A few miles north of Heathrow airport and within earshot of the M25, the river Colne forms the boundary between Buckinghamshire and north west London; it is a small chalk river with clear, shallow water and wide gravel beds, lined by tall, ivy-clad trees.
The sheltered margins and banksides are bright green with patches of invasive, floating pennywort. The woods ring with the calls of introduced ring-necked parakeets loudly defending nest holes from one another. This is a habitat squeezed at the edge of the capital and much degraded due to its unfortunate geography.
The river is bordered by flooded gravel pits, and, where the water meadows have not been built on, patches of remnant parkland where red kites sit in beautiful, ancient trees and whistle their wistful calls. These are descendants of a recently introduced population established in the Chiltern Hills; part of a programme to bring back kites to all parts of the UK. A pair fly together and one stoops to pick up something from the ground and then again; it is probably a male showing off his hunting prowess. Others circle high over the gravel pits and one suddenly stoops at and just misses a flapping, twisting magpie low over the open water.
Next to the Colne is Little Britain Lake, so named because the shape resembles the outline of the British Isles. The lake is lined with footpaths and fishing stands and evidently is a popular spot. Lots of mallard, gadwall and tufted ducks brightly lit by the winter sun, idle on the calm water, always keeping a safe distance from the edge; also a single great crested grebe, pairs of mute swans, Canada and greylag geese; fighting coots and a few moorhens. Black headed gulls sit together on branches and erupt over the water for no reason. Many of the waterbirds, especially the geese, mallard and gulls lose their reticence and swarm at the first sign of a piece of thrown bread. Grey herons ‘krank’ loudly from atop huge stick nests that comprise the small heronry in the tall trees on the central island, they stand hunched, unimpressed with all around and appear to be attended by dark-suited retainers, cormorants that hang out to dry, sit and preen.
The first snowdrops are carpeting the otherwise bare, riverside woodlands. Small birds pass through in noisy flocks and include treecreepers and coal tits. Pairs of blue and great tits are investigating nest sites. Grey wagtails are on the river, either on the gravel margins or bobbing on rafts of pennywort near the small weir and a kingfisher is always evasive and sometimes on the undisturbed wet ditches within the water meadows. The crows are noisy in the treetops and a female sparrowhawk dives at one, perhaps not hunting but moving the pair from her nesting territory on the small island.