In article , Martin Gregorie
writes
On Sun, 25 Apr 2004 08:00:04 -0700, Eric Greenwell
wrote:

I know! A trained flock of small soaring birds that you release when
desperate. They spread out over the area, circling when they find lift.
Once you start climbing, they return to the glider and crawl back
inside, ready for the next time you need their assistance.

A month or so ago there was a nice piece on BBC Radio 4 about a hang
glider pilot who had a hen harrier that was trained to fly with him
and even to sit on a perch on his glider. He said that when lift was
strong he'd launch and gain height before letting his raptor fly with
him, but in weak, dodgy conditions the bird was flown first. He'd
launch and join her once she'd found a thermal.

In the biography of Hanna Reich there was a story that the
German team who took some gliders to S America in 1937 used to join the
local vultures in thermals.
They decided it would be a good idea to take some home to
Germany so they could leach on to them there. But when the ship got to
Bremen, the vultures had got so fat and heavy they couldn't get
airborne.
--
Mike Lindsay