2019 Nightjar season summary

The 2019 Nightjar season officially started for me on the 10th May. I’d already visited 4 different sites on the preceding nights hoping for just a flight call or a moment of churring to let me know that they’d returned, but it was at a 5th site on the 10th that I heard my first bird of the year. In all likelihood, this would be a bird known to us, as we’d ringed birds at this site in previous years and they are pretty site-faithful. It churred briefly from the far side of the site, silently and invisibly passed me to the upper end of the site before making itself heard again, and that was it. Any other night of the season it would have been a disappointment, but as it was the first bird of the year it was enough for me to know that the following few months, just like the previous years, would be dominated by Nightjars. The project I’m involved with has been running for around 16 years or so, and is concerned with bio-acoustic research. It is necessary for a small number of birds to be caught each year, whereupon they are ringed and radio-tagged, in order to validate much of our data. This was our fourth year of using radio transmitters.

Female nightjar

A few visits to further traditionally occupied sites on subsequent evenings were quiet, and it wasn’t until the 13th that I’d find the next bird, at site 4. This too was assumed to be one of our known birds, and on the 16th we unsuccessfully attempted to catch it, thwarted by strong winds.

The Forest of Dean. All our surveyed sites are within this area.

The birds kept on arriving. By the 21st May, I was up to 6 males, with birds at sites 5, 4, 9, 10, 5 and 15. One of these birds (site 15) was confirmed using a technique that we’ve been piloting for the first time this year. We’ve been deploying AudioMoth devices at potential new Nightjar sites, as well as traditional sites that are past their best, with a view to letting the technology do some of the work involved in coming up with an accurate census of the forest’s nightjars. The AudioMoths were programmed to begin recording around dusk and to keep recording for a couple of hours. They were deployed to the sites in the daytime and left in situ for at least a few days each time. Not only would they hopefully alert us to the presence of Nightjars, but if the recordings were of sufficient quality, we’d also be able to determine their identity from previously obtained field recordings, or at least to distinguish them from one another, thus avoiding the possibility of double counting. Site 15 was actually a site where we fully expected there to be at least one male, but it was a good test for the very first deployment, and the device did indeed record the bird. This year we had four devices to make use of, and we tried to keep them out in the field for the maximum time possible, bringing them back to my PC in between to retrieve their data.

AudioMoth device

By the 28th May, I had another four birds, adding sites 11 and 2 to the list of occupied habitats. Other sites which I expected to be occupied by now seemingly weren’t, but I was confident they soon would be. On the 27th we made our first successful catch of the year, with two first-year males. Neither were ringed, which told us that they were not from any nest we’d found in previous years. These birds were unimaginatively named ‘Bird 001’ and ‘Bird 005’, after the channels on the radio receiver assigned to the transmitters that we fitted to the birds.

By the final day of the month, another five birds were located, spread across sites 1, 12 and 7, making a total of 15 male Nightjars. At this point, sonograms and analysis had not taken place, so it’s impossible to rule out double-counting at this stage.

Nightjar habitat in the Forest of Dean

I spent the first week of June revisiting some of the sites that I’d already established to hold birds (sites 7, 9 and 1), rather than continue to find new birds. I wanted to see which birds were showing any signs of being paired. However, by the end of the week, I couldn’t even confidently claim to have seen a female at all. They always arrive a bit later than the males, but this year they seemed particularly late.

The following week another bird was located at site 8 and a second male had put in a (temporary) appearance at site 4. Site 8 is a site that only ever holds one male. It’s hardly what you’d call prime Nightjar habitat, but it’s reliable, albeit a site that the male often fails to find a mate at. Despite this, it remains one of my favorite Nightjar sites. It’s in a valley which greatly reduces unwanted noise, and has a rather special atmosphere to it at this time of year. Glow-worms are regularly to be seen bio-luminescing while the never too far away Wild Boar frequently put in an appearance, with the ever-present (at all sites) additional soundtrack of roding Woodcocks, Tawny Owls, barking Muntjacs, etc. We caught this male and fitted radio tag 004 to him. The current total of male birds now stood at 17. On the 14th a further male was caught and radio-tagged at site 7 (bird 003). This was a bird we’d previously ringed and tagged back in 2016. n.b. that the radio transmitters are attached to the tail feathers and drop off the bird during their annual moult.

Radio transmitter fitted to male Nightjar

A number of new birds were identified the following week. Sites 6, 10, 14, and 13 all held new males, at least a couple of which seemed to be paired. On the 15th of June at site 2, we caught two female birds. Both were ringed and one (bird 002) was fitted with a radio transmitter.

On the 23rd June, I found my first Nightjar nest of the year, at site 2. Although it’s easily one of the hardest sites to negotiate due to the thick bramble, gorse and bracken on very uneven terrain, for whatever reason it tends to be the site I favour searching for their nests and have had the most success in finding them. It’s also another of my favourite sites to just enjoy watching the Nightjars. I found a nest on the same site the previous year too. This time it had just a single egg, so the second and final egg would be imminent. I let the female lead me away from the nest and noted the position and the date on which the chicks were due to hatch.

Nest site at site 2

The final evenings of June were largely spent at site 17. Site 17 has fast become yet another favorite of mine this year, having been largely overlooked in previous years, and although I felt the pair of birds had given me enough clues about the location of their nest, they managed to outsmart me somehow, and to this day I don’t really have any idea where they ended up going. Finding Nightjar nests in the Forest of Dean, in my experience, is never easy! By the end of June, the total count of male birds stood at 22. On the 25th June, along with a friend, I found the second nest of the year, at site 1. This nest, like the first at site 2, consisted of just 1 egg. I returned to this nest around ten days later to install a trail-camera.

The female on the nest at site 1

In the first week of July, another two birds at another two sites were added to the list (sites 19 and 20). I also returned to the first nest of the year at site 2, with the intention of installing a trail-camera at that site too. Sadly, between my first visit and my second, a large amount of birch debris had appeared on the forest floor, and it was apparent that clearance work had been undertaken in this re-stocked clearfell area. It was upsetting, but not surprising, to find that the Nightjars nest had been trampled, and all that remained were crushed eggshells. The Forestry Commission is very supportive of our work with the Nightjars, providing us with funds to cover some of our costs, keys to the forest and permission to drive the forest tracks at night. Mistakes happen, and most importantly, the F.C are keen to use our data to mitigate the chances of this occurring in the future, if indeed it was the clearance work that was responsible.

Nest at site 1

Much of the time between all of the above was spent tracking down radio-tagged birds, making audio recordings, looking for nests, putting out and retrieving AudioMoths, analysing their recordings, etc. One thing that really became apparent this year was the extent of movement around the forest that some of our birds were making. Bird 005 was the first to disappear from his site (2). He was a young male and was quite likely moved on by an older known male who arrived later. Bird 004 was the next to disappear from his site (8). He appeared to have had no luck in attracting a mate and perhaps had decided to try to find a new territory elsewhere. Then, following the failure of her nest at site 2, bird 002 also disappeared. If she was going to have another breeding attempt this year, it seemed that she would do it at another site altogether.

Scanning for bird 003 at site 7

Following a particularly good observation by a friend, I learned that one of our tagged birds may have been seen at site 11. This is a site at which we have spent little time in previous years. The AudioMoth that was placed here earlier in the season had proven that there was at least 1 male present at this site. After a late night of searching for new birds around the forest, I decided to drop in on site 11 with the antenna and confirmed that one of our missing males, bird 004 originally from site 8, had indeed turned up at site 11. He also appeared to have found himself a partner at last! The following night, not only was bird 004 still present, but incredibly female 002 and even the long-lost male 005 had also now appeared in the vicinity. Bird 005 spent at least the following days constantly on the move, and we never did manage to tie him down to any particular territory.

A female at site 5, a bird known from previous years

A return to the nest at site 1 made for another big disappointment. By the time I visited, the eggs should have hatched and the chicks should have been 1-2 days old. It was very quickly apparent that the nest was empty. All that remained was half of one of the egg-shells. The nest was actually well positioned, with only one likely direction from which to enter for ground predators, and even that entrance was protected by a layer of gorse. In order to see the nest, it was necessary to get within just a few feet of it. The ‘impenetrable’ side of the nest now had a clear parting in the dense foliage that had been created by a large mammal, which led straight to the nest itself. There’s a limited number of mammals in the Forest of Dean that would have been capable of pushing through that vegetation, but it will never be known what the culprit was because unfortunately, the memory card in the camera had filled up a few days prior to me making that next visit to the nest.

Back at site 2, bird 001 was still present and seemingly getting on with the business of breeding, along with the older male (the one that appeared to have usurped bird 005). Then bird 003 (a breeding male whose territory is site 7) also appeared at site 2. Sites 2 and 7 are around 6km apart from each other. Learning about these movements actually ends up posing more questions than answers. Why was he moving so far from his mate and nest at this stage? He was keeping a fairly low profile there, and if it hadn’t been for the fact that I heard a very brief churring while having eyes on two males (001 and the older untagged bird), I would never have guessed that there was a third male present, and wouldn’t have had cause to scan the area with the radio receiver.

At the time of writing, it’s now getting on to the end of August. Five nests have been found, 20+ sites have been identified to hold Nightjars, and perhaps 25-30 male birds accounted for, many of which we know to also be paired. Until full analysis of the sound recordings has taken place, we don’t know the exact number. Many birds have already left, their journey back to Africa underway. Others remain, late nesters who are now reaching the final couple of days at the nest, but it won’t be long until all the birds have left again for another year.

Just like every year that has gone before it, 2019 was a year that continued to raise more questions about this species. I’m looking forward to the 2020 season already, and we’re already making plans!