My daughter, Chloe, has just finished a degree in environmental conservation at Bangor University. In her final year she did her dissertation on nightjars, and has written a guest blog about her findings. We have been out looking for nightjars this summer too and have had a chance to test some of Chloe’s ideas, so I have added a couple of paragraphs at the end.
—
Have you ever been walking at dawn or dusk and heard a really eerie churring noise? This may have been a nightjar (https://www.rspb.org.uk/birds-and-wildlife/wildlife-guides/bird-a-z/nightjar/). They are such interesting and genuinely weird birds, however they are relatively unknown. Trust me I know because I chose to study them for my dissertation and trying to explain what a nightjar is, is surprisingly difficult.
So what is a nightjar? They are crepuscular (coming out at dawn and dusk), ground-nesting, insectivorous and well camouflaged. They seem to fly effortlessly, like they are weightless, adding to their creepy nature. They also make two other distinct sounds a ‘gwep’ contact call and a wing clap. They are migratory, spending the summer on our heaths and the winter in sub-Saharan Africa. All of these frankly weird and unique things are what made me want to study nightjars and share my findings.
Last year (2019) I came up with the idea of trying to understand the link between people and nightjars. I wanted to know, to what extent human disturbance affected their distribution. I was limited on resources and time so chose three areas close to me but all with surprisingly different levels of disturbance. Buckler’s Forest (most disturbance), Wildmoor Heath (middle) and Hazeley Heath (least disturbed). The way of working out disturbance levels was not very scientific, as it was quickly discovered that quantifying disturbance was not an easy task. Fortunately, average footfall and accessibility for each site was known from communication with the rangers.
The study method involved walking a pre-determined route and marking on a map where each encountered nightjars was, providing a distance from the path.
Despite the simplicity of this study I still ended up with a large amount of data:
- My own records (from 3 visits to each site) of the distance of observed birds from the path and from the nearest roads
- A maximum / average number of birds encountered over all my visits
- Information about weather and degree of disturbance on each visit
- Time of encounters
- And some historical data – From Hazeley Heath there were locations of nightjars from past surveys (RSPB) and from Wildmoor and Hazeley there were population estimates over previous years starting at 2003.
So, what did I find? I learnt a bit about some of the challenges of doing a survey like this. One of the problems was that the original hypothesis was overly simple. As soon as the study started it was clear that nightjar territories, and potential breeding success, were being negatively impacted by human disturbance. So, I chose to focus on the distribution of male nightjar territories in relation to human disturbance.
I already knew that nightjars, because they nest and sometimes roost on the ground, are extremely sensitive to disturbance by walkers and their dogs, cyclists, and horse-riders. I discovered that paths and roads seem to create the boundaries of male nightjar territories, and trees and poles alongside these paths and roads are ideal song posts for male nightjars. So, one form of disturbance, the creation of these roads and paths, may be somewhat beneficial for nightjars. However, it was also that changes to manmade features determine whether nightjar territories change shape or whether they even work at all.
Over the last few decades conservationists have demonstrated that when appropriate new nightjar habitat is created, the breeding population increases. My project suggests that one of the three sites is unlikely to support a nesting population. Even though it is advertised as having nightjars, and there is a thriving source population close by, it may simply not be suitable nightjar habitat due to the level of disturbance and the constraints of the site. A second site appears to have potential for more nightjars within the existing habitat, but no real opportunity for expansion. The third site has the capacity for more habitat, and in the year since this study took place there has been large scale tree removal, creating more potential nightjar habitat.
My study also raised some interesting questions about the relationship between people and nightjars. Some of my findings suggested that nightjars are impacted by particular types of noise pollution, such as traffic and machinery. It seems possible that these types of noise, particularly when continuous, drown out the churring of the male nightjars and make it harder to find and keep a mate. With more research, there is potential to discover more about how nightjars react to human presence and the larger scale disturbances we cause.
The findings from this study could help conservationists and planners create better habitat for nightjars and the underlying techniques can help us get a greater understanding of how to establish the impact of human disturbances on different species especially migratory ones.
—
Since Chloe started work on this project she has been given at least one opportunity to extend it to another part of the UK. We have revisited several of the sites mentioned in the dissertation and have found that nightjar numbers are at a similar level to the study year. At Hazeley Heath we have seen and heard nightjars using an area that was created over the winter. We have also seen and heard nightjars in another nearby area that we ruled out of the original project as being unsuitable. While looking for nightjars we have seen woodcock, tawny owls, a hobby, a cuckoo, and lots of bats. We have also enjoyed some spectacular sunsets.
If you would like to enjoy this special avian experience in 2021 then look for nightjar walks organised by your local wildlife trust, council, or the RSPB. If you want to know more about nightjars and their preferred habitat then here’s a blog post that I wrote last year (SANGs and fern-owls)
(Thanks to Dave Braddock for the nightjar picture.)
It isn't easy being green 