Monday 19 November 2012

The Tawny Owls had returned to the beech tree, and were clearly visible though not perfectly placed for a picture.

The pair were sitting close together. They are beginning to take more notice of each other as the breeding season approaches.

A Carrion Crow was having a bath in the marble fountain in the Italian Gardens. This basin combines the features of a shower and a jacuzzi, and might have been designed as a bird bath.

Sadly, the other bathing place, right at the other end of the lake at the top of the waterfall in the Dell, has been ruined by gardeners ripping out the berberis and cotoneaster bushes that were inhabited by Goldcrests, and gave many small birds shelter when they came out for a bath and a drink. It is now bare and open and provides no cover at all.

Also at the bottom end of the Serpentine, the youngest Great Crested Grebe was unfolding a yellow-edged leg from under its wing.

It is remarkable how compactly grebes' long legs can fold up. Little Grebes, which have even longer legs in relation to their size, have to add one more fold by turning their feet backwards. All grebes find that their legs get stiff and cramped in this position, and you often see them stretching their legs out straight to ease them.

Grebes' legs are so highly adapted for swimming that the bones are flattened. This both makes the leg more streamlined as it cuts through the water, and gives it extra strength along the axis of the slashing sideways swimming stroke that gives its individually lobed toes the effect of turbine blades. This adaptation has occurred twice. The first bird to evolve similar legs and feet was Hesperornis, a seabird of the Cretaceous era that flourished 80 million years ago. It was bigger than any grebe and flightless, and seems to have had a similar way of life to modern penguins. This skeleton is of the largest species, H. regalis, which was 6 ft long.

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