The Skylark (Alaudidae) is more likely to be heard before you see it.  You can here its continuous song as it climbs higher and higher into the sky over the fields of the Pelhams.  Keep watching as it often 'parachutes' slowly down suddenly plummeting very fast to the ground for the last few metres.

As you can see from my photo it is a small brown bird, somewhat larger than a sparrow but smaller than a starling. It is streaky brown with a small crest, which can be raised when the bird is excited or alarmed.  The outer edge of the tail is a conspicious white  and the wings also have a white rear edge, visible in flight. Its recent and dramatic population declines make it a Red List species.

Why do Larks do all this singing?  Well it's a matter of claiming territory - I caught these two Skylarks disputing their patch.

Skylarks clashing over territory

This is serious stuff!