Oystercatchers sleep with one eye open to look out for dogs and humans

Oystercatchers sleep with one eye open while roosting on the ground so they can keep a look out for dogs and humans, study says

  • Birds use ‘peeking’ to sleep, meaning they keep opening one eye to spot danger
  • Near-threatened species did this ‘significantly more’ when humans were near
  • Scientists said that dogs represented a ‘real and unpredictable’ threat to birds 

Oystercatchers sleep with one eye open to look out for humans and their dogs, which represent a ‘real and unpredictable’ threat, a study has revealed.

When the near-threatened species roosts on the ground at high tide it uses ‘peeking’ to keep safe, meaning the bird keeps half its brain active and opens one eye about 12 times a minute to check for danger.

But scientists watching the birds in North Wales found they kept their eye open for ‘significantly longer’ periods when humans were within 490 feet, and ‘particularly’ if they had a dog with them.

The birds also peeked more times a minute in response to noisy boats, but for shorter periods suggesting they had learnt the sound did not represent a threat.

Oystercatchers peeked ‘significantly more’ while humans and dogs passed nearby, said scientists. They watched 300 birds in two sites in North Wales

The scientists said dogs represented a ‘real and unpredictable’ threat to the birds, which like to roost on the ground at high tide

It is thought that lockdown, and the reduced human activity, has offered many birds that use ‘peeking’ – including oystercatchers – a welcome respite. 

In the study, scientists filmed the eye movements of 300 sleeping birds using a spotting scope fitted to a camera for three minutes over a period of four months.

They recorded how the ‘peeking’ was affected by human activity, weather, and the surrounding birds.

Monitoring took place at two sites in the Menai Straits where the species is known to roost in large numbers over the winter months.

‘It seems that dogs were a real and unpredictable threat that the birds needed to actively monitor,’ said Zoology lecturer at Bangor University Graeme Shannon.

‘We also found that birds alter their vigilance depending on the size and behaviour of their (flock). If there were more birds around them, they peeked less often. 

‘Safety in numbers – with more eyes watching for danger – clearly means more rest.’

Oystercatchers have been in decline in the UK, dropping 35 per cent over the last 25 years

Dining on cockles and living on coastlines: Oystercatcher facts 

The oystercatcher, or Haematopus ostralegus, is considered a species of concern in the UK.

The large, stocky birds are identified by their black feathers, orange-red bills and reddish-pink legs. 

They are found across all coastlines in the UK and Ireland, according to the RSPB, and grow up to 17 inches in length.

The species is often seen fishing in the surf for cockles, its main food source.

There are an estimated 110,000 breeding pairs in the UK, and 340,000 birds that overwinter in the country every year. 

Warmer and windier conditions were also shown to cause the birds to peek more often to check for potential predators.

The scientists argued that the coronavirus lockdown has helped many animals, with reduced disturbance allowing them to get more sleep.

Those facing regularly disturbed sleep get less rest and use up more energy, possibly harming their chances of survival in the long-term and particularly during winter when food is scare.

Oystercatcher populations have dropped 35 per cent over the past 25 years, according to the British Trust of Ornithology.

Noise and human activity in coastal habitats are thought to be key threats.

The birds are also thought to have taken advantage of lockdown to nest in new sites.

Two pairs have nested in Stanpit Marsh, Dorset, for the first time in more than 50 years.

Their decision is thought to have been encouraged by the absence of boats, which would normally disturb the pair.

Another pair has settled in at man-made Bodenham Lake, Herefordshire, for the first time ever.

The site was a gravel pit before it was converted by the Herefordshire Wildlife Trust and New Lead Sustainable Development. 

The study was published in the Journal of Zoology. 

Source: Read Full Article