near Middleton hamlet and back.
See DMC #1: Intro & Start for background info on the series, a map (also found in this cache's Gallery) and parking waypoints.
The cache, a 35mm film pot, is hidden near a gate at the side of Carter's Lane opposite a convenient parking spot - if wishing to do as a Park 'n' Grab.
As I was placing the cache, I heard the familiar (but increasingly uncommon) screeches of these extraordinary birds high in the sky above . . .
- Swifts (Apus apus) spend just 3 months of the year in Britain, arriving in early May and leaving in early August. This is shorter than any of our breeding birds except the cuckoo.
- They spend their winters well south of the Sahara: British-ringed birds have been recovered in the Congo Basin, Malawi, Tanzania, Zimbabwe, Mozambique and South Africa. However, the routes they use to and from these places are not (yet) known. A young swift, ringed in Oxford on 31 July, was killed in Madrid on 3 August, having covered 1,300km in three days! The longest lived swifts will travel some 4 million miles in their lifetime (8 x return trip to the moon!).
UK numbers are in disturbing sustained decline (see graph in Gallery) due to substantial decline in flying insects and loss of suitable nesting sites in the eaves of houses (eg. conversion of derelict buildings, more energy efficient impermeable houses)- Historically, swifts nested in holes high in large trees which they still do so in old Scots pines in Scotland’s Abernethy Forest. Today almost all swifts nest in colonies under the eaves of old buildings.
- They are long-lived birds (average 5.5 years, max. recorded for wild swift 21.1 years) , reflected in the fact that they lay just one 2-3 eggs clutch/year.
- They are monogamous and the same pairs breed in successive years. Whether pairs remain in
contact other outside the breeding season is not known.
- They are creatures of the air, feeding, mating and roosting on the wing, and are not thought to land between breeding seasons! They are also the fastest bird in the world in level flight reaching speeds up to 112 kph.
- Because they depend totally on airborne prey they are very susceptible to bad weather during the breeding season, when lack of food may mean chicks starving to death. Only most young birds, swift chicks can survive without food for up to 48 hours, lapsing into a semi-torpid state.
- Adults migrate south within days of the chicks leaving the nest.
Swifts feed at greater heights than swallows and martins and like feeding in unstable air to the rear of a weather depression, where there is often plenty of insects. Each bolus (ball of food) brought to chicks weighs just over 1g and contains 300-1000 individual insects and spiders.- Feeding birds will routinely fly great distances - British breeding birds have been found over Germany.
- They have tiny feet and almost no legs - adaptations to their aerial lifestyle. Adults can take off from flat surfaces, though rarely need to - juveniles find this difficult. At a month old, chicks do ‘press ups’ in the nest, lifting themselves up by pushing down on their wings, probably to strengthen the wings. By the time they’re ready to go, they can hold their bodies clear of the ground like this for several seconds
- They are unrelated to swallows or martins and their closest genetic relations are hummingbirds!
See here for more amazing swift facts.
See videos here (BBC AutumnWatch feature with great shots inside a nest), here (in flight preening - amazing slow motion shots) here (raising swifts) and here.
See here for an excellent short video on how to distinguish between the three hirundines (swallow, house and sand martins and the swift).