Nightjar

Regular readers of this column may have seen my piece earlier in the week which mentioned our efforts to catch Nightjars in Thetford Forest. This work, which involves fitting tiny radio-transmitters to some of the birds we catch, is being carried out to support a PhD student who is looking at Nightjar movements and breeding ecology. Small teams of trained and licensed bird ringers are out several times a week at the moment (depending upon the weather) and we have been fortunate in being able to target and capture a small number of birds within our defined study areas. Our success rate has been such that there have been very few nights when we have failed to catch a bird.

I have been particularly fortunate to have seen a number of birds in the hand and to have caught a breeding female in one of my nets. This particular bird was tracked a few days later, through her radio transmitter, to a nest site just a few hundred metres from where I had caught her. She was found to be incubating two eggs (Nightjars typically lay from one to three eggs) and we will be able to follow her progress as the season continues. She might go on to make a second breeding attempt before departing south towards her African wintering grounds. Nightjar nests are placed on the ground, within an area that is bare or sparsely vegetated, and the female relies on her cryptic colouration (a mottle of greys and browns) to remain hidden from potential predators.

The Nightjar is found across much of lowland Britain but only where suitable breeding and feeding habitats exist, so it tends to be localised within this wider range. Thetford Forest is something of a stronghold for the species, with the birds making use of areas of clearfell within the larger blocks of coniferous woodland. The reliance on areas of clearfell and young plantation woodland means that the size of the breeding population within Thetford Forest is very much dependent upon the area of suitable habitat available. As the newly established plantations mature they become increasingly unsuitable for the Nightjars. Fortunately, the Forestry Commission now manages the Forest with this in mind, maintaining a good area of sufficiently young blocks to provide enough breeding habitat for the Nightjars and other early successional birds like Woodlark. Work already carried out within Thetford Forest suggests that the Nightjars forage for food within a kilometre or so of the nest, so suitable nesting and feeding habitats need to be located close together. The mosaic of forest blocks provides the mix of habitats required by the Nightjars and, with careful management, their future within the forest looks secure.

Transition

It is still light when we arrive, the brightness of a summer’s day slowly slipping into the softer tones of evening. We are in the forest to catch and radio-tag Nightjars for a PhD student studying their ecology. Having chosen suitable spots, we quickly set our fine mesh nets and retire to a nearby forest ride to await the arrival of night and the stirring of the Nightjars. There is time now for patient watching and hushed conversation.

The background drone of flies dissipates and the final bird song slips towards silence, a solitary Song Thrush a last bastion of the daytime brigade. The time for the ‘night watch’ approaches and the first of the evening’s bats appears; a Noctule, an early riser that can sometimes be seen feeding alongside swifts, hawking the air for flying insects. The bat makes several passes up and down the ride and I curse myself for having left the bat detector at home; it would have been good to ‘listen’ to the Noctule as well as watch it pass.

The colour begins to leach out of the vegetation as the daylight fades to replace greens and browns with silvers and greys. A short squeaking note, much like a child’s toy, catches our attention and we glance up to see the dumpy form of a Woodcock silhouetted overhead. The forest seems to support fair numbers of these rather unusual waders – a woodland bird that probes damp soil for earthworms and other invertebrates. Then we hear it, a soft mechanical churring call – a Nightjar, distant but welcome. Soon it is joined by other birds, two close by and in the area of our nets – this bodes well. The closest of the birds is in flight, the churring interspersed with wing claps and calls, moving around off to our right. Then, it is caught, silhouetted against the sky, its effortless buoyant flight taking it in an arc around us and up into the top of a nearby oak. The bird can be seen perched on its song-post, advertising its presence to other birds.

These first excursions provide breathtaking views and we can stand and enjoy them, knowing that it will be another hour before we can turn on the tape lures that should attract the birds into our nets. Being nocturnal, the Nightjar has excellent visual acuity and would be able to avoid the nets if we tried to operate them in this half-light. A sheet of cloud has formed and by 10.30 it is dark enough to try our luck. Each of us manning a single net, tape lure running, we crouch nearby watching and listening, hopeful that we might catch one of these truly amazing birds.