Have you ever dreamed of witnessing a silent, ghostly form flitting through the daylight hours? Or perhaps a mesmerising display of otherworldly lights flickering in the night? Believe it or not, you can experience both these enchanting phenomena at RSPB Ham Wall!
June is an excellent month to spot the ghostly Barn Owl hunting on silent wing during the day and Glow Worms creating tiny flickering lights among the vegetation as twilight descends and the reserve is draped in darkness. Keep reading to discover the best spots to witness these magical spectacles and learn some fascinating facts about these remarkable creatures!
Typically a night time phantom of the countryside, spooking and delighting people with its ghostly appearance as it glides silently past and its hoarse shrieking voice, in June with hungry chicks to feed Barn Owls are frequently seen hunting in the day at Ham Wall to fulfil their chicks’ ravenous appetites.
Hunting Barn Owl
Barn Owls are one of the UK’s Britain’s most distinctive birds, with a heart-shaped snowy white face and underside contrasting against a golden buff on the wings, tail, and upperparts. Females are slightly larger than males with dark spots on their flanks, though it’s almost impossible to make this distinction when they are in flight!
Barn Owls breeding season is between March to August. But the birds begin the process in late winter/early spring engaging in mutual preening and cheek rubbing as part of the courtship and pair-bonding process. The male also provides the female with food; her weight gradually increases as she reaches what is known as “breeding condition.” Copulation generally occurs each time the male presents the female with food. The female will then lay up to 6 eggs, laid at two-day intervals, which are incubated for about one month before the first chick hatches. Most birds don’t begin incubating until the full clutch is laid but Barn Owls begin incubating as soon as the first egg is laid. So eggs hatch every 2-3 days and there can be several weeks difference in age between the oldest and youngest nestlings.
The female does all the incubation and the male provides all the food until the chicks are about three weeks old. Until this age the chicks do not have the ability to regulate their own temperature so require the warmth of an adult bird. Once the chicks reach the age where they have the ability to thermoregulate they also develop a very healthy appetite!
From about the age of one month the chicks are so hungry and have reached a size where they are able to eat prey in one go. Both parents are then under pressure to hunt successfully as each chick could be eating 3-4 prey items a night (about the same as an adult owl). With an average clutch size of four this means parents need to catch between 12 – 16 prey items a night just to feed their hungry chicks. The parents then need to feed themselves as well on top of all the hard work they’ve been doing to keep the family fed!
At about 13 weeks old young Barn Owls disperse from the nest site and are no longer supported by their parents. It’s no wonder that most Barn Owl pairs only raise one brood a year, though about an ambitious 10% breed twice a year and there are exceedingly rare reports of some pairs having three broods a year.
At Ham Wall the north side of the reserve tends to provide the best chances for Barn Owl sightings with day flights seen from both Viewing Platform 1 and the Avalon Hide. Owl nest boxes can be viewed from both locations so it may be possible to see ‘branched’ young sitting outside the box or on branches nearby.
From birds with voracious appetites we turn our attention to bugs which don’t eat at all once they reach adulthood but are ferocious predators in their larvae stage. Unlike their name implies the Glow Worm is actually a medium-sized, narrow beetle (like their equally misnamed American cousin the Firefly).
Glow Worm Larvae
Did you know that Glow Worms are commemorated on the Animals in War memorial in Hyde Park, London as soldiers are said to have use their light to read maps, letters, and orders in the trenches in World War 1?
Male and female Glow Worms are dimorphic which means that the adult sexes do not look the same. As Larvae both sexes are a greyish-brown with reddish spots on the outside edges of each of the segments of their body. Adult females look similar to the Larvae stage but lack the spots on the edges of the body. While adult males look the most like a typical beetle with a light-brown segmented body and the ability to fly which both the female and larvae are unable to do. At night, the female is unmistakable as she has the ability to glow.
Female Glow Worms spend upwards of 2 hours a night looking for a mate, twisting around a stem or long piece of grass to direct their brightly glowing bottoms upwards where a male might see it. Female Glow Worms are able to create this light through bioluminescence[1] and it glows constantly, though as she twists it can give the impression of twinkling as vegetation gets in the way. Males use their large, photosensitive eyes - perfect for scanning vegetation at night – to find a mate.
Glowing adult female Glow Worm
It is only the unmated females that glow as once they’ve mated, they cease to glow, and shortly after laying up to 100 eggs into damp ground they die. These eggs are only 1mm in size and the Glow Worm Larva that hatch from them are about 5mm long. It will be 2 or 3 years before they reach their full size of around 25mm long.
The Glow Worm Larvae are nocturnal predators hunting slugs and snails up to 20 times their own size and 200 times their own body weight. They catch their prey using a paralysing toxin in their bite which also dissolves flesh. Once the flesh is dissolved, they drink it up using hairs in their mouth to sieve off any parts which are too large to swallow. Feeding this way is a messy business and they use their tail to clean themselves up with particular attention paid to the face. Eating a meal this large means they can go for up to a month between feedings.
Glow Worm Larvae dedicate their lives to eating as after pupating (just like caterpillars do to become butterflies) and emerging as adult Glow Worms they do not eat as all. Adult Glow Worms are unable to eat as they lack a mouthpiece to do so. Adult Glow Worms use the reserves put on during the larval stage to spend their last few short weeks focused on their mating dance, laying eggs then dying before the cycle starts all over again.
Mating Glow Worms
To look for glowing Glow Worms choose a still, warm evening with a crescent moon (Glow Worms are less likely to glow on nights with a full moon) and allow your eyes to adjust to the darkness to be able to pick up the faint glowing of a Glow Worm. June and July are the peak months for this when females are most likely to be looking for a mate. Walking the Ham Wall Loop and around Walton's Heath are good spots to look for their glow. Maybe you’ll even catch a glimpse of a ghostly Barn Owl silently floating above a glowing Glow Worm twisting in the grass– what could be more magical?
Accessibility:
Barn Owls and Glow Worms can be seen alongside the hardstanding Main Track (old Railway Line) running through the centre of the reserve which passes Viewing Platform 1 and Viewing Platform 2. There is a hard standing boardwalk to reach the Tor View Hide. After crossing the canal there is an undulating grass path which can be muddy to reach the Avalon Hide.
For more information about accessibility please contact us on ham.wall@rspb.org.uk.
How to get to Ham Wall:
The reserve postcode is: BA6 9SX. The What3Words location is: biggest.sharpened.clots.
For further information on travelling to Ham Wall see the ‘How to get here’ section on our website: https://www.rspb.org.uk/days-out/reserves/ham-wall/
What else can I see at Ham Wall?
The sound of bird song fills the air and birds can be seen darting around collecting food to feed their young during spring at Ham Wall. The reserve is home to booming Bitterns, food passing Marsh Harriers and fishing Great White Egrets. Swifts, Swallows, Sand Martins and Hobbies glide above the reedbeds while Reed Warblers, Sedge Warblers and Bearded Tits can be heard singing from within. While strolling the secluded paths listen for the evocative call of the Cuckoo echoing across the reserve.
[1] Light created by a living thing through a chemical reaction in their bodies.
's John Crispin (Barn Owls), Steve Hughes (Adult Glow Worms), Abbie Thorne (Glow Worm Larvae)
Click on the link below to download a copy of the Ham Wall Reserve Map: