Land management for nightjars
The nightjar is now a scarce breeding bird of lowland heathland, forest clearings and clearfells throughout Britain, north to southern Scotland, and in coppice woodland in south-east England.
Nightjars were once much more numerous and widespread than today, but now appear to be recovering.
Extensive clear-fell harvesting in mature commercial forests planted after the Second World War has produced large areas of new habitat and, simultaneously, conservation initiatives have restored much of the lowland heathland. Nevertheless, large parts of the former range remain unoccupied and the nightjar is still at risk from habitat change.
What do nightjars need?
Nightjars are summer visitors to the UK, arriving in mid-May. They usually raise two broods of one to two chicks in secluded patches of bare ground within low, often shrubby, vegetation, before migrating south in September or October.
Foraging is mainly at dusk and dawn, and through the night when they need to, on moths and other large flying insects, which they catch mainly on the wing. Although they feed over heathland and along forest rides and edges, nightjars are most successful when there is a range of food-rich habitats at hand. These include wetlands – such as reedbeds, fens and grazing marsh – native woodlands, mature hedges and old pasture.
On lowland heathland, nests are usually located in small, naturally occurring gaps in deep heather in dry heath, with a scatter of plant debris, but not live grasses. This offers shelter, camouflage and seclusion from potential predators. Scattered trees are used to sing from and to roost in.
In conifer forest clearings, clear-fells and restocks, especially on former heathland, the vegetation structure is like that of heathland, augmented with lying brash, which provides added concealment. Restocked clearings are abandoned as the tree canopy closes over the open ground around seven to eight years after planting, although these may be used if the crop is slow growing, for up to 12 years.
In coppice woods, nightjars nest in large recently cut coups (clearings) and continue to occupy them until the canopy covers much of the ground, in, for example, four to five years, depending on the rate of regrowth of the coppice.
Lack of disturbance
There is increasing evidence to suggest that nightjars are vulnerable to disturbance, for example by dogs, which flush the adult from the nest allowing predators to take the eggs or chicks. Significantly, fewer chicks are raised to adulthood on sites with high levels of disturbance than on undisturbed sites.
How can I encourage nightjars?
- Ensure that a good proportion of old mature heather is retained with naturally occurring small gaps, in areas that are free from disturbance. How much old heather is left will vary by site, but 10–20 per cent of the heather at this age, and distributed around the site, should provide sufficient opportunities for nesting.
- Where the heather is uniform and lacks gaps, uprooting two or three plants together can create one to two metre-square gaps. Cutting will have limited value, as the plants will regrow relatively quickly. It is useful to create a number of such gaps in each area to provide a range of options for the nightjars to choose from – 100 per 0.01 sq km is equivalent to just 0.02 per cent.
- Keep a sparse scatter of trees as song or lookout posts – this will vary according to the character of the heath, but 10 trees per 0.01 sq km is acceptable.
- Where mature or old heather is absent or scarce, dense bracken may provide alternative nest sites early in the breeding season, but these are often lost as the bracken grows. It is important to prevent the bracken spreading.
- Avoid mechanised bracken control wherever nightjars might be nesting.
- Manage access, where possible, by providing defined paths that lead visitors away from nightjar nesting areas and by encouraging dog owners to keep their dogs on leads during the breeding season.
In forestry clearings
- Avoid mechanised management operations on clear-fells between May and September, when they may destroy nests.
- Following clear-felling, avoid rolling lop-and-top/brash – it provides shelter for nest sites.
- Ensure that there is a continuity of clear-fells greater than 0.02 sq km in size. Where possible, create a waved or scalloped edge to the coup – this increases the length of foliage edge for feeding along.
- Wherever possible, delay restocking to prolong the openness of the clearing.
- As the new crop grows up, carry out inter-row cultivation, for example in every second year, to prevent rank vegetation from developing.
- Manage access, where possible, by providing defined paths that lead visitors away from nightjar nesting areas and by encouraging dog owners to keep their dogs on a lead during the breeding season.
- Less rigorous beating-up allows gaps to develop in mature forest stands.
In coppice woodland
- Avoid mechanised management operations on coppice coups between May and September when they may destroy nests.
- Ensure that there is a continuity of recently cut coups each in excess of 0.02 sq km in size.
- Ensure that most of the lop-and-top is removed – a light scatter can provide shelter for nest sites.
- Where possible, create a waved/scalloped edge to the coup – this increases the length of foliage edge for feeding along.