This Starling bringing food to its nest in the eaves of the shelter on Buck Hill couldn't go down to the nest because a Carrion Crow was watching it, and to go in would give away the location. So it stood on the roof and scolded the crow. Eventually the crow left in its own good time.

The bold Blackbird followed me round the Long Water again and collected a remarkable quantity of sultanas.

There was a young Blackbird on the lawn between the Dell and the Rose Garden. It was already foraging for itself.

A Wood Pigeon ate the flowers in a herbaceous border in the Rose Garden.

A Jackdaw looked for worms and insects in the long grass in the Meadow, the wildest part of Hyde Park near Marble Arch.

There was a Little Owl in the usual oak tree near the Albert Memorial.

An Egyptian Goose stood on a dead tree nearby, an easy place for a large bird to land.

The solitary Greylag gosling was at the Dell restaurant, perilously close to the hunting ground of the pigeon-eating Lesser Black-Backed Gull, but its parents were watching attentively.

There are no so many Coots on the lake -- about 220 -- that there is huge pressure on them to find nest sites. There were three nests in silly places on the edge of the Serpentine within 200 yards of each other.

Whatever misfortune caused a pair of Great Crested Grebes to fly up to the Round Pond also hit the nest under the willow tree near the bridge. It had three eggs in it which are now gone. The resident pair were hanging around nearby. There is plenty of time for them to nest again, and in fact if they wait until midsummer when there are more small fish they will have a better chance of success.

A Grey Heron knocked another one off the roof of one of the small boathouses.

Walking along Mansfield Street, W1, today I noticed this blue plaque.

It commemorates the ingenious Lord Stanhope whose inventions included a novel propulsion system for steamships. It was known that the existing paddle-wheel system was very inefficient, and he believed he had a better idea. It is recorded  in T. Baker's vast and almost forgotten epic poem The Steam-Engine:

Lord Stanhope hit upon a novel plan
Of bringing forth this vast Leviathan
(This notion first Genevois' genius struck); (1)
His frame was made to emulate the duck;
Webb'd feet had he, in Ocean's brine to play; (2)
With whale-like might he whirl'd aloft the spray;
But made with all this splash but little speed;
Alas! the duck was doom'd not to succeed!

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1. I can't discover who Genevois was.

2. Mr Baker was criticised for the ambiguity of this passage, in which it is not clear whether the 'webb'd feet' belonged to Lord Stanhope's experimental ship or to Lord Stanhope himself. In 1858, after the poem was published, Lord Stanhope's butler, a Mr Banks, felt compelled to defend his late master in a letter to The Times: 'His Lordship's feet and frame were most agreeably formed, and pefectly adapted to meet every obligation of the high rank and privilege to which it pleases God to call an English nobleman.'

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After the abandonment of this project, a far better solution was found in what Baker called 'Rennie's conoidal triple-bladed screw' -- that is, the familiar propeller used today. It was invented by George Rennie (1791--1866), the son of John Rennie the Elder who designed the Serpentine Bridge.

In fact even for birds the web-footed propulsion system is not very efficient. Some birds, such as cormorants and loons, can manage decent underwater speeds with it, but grebes have a much better system: their three large fringed toes have the same shape as propeller blades and are slashed sideways through the water, giving more speed for less effort.

This video made a year ago has a brief sequence of a grebe swimming under water at its normal cruising speed, about 5 mph, seen from above. But they can go at least twice as fast as this if they need to.

I also saw this notice in the Bayswater Road, but sadly not the bird it mentioned.