Aug 19 2020

A Master of Camouflage

For many of us, the start of August marks the arrival of high summer, bringing long hot days and balmy nights and summer holidays! For most species of birds, it is a time of change. Both resident and migrant, the breeding season is all but over. Many will become very secretive, as missing flight feathers during their summer moult affect their ability to avoid predators, who are looking for food. Some species, such as cuckoo and swift, will be preparing for their southward journey back to their wintering grounds, while others will be resting and feeding themselves up in anticipation of making the same journey in a couple of months’…

A typical glimpse of a nightjar at sunset

With this change of pace, much of the birdsong that has filled the woods for the past few months fades away, and in the midday heat it can be almost silent, with the only sounds the chirping of grasshoppers and the buzzing of bees. Although these birds start their migration south in August, if you take a walk at sunset, there’s still a chance you might be able to hear one of our most elusive migrant species, the nightjar.

The lowland heath at Trendlebere Down is an important site for breeding nightjar, one of only a handful of sites on Dartmoor. As the sun sets over the heathland listen out for a monotonous “churring” call, often alternating between two slightly different frequencies. This can continue for several minutes at a time, before ending abruptly in a questioning “quoip?” or a loud wing slap, sounding like a single human clap.

perfectly camouflaged nightjars nest in the open on the ground

In contrast to its closest UK relative, the swift, which lives much of its life on the wing, the nightjar is much more land-based, nesting amongst gorse and heather on open ground. If you are lucky enough to spot one of the birds as it swoops across the twilight sky in pursuit of moths, the swept-back wings and agile flight will make the family resemblance to swift much clearer.

As with most nocturnal creatures, there is a wealth of folklore surrounding the nightjar, in particular the belief that they drank the milk from nanny goats, causing them to become dry or even go blind. This tale is immortalised in the Latin name of the bird, Caprimulgus, which literally means “goat sucker”.

Although still a scarce species in the UK, with less than 5,000 pairs believed to breed here, nightjar can also benefit the open spaces left behind by felling operations or scrub clearance on the open heath that provide excellent breeding habitat in the following season.

The open heath on Trendlebere Down – perfect habitat for the nightjar

Nightjar are late arrivals to the UK each year, with most birds returning from their wintering grounds in sub-Saharan Africa between mid-May and early June. Because of this, eggs are often not laid until late June or early July, just as the breeding season draws to a close for many species. The nest is usually tucked in amongst gorse or heather or woodland clearing and contains one to three eggs. The location of the nest site at ground level means it’s very vulnerable to disturbance, particularly by dogs and humans.

Nightjar have been described as the basking shark of the night with huge mouths ready to scoop up flying moths and beetles. They have large stout whiskers to help funnel the insects into their mouths and to protect the eyes from damage.  They even keep them clean and well-groomed using a specially adapted toe which resembles a comb.

A specially adapted comb, used to comb their whiskers!

This summer, bird ringers have been taking part in a survey to ring and collect mouth samples from nightjar for DNA analysis.  This is part of a national project, which aims to characterise current levels of genetic diversity in the fragmented UK population and to understand any implications the findings may present. On several evenings on Trendlebere Down, just when it is getting dimpsy, the ringers have set mist nets on the heathland. They have used a tape lure recording of the males churring song, along with wing clapping and the quipd quipd calls uttered mostly when in flight, to attract the birds into the nets. Unfortunately, the nightjars managed to outwit the ringing team at Trendlebere Down, but 6 were ringed at other heathland sites in South Devon which will add to the national picture.

A rare view of the gaping mouth of the nightjar – taken by the bird ringing team while carrying out one of their night-time surveys

By August, most nightjar will be heading away from their breeding areas, migrating to spend the non-breeding months in Africa and recent tracking of birds fitted with satellite devices has revealed new wintering areas in the Democratic Republic of Congo.

The nightjar is on the amber list of endangered species so it needs extra help from us. Please take care by sticking to paths and keeping your dog close to avoid disturbing it. Heathland habitats are very vulnerable to wildfires so please follow the Ranger Code and don’t have BBQs or open fires.

Watch this video of Andy Bailey from Dartmoor National Park as he goes in search of nightjar on Trendlebere Down https://www.facebook.com/enjoydartmoor1/videos/2690635674525857/

You can find more Dartmoor National Park videos on their YouTube channel at https://bit.ly/3aiT4ru

Written by Tom Williams
with additional words and photos from Nik Ward

For more information please visit https://eastdartmoorwoods.org/

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