Understand starling roosts

New research shows how huge winter starling flocks coordinate their massed aerobatics.

Starlings, RSPB Strumpshaw Fen

Shape-shifting congregations of thousands of starlings at dusk, called murmurations, have an almost volcanic energy.

“Carousels of birds chimed and merged, like iron filings made to bend to a magnet,” writes birder Tim Dee in his book The Running Sky. But explaining how starlings gather in such numbers and mostly avoid midair collisions (fatalities are known in some flocking species) has long provoked much debate.

Now a multi-disciplinary study by the University of Warwick has found that flock density is key. “A bird is safer from predation if it joins a big, dense flock,” says researcher Dan Pearce. “So in theory large flocks would eventually be totally opaque. But we discovered that birds select the optimum density so they never quite get that packed. If you look at photos of flocks, there will always be gaps where you can see the sky.

“Each starling constantly monitors the trajectories of about six or seven of its nearest neighbours, while also making adjustments so that it can still see light areas – that is, patches of sky. It must always be able to gather vital information about its surroundings.” Amazingly, this process is entirely instinctive. “The birds do it almost without thinking,” says Dan.

Where to see a starling roost

Starling roosts vary in size and shift location from year to year, with the largest numbers gathering in cold weather from December to February. Clear, calm, starry evenings are best – arrive at the location about an hour before dusk. 

Click here to discover 13 best places to see a starling roost in the UK. 

Help survey starling roosts

The Society of Biology and University of Gloucestershire are organising a national starling murmuration survey this winter. To join in, you need to estimate the size and duration of flocks, and record the time, weather, air temperature and if any birds of prey were in the vicinity.

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