“Can you commit three days a week, 9-5?” They said, “Yes, sure I can,” I replied. And so, I have; diligently spending the past six months head down, bottom up in hay meadows, wading through reedbeds hunting for water voles and bashing my way through neck high scrub.

What they didn’t mention that day in the interview, was quite how much I would be entering the world of the crepuscular, the hours of dawn and dusk. From winter commutes, late night parties and early morning baby feeds I have done my share of crepuscular living, but not, until now, undertaking slow walks in nature hunting for some of our most intriguing wildlife. 

In his book ‘The Seabird’s Cry’ Adam Nicolson discusses the concept of ‘umvelt’, coined by the biologist Jakob von UexkÜll.  ‘Umvelt’ describes the unique way each organism perceives and understands the world around it. It highlights that each species lives in its own unique sensory world to which we, as humans, may be partially or totally blind. Seeing wildlife thrive in the dark on my crepuscular adventures has been a brilliant way to appreciate this concept of ‘umvelt’.  

Nightjars

 A late evening drive to Padworth Common sees us arrive at sundown. We walk to the far side of the common and there watch and wait, listening intently for the characteristic sounds of the nightjar and the shadowy silhouette of its flight.

Migrating to the UK in late spring they take up residence on heathland and cleared woodland to breed. Foraging mostly for moths they are observable at dawn and dusk flying over the heathland, weaving round stands of trees. They do not echolocate, instead relying on their large eyes and the reflective layers in them for excellent night vision.

They communicate loudly in the dim light and it is not long before we are cupping our hands behind both ears listening to the iconic ‘churring’ noise male nightjars perform when perched in a tree. As the churring continues we determine the direction of the sound and mark it on the map.

Suddenly, from our right, swoops in the shadowy silhouette of a nightjar with its pointed wings gliding much more gracefully than I had anticipated. It swoops past and disappears against the backdrop of the trees in the darkening sky. We mark it on the map.

The churring stops and we wait as the sky darkens. Then suddenly another nightjar appears, this time, flashing its white wing markings identifying it as a male displaying to others in the area. It flies within metres of where we stand before disappearing, again, into the dim night.

Just as darkness fully settles and we start to consider returning home the unmistakable sound of ‘wing clapping’ is heard from over the common. This distinctive sound made by the males to attract a mate is generated by the force of clapping their wings together in flight. 

As I stand in the darkness contemplating what I have witnessed I am struck by how very differently they experience the world to us; whilst we as humans hurry away from the dim light of evening to the safety of indoor living they emerge to exploit the niche it offers.

They clearly thrive in this dimly lit world, taking advantage of the moths available and communicating with bold distinctive sounds and strong flashes of white that stand out boldly in the dark.

In terms of ‘umvelt’ there is little we as humans share with nightjars, clear to me as I endeavour not to crash into a tree as we walk back to the cars whilst the nightjars weave and swoop their way successfully overhead. But, to have had the privilege to stand in the darkening night and witness how brilliantly adapted they are to their crepuscular living and get a hint of how they might experience the world leaves me both calm and amazed. 

Glow worms

Whilst the nightjars’ night vision is seriously impressive the ability of glow worms to generate their own light is simply mind-blowing. Like most animals I unknowingly emit non-visible, infra-red radiation but am totally unable to generate radiation in the visible light spectrum. Not so for these amazing creatures found in some of our BBOWT nature reserves.

As I drive to my very first glow worm survey I watch as the sun sets and lights turn on in people’s homes. I arrive in the car park to meet the other surveyors in the dim evening light. We separate into groups and take on set sections of the reserve walking the transects.

At first, I am really not sure what I am looking for; how bright are they? how big are they? how easy are they to see? Every white flower in the long grass along the woodland ride makes me take a second look but then, suddenly, it all becomes clear.

A fellow surveyor shouts, ‘there’s one’ and I look over. There, among the long grass, is an intensely bright spot of light, like a greenish LED light bulb. I stare, incredulous. In one moment, every story and myth of magical woodland creatures makes perfect sense, and I am transported into a world of fairies.

On closer inspection I find a dark coloured grub clinging onto a grass stalk with the last few segments at its rear glowing bright green/yellow. This is a female glow worm, steadily making its way up the tall grass to position itself as well as possible for a male to spot it and come to mate.

Glow worms are beetles, but the females are flightless and look much like larvae. Quite unremarkable until they exhibit their amazing ability to bioluminesce. I suppose I did my fair share of showing off to attract a male but I’m fairly certain I would always have drawn the line at climbing up a pole with my bottom glowing.

Yet, peculiar as it sounds to us as humans, when given some thought it is clearly an excellent way of attracting a mate in the dim light of evening and on into the darkness of night. Without these little beacons of light guiding the male it would be like finding a needle in a haystack for them.

As we continue to walk our transect more lights are spotted, some low down just starting their climb up the grass, others already high up the stems glowing away. This behaviour of female glow worms makes them relatively easy to count and survey the populations. The males, however, look like brown beetles and fly about hunting for females and are much more difficult to find.

A ‘lure’ board with green LED lights mounted on it is left out as part of the survey to attract males but none are ‘fooled’ this time and it remains empty. After counting a number of lone females we do find one with a male in attendance so is added to the survey count. It is 11pm by the time we all return to the car park and pool our counts to determine the total number found.

As we stand together there is a sense of not wanting to leave, perhaps it is the enjoyment of socialising with others or simply the novelty of being out in the dark that makes us linger. Or perhaps it is the little bit of magic that those little lights in the grass have breathed into the night that makes us want to stay. Whatever it is, we eventually depart, because we as humans are not suited to their world, in our ‘umvelt’ the comforts of home and electric light are reassuring when darkness falls and so, to home we return, leaving the glow-worms to their ‘umvelt’ and the dark of night.

So, two amazing nighttime adventures and two amazing species encountered. Both very different to each other, and both very different from me.  All of us existing in the same world, in the same environment, yet all experiencing it and perceiving it differently, adapted in our own ways to survive in the world as we perceive it, in our own ‘umvelt’.

Of all the lessons I am learning on this traineeship the appreciation and respect for species and their ‘umvelt’ is proving amazing and invaluable and will, I hope, guide me in my future.

Vicky Hall, Ecology Trainee, September 2024