On Saturday's visit to RSPB Dungeness I saw many Swifts; too many to count. I also saw ca. 8 Hobbies. Hobbies are high speed raptors, that can capture Swifts, other bird and dragonflies on the wing. Both the Swifts and the Hobbies have only recently returned form sub-Saharan Africa.
There were few dragonflies out at Dungeness (as its a little too early for the appearance of most dragonflies) so perhaps the Hobbies were there in numbers because the Swifts were there in numbers.
When I relooked at my camera roll I think I may have capered a Hobby just about to capture a Swift in flight (but it is indistinct, because it was taken at a distance and the birds were moving fast).
Not many predators can catch a swift – hobbies may take a few, and so may kestrels, tawny owls and barn owls. However, it’s likely that many of the swifts they manage to eat were weak for other reasons eg starvation. Very few mammals ever catch one, except perhaps rats or weasels that can climb to nests. Amazing facts about swifts (rspb.org.uk)
Hobbies are among the most agile and acrobatic birds of prey. They are capable of catching fast-flying birds such as swallows and swifts in mid-air. Another important food source is dragonflies, which are also caught, and sometimes eaten, in flight. Hobby (Falco subbuteo) - British Birds - Woodland Trust
Hobbies hunting.
Hobbies hunting.
Here is a photo by Clive Newcombe, published in Pictured: The 'incredibly rare' moment a hobby falcon wrestles with its prey in mid-flight | Daily Mail Online 24.06.09 of a Hobby eating a Swift in flight.
Swifts will travel long distances to forage for aquatic insects. It is probable though that Brighton's Swifts are more likely to be foraging over closer waters, as the balance of calorie intake to energy consumption is important to survival; although Swifts in Northern Ireland have been shown to forage over 25 miles in nesting season.
Swifts at RSPB Dungeness
Their nemesis: A Hobby
It took me four hours to travel from my house (600m from the Swift Colony at Brighton General Hospital) the 66 miles to Dungeness by foot, train, bus, bus, and foot, yesterday (due to rail replacement busses). Swifts can fly up to 69mph; so a Swift could have got to Dungeness in an hour; it would take a Brighton Swift 6-7 minutes to get to the Adur Estuary to forage; which is the nearest supply of abundant aquatic insects. Swifts would beat me again, as it takes me 45 minutes on my bike to Shoreham.
A Hobby
Not that these time and distance comparison probably really mean anything to a swift, as swifts and humans live is different perceptual worlds, and perceive time and distance differently; we have different umwelts, as biologists put it. Humans think about time and speed; Swifts almost certainly don't "think" in clock-time, or "think" in amounts of distance; they experience the passage of time and distance through their senses. This is a topic I am looking forward to finding out more about
コメント