Some things in life are even more important than nightjars. Once again, events conspired against the project this year with the result that as far as fieldwork was concerned, the team was reduced to just one person (BL) for large parts of the season.
Regardless of the team size, the plan for this year had always been slightly different. We would as usual deploy AudioMoth devices at viable territories to undertake the most thorough count we could. However, with regard to in-person observation, the plan was to concentrate far more on a single location (site BA) than usual, with the intention of building a clear picture of how many birds were present and what was happening in the breeding cycle.
Despite that, I (BL) always like to see my first Nightjar of the year at my most local site (AF). By 7th May I’d neither seen or heard one so decided to try the main study site (BA) instead, at which the first male of the year was recorded. A number of subsequent visits to AF (and its associated local sites) revealed that the birds probably find these sites too overgrown and none were recorded there all season. There is potential new habitat very nearby, so we anticipate that we may yet be finding birds here again, but this was the first year since 2003 that no Nightjar were seen here.
Site BA remained quiet with just one active male until the evening of 22nd May when BL and HM visited. The bare statistics of 3 males feels underwhelming compared with the experience of the evening, when it felt like we were being approached from all directions constantly by many more birds, the flash of white wing spots vivid in the twilight as the males interacted – a memorable highlight of the season.
We’re consistently conservative with our recording, logging only what we can guarantee were individual birds, whether that be through simultaneous visual observation or distinguishing through audio, either in the field or retrospectively. That evening was a one-off event, the birds
dispersing to leave two males holding overlapping territories and eventually two females joined them. During this early part of the season, one of these males sang for 9 minutes solidly. Not quite the 18 minutes uninterrupted that we recorded at site AO, in 2021, but still a good indication of the kind of effort that males will put in early in the season, when there is some potential competition.
‘BA’ is the site at which BL has found the most nests. It’s also well positioned geographically to help answer some of our questions surrounding foraging behaviour, particularly on less favourable evenings within their own territory. Those questions could be answered, potentially, with the help of a GPS tag. In previous years we’ve used radio tags which periodically transmit a radio pulse, in order that we can detect it in the field with a handheld antennae and receiver. In contrast, a GPS tag logs accurate location information and stores it onboard. [having discussed this with Brian Cresswell at Lotek,] our plan was to bind the two tag types together to form a ‘hybrid’ tag that both transmits radio and receives GPS data. This would then be attached to the bird’s central tail feather with a soluble string that would dissolve easily on contact with rain, causing everything to drop off the bird, at which point the radio tag’s pulse would facilitate us finding the pair of tags somewhere (theoretically!) on the forest floor.
The plan was that BL would, as usual, find a nest at site BA, and that the male of this pair would be selected to study, with the opportunity to also ring the female and chicks. The first flaw in this plan lay in misplaced confidence that another nest would be located at this site, and the second, the plan’s reliance on that; in previous years we would, simultaneous with nest searching, attempt to catch birds early in the season, giving us more than one opportunity to tag.
The last two years have seen the same male return and breeding has occurred in roughly similar areas, making that an ideal starting point. The previous two nest sites were relatively undisturbed, but extensive Wild Boar diggings nearby suggested things might be different this year. During the first search of the area, a group of 10+ Wild Boar were disturbed from their sleep among the gorse, and other large mammals were constantly present too. The Wild Boar diggings occurred sporadically across the site throughout the season – common throughout the Forest of Dean, but much less so at this particular site. In more promising developments, huge areas of the site that were previously not really suitable for Nightjars nesting now looked ideal, and yet further areas now suitable through new clearfelling. Thorough searches for nests would reveal both of the roosting males almost every time in a whole variety of locations but only once this season was a female found in the daytime, sat atop of pile of wood chippings in the shade on one of the hottest days of the year, with neither eggs or chicks. Apart from that, where the females had been spending their days, and whether they’d succeeded in breeding, remained, as so often with these birds, a complete mystery.
On 26th July we put up the net for the first time of the season, still at site BA, and caught a female. We ringed her but she wasn’t suitable for tagging. She was in the process of de-feathering, seemingly in preparation for a first breeding attempt of the year, even at this late stage. This explained why a nest hadn’t been found for this pair at least. Perhaps the other pair were also yet to breed or perhaps they’d silently got on with it, avoiding our attention.
Although largely concentrating on site BA and despite the other sites being monitored by the AudioMoths, we still made time to visit other sites, if not as extensively as previous years. Sites K and N in the west were pleasant surprises, collectively holding a minimum of 3 males. These birds nicely made up for the numbers lost at site AF and others.
Site AX in the north-east of the forest has always been a favourite site to watch, though in more recent years seems to have been less active. This year, early AudioMoth recordings strongly suggested a breeding pair but a thorough search yielded nothing at all although during one much later visit a female did arrive, causing the male much excitement and some very memorable close-up views of them both. Later visits would show that she had seemingly left again. He would be our third and final (failed) attempt to catch a Nightjar this year, in early August.
Now that the AudioMoth recorders have all been gathered in, we can tally Nightjar at 15 of 19 prospective sites. Of these, 3 were new sites, to us. On 22nd May at 2130, 7 males were recorded churring simultaneously at 7 separate sites.
In total we were aware of Nightjar being seen or heard, at least once, at 18 sites. At least another 7 potential sites were not surveyed. Although (at the time of writing) we are unaware of anything to confirm successful breeding, the number of sites occupied remains consistent with the last few seasons.
The process of analysis, for presence or absence of male Nightjar, of the AudioMoth recordings, has been transformed by the availability of an application that automates this. We were very fortunate to be contacted by Chris Scott, who builds recognition software, offering to make a Nightjar tool for us! Knowing that we had this available to us enabled us to configure the devices to record at dusk and dawn, without adding substantially to the time required for analysis. Nightjar are known to sing more in the pre-dawn period. The Forest of Dean, although visually beautiful, suffers a fair bit from traffic noise, both road and air, and the pre-dawn recordings are often less spoilt by anthropocentric sound. Whilst partly an aesthetic consideration, this does have a practical aspect in producing clearer sonograms for analysis.