I always think that winter begins to bite around the second week on November and there are of course many obvious indicators to remind us that our coldest season in waiting in the wings.

The clocks have gone back; we've had our first frost; autumn leaves fall thick and fast; Halloween has tricked and treated us and although bats have gone back into hibernation, spooky spiders are still sitting on glistening webs.

One of my favourite 'indicators' of impending winter concerns the nightly roosting flights of jackdaws, a bird whose population has really taken off in recent years.

From early autumn and throughout winter and well before dusk, every afternoon jackdaws fly fast and direct just above rooftops along a narrow corridor which takes them over my house, over Wimbledon town centre thence across Morden Hall Park towards Beddington and their mass roost.

They fly in twos, thirty, fifty and perhaps hundred strong flocks 'chak-chaking' to one another to keep in contact. I can almost set my watch by them, so regular are the flights.

The next morning shortly after sunrise a reverse flight takes place but rather more fragmented and with less urgency.

Meanwhile, above them gulls fly in a more leisurely fashion in the opposite direction to their roosting sites on west London reservoirs and back again next morning to forage on grassy areas playing fields and parks.

Presumably those same jackdaws(pictured) have spent their day in safe wooded areas of Richmond park and Wimbledon common so what urge drives them to fly so far to roost I wonder?