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.