The large roost gatherings of rooks, jackdaws and crows are one of the highlights of winter wildlife watching.Some roosts involve many thousands of birds, coming from large areas of the surrounding countryside.
Before sunset birds start to gather nearby to the roost trees, in fields, open spaces and sometimes rooftops. While more birds arrive vocalisations become more excited. Birds already present are aroused by the new arrivals and send up a chorus of contact calls.
As the sun sets a sudden silence will begin. Birds on the periphery of the gathering will now start to make silent flights to the middle of the flock. As they leapfrog their neighbours they trigger the next wave of birds to move towards the centre. Soon the flock will have formed into a dense mass.
After sitting silently for a while they then start to break for the roost trees, pouring into the airspace about the trees with lots of noise and excitement.
The chatter continues for a while in the roost then gradually subsides for the night. All crows are very intelligent birds with complex social lives, rooks are known to have over 40 different calls, almost amounting to a language.
There are several large roost gatherings in our local area. The island on Hogganfield Loch in the east end of Glasgow has perhaps 8,000 birds, many gathering in the fields and adjacent golf course before flying to roost. Another very large roost takes place in Balloch Castle Country Park.
In Milngavie there is a magpie roost of around 50 birds in trees close to the library.
The largest roost in Scotland is at Hatton Castle in the Ythan Estuary with 65,000 birds recorded.
If readers would like to witness a roost, I will be leading a guided walk for Urban Roots, a community led environmental organisation on the south side of Glasgow, on November 22, with no charge. Booking is necessary, phone 0141 6132766. The roost we will watch is at Mall’s Mire near Hampden and consists mostly of jackdaws with smaller numbers of crows and magpies. I’d recommend ‘Crow Country’ by Mark Cocker for more information about these birds.