Starling murmurations are one of the most mesmerising spectacles of nature. Every year hundreds of thousands of starlings congregate around Gretna in the Scottish Borders where they perform a nightly display of synchronised acrobatics, shapeshifting into a variety of often recognisable forms and patterns for up to half an hour before suddenly dropping down to roost in the trees below. As winter draws close the starlings migrate from Scandinavia to the UK where it is milder. In the mornings the starlings disperse from their roost to find food. Each evening the starlings return to their pre-roost assembly point, some travelling up to 20 miles. There follows a display of swooping, diving and swirling as the bird join en-masse and fly in a variety of patterns and shapes. Gradually the birds knit more closely together until the sky resembles a dense cloud of black ink pouring over the skyline. It is believed that a number of factors contribute to this avian behaviour. Firstly, there is safety in numbers. Birds are most vulnerable when asleep so to roost in a large gathering allows the birds to look out for one another. The drop in temperature may cause the birds to huddle together en masse whilst flying at high speed in order to boost their body temperature prior to roosting. As to the reason for the dramatic patterns that form their aerobatic displays, it is interesting to note that shapes of sea creatures such as dolphins, whales and squid are commonly recognisable to onlookers. Large concentrations of fish in the sea are known as 'bait-balls'. When fish are threatened by a predator they tend display similar behaviour to the starlings by swimming in patterns and shapes, with each bird trying to get to the centre of the group. These shapes may deter predators. Starlings are at risk from birds of prey and it is it thought that the dramatic swirls notable in their displays are created as each bird turns away from potential danger.
