St Nicks

Centre for nature and green living

Spotlight on… Tawny Owls

The Tawny Owl is one of Britain’s most familiar species of owl and has been heard throughout our forests, woodlands and parklands for thousands of years. Our relationship with owls has often been a complex one; in previous times they were thought to have been omens of death and harbingers of doom. Associations with black magic and the full moon (some theories propose that Tawny Owls are more active during a full moon) have only increased unwarranted suspicion. Their role in folklore as witch’s familiars has also not helped the reputation of the misunderstood tawny owl; a creature that, since before the last Ice Age, has played an important role in Britain’s woodland ecosystems.

 

(British owl species, including the Tawny Owl. Images from RSPB Website: https://www.rspb.org.uk/birds-and-wildlife/wildlife-guides/bird-a-z/owl-family/)

Owls are one of the most distinguishable bird families; their rounded head, small, hooked beak and large eyes which come in a variety of colours, sets them apart from other bird species. Interestingly, some sources suggest that the colour of an owl’s eyes is reflective of the time of day that it hunts; the Tawny Owl’s jet black eyes indicate that they are primarily nocturnal. Similarly owls with sunny yellow eyes are thought to be day flying and owls with orange eyes, mirroring sunrise and sunset, are associated with dawn and dusk (crepuscular). This is an unproven theory but other, confirmed scientific findings provide an insight into the truly amazing anatomy of owls. Eye shape and size often indicates what time of day birds are most active. Larger corneas and pupils allows greater amounts of light to enter the eyes— a helpful evolutionary feature for nocturnal creatures. The size of an owl’s eye also influences the brightness of the image produced. Humans, with a smaller pupil produce an image that is 2.7 times darker than that of a Tawny Owl. The ability to brighten images greatly aids owls but is not without its limits. Dense woodland is a very typical Tawny Owl habitat, however, the low levels of background illumination for dense woodland canopies falls below what is required for an owl to hunt. With reports of Tawny Owls crashing into trees it is perhaps not surprising that they are more likely to fly under the bright light of a full moon. This may also attribute to the Tawny Owl’s hunting style.

St Nicks woodland at night (photo taken by Lewis Outing)

The Tawny Owl is one of the more sedentary species of British owl. Unlike the Barn Owl which actively hunts for its prey by flying across fields, the Tawny Owl is more of a sit and wait predator. Perching on tree branches, Tawny Owls will wait for their prey to come to them; a tactic that is probably less likely to end in broken bones for the Tawny Owl (bone fractures are more common in owls, typically night flying, than day flying birds). The Tawny Owl shouldn’t have to wait too long as there’s a broad range of potential meals on the table….or the forest floor! Adaptable creatures, the habitat that a Tawny Owl chooses will change the species they predate and it will change how they hunt. Tawny Owls inhabiting more open spaces are more likely to actively hunt for their prey from the air.

Goldfish swimming in Tang Hall Beck

Goldfish swimming in Tang Hall Beck

A Tawny Owl’s variable diet can range from the likes of fish to mallards! Goldfish are on the menu for more urban Tawny Owls, often stolen from the garden ponds; though Tang Hall Beck was once home to a rogue goldfish (probably a local’s liberated family pet) which may very well have been fodder for a passing Tawny Owl. Charts show that in countryside habitats Tawny Owls will mainly dine on mice, voles and other rodents, whereas urban Tawny Owls will primarily feed on birds.

However sometimes the prey will fight back! In Eric Hosking’s book, simply titled: Owls, (Eric was one of the pioneering wildlife photographers at the time who actually lost his left eye to a very territorial Tawny Owl) he details the Tawny Owl being mobbed during the day by the likes of blackbirds and finch and tit species. He suggests that this a ‘fire drill’ for day flying birds, to ensure they recognise the face of their potential predator. Though the Tawny’s mottled browns, whites and greys help it to blend in with the tree trunk it roosts in, their camouflage is apparently no match for the keen eyed birds who will make quite a raucous; attracting attention and warning their fellows.

We have previously thought Tawny Owls to be a stable, thriving population so there is still limited research into their numbers and lifecycles. However new data from the Breeding Bird Survey (BBS) suggests that a 27% decline in Tawny Owls has occurred since 1994. The BBS and the British Trust for Ornithology (BTO) have launched two new surveys to further investigate the decline of the Tawny Owl which has been dropped from a green to amber listed conservation status. This has sparked worries over the future of the species because presently no-one knows why the population has declined and there could be any number of reasons for this. During the Mesolithic times it was predicted there were 160,000 Tawny Owl pairs which is a far cry from today’s population which currently rests at around 50,000 pairs. This is probably due to the change in habitats; after the last ice age, when the ice caps were retreating, birch and conifers began to establish themselves. A succession of other tree species followed, leading to most of Great Britain being covered by woodland; the perfect ecosystem for Tawny Owls. However when humans began to make the transition from the hunter gatherer lifestyle and move towards agricultural practices, ancient wildwood was cleared to make way for farmland and in more recent times urbanisation has led to continued decrease and fragmentation of natural habitat. The loss of habitat may have attributed to the Tawny Owl’s continued decline. Because Tawny Owls are so adaptable to change (shown through their diet) the decline was not noted until very recently, having previously being thought of as been of no concern for conservation.

Woodland at Heworth Holme

But it’s not all bad news for the Tawny Owl and you don’t have to look far too happen across our nocturnal, feathered friends. During our Meadow Keepers evening sessions at Heworth Holme wetland meadow and Fulford Community Orchard, our dusky scythe sessions have been punctuated by the haunting hoots from quiet woodland fringes. Proof, that even in the most urban and built up areas (Fulford Community Orchard is located next to the car park of York’s Designer Outlet and Heworth Holme is nestled amongst residential housing) wildlife can thrive. At Heworth Holme in particular we know that the Tawny Owl heard is a regular of the woodland which is unsurprising given how territorial Tawny Owls are. And it’s not just at dusk either; Tawny Owls have been heard during our Friday morning, Greening up Heworth Holme sessions. These daytime hoots of a Tawny Owl have caused much confusion and bemusement to our volunteers! No one knows for sure why owls call during the day, but online forums suggest that the British Birds Rarities Committee are keen to undertake investigations to find out how widespread this phenomenon is and why it occurs. Other sources describe that the time of day that owls are most active is much more intrinsic than we might have first believed with factors such as habitat, the time of year and weather all having an impact on the habits of owls.

As previously mentioned Tawny Owls are very territorial. Once young Tawny Owls have flown the nest they will find their own territories where they will stay for the rest of their lives. This new territory won’t be a million miles away from the site where they hatched. Tawny Owls lay their eggs (two to three, pale white in colour) between the months of March and May. These will be incubated by the female for around a month, while the male delivers her food during this period. The hatched chicks will then fledge the nest between 35-39 days later, find territories of their own and as little as a year later when they become fully mature, start looking for a mate themselves.

Owl box built and hung by St Nicks woodwork group

And it’s not just our Meadow Keeper’s project sites where Tawny Owls have been on our minds; St Nicks’ own Ecotherapy Woodworking group have been trying to encourage Tawny Owls to use the reserve by putting their new-found joinery skills to work. The group have worked throughout the spring and summer and many of their projects have been for the benefit of wildlife. They have constructed hedgehog homes, bird and bat boxes and last, but by no means least, two owl boxes which were hung in the woodland this July. The finished products can be seen in the photos to the right. We are immensely impressed with our new owl boxes; for some of the Ecotherapy volunteers this was their first ever woodworking project! And our Wildwatch team will keep their eyes peeled for any signs of inhabitation over the coming months. They’ll be looking out for something called ‘whitewashing’, owl poo decorating the tree trunks below favoured perches and owl pellets, the less palatable regurgitations of an owl’s meal; primarily fur and bones (which are great fun to dissect!) Tawny Owl pellets are unique, having a furry appearance that is a bumpy, irregular shape, tapering at one end and are grey in colouration. Tawny Owl pellets are a lot more delicate than other species and are liable to break into pieces.

With our new owl boxes and continued management of woodland habitats on the reserve (see January’s Blog on Woodland Understorey for more information about woodland management), St Nicks should provide a haven for Tawny Owls and their prey by having a mosaic of micro habitats in the woodland. Dark, closed off canopies for Tawny Owls and other shade loving critters to more open, coppiced areas where sunlight can enhance the woodland ground flora.

And not only can you look out for signs of Tawny Owls in your local area you can survey for them too! The British Ornithological Trust has set the Tawny Owl Calling Survey which can be done anywhere, for 20 minutes in the evening from now until the end of March. The call of the Tawny Owl is very interestingly the classic “ti-wit-to-wooo” (often heard in the cinematic world in scenes of suspense or to accompany a spooky woodland scene of a horror film) that most people associate with owls. But this is actually the combined calls of two different Tawny Owls’- the male and female. The male makes the haunting “wooo” and the female makes the “ti-wit/kewick” sound. Participants in the survey have to listen out for these calls at least once. The results of this survey will start providing some insight into the decline of tawny owls.

Things truly have changed since early relations between Tawny Owls and humans some hundreds of years ago. From being treated with suspicion to having whole surveys dedicated to finding out more about these nocturnal creatures; the Tawny Owl’s story is certainly an interesting one.

 

30 October 2018 | Categories: Spotlight on... | Tags: ecotherapy, tawny owl, woodlands