A Week on the Estate: Winter Lingers, Owl Insights & Expert Ringing

“At South Ormsby Estate, we talked about tawny owl nest boxes initially then added barn owl boxes too. Barn owls moved in straight away and two or three tawny boxes were occupied over time. It was a slower start with the tawnies because these birds like good natural sites and they had plenty to choose from. Currently, the Estate has 10 tawny owl boxes, five barn owl boxes and one kestrel box.

“Barn owls are an easy win with the farming community. Each pair needs 10ha of rough grassland. One of their challenges is that voles and mice go through a 3-4-year boom-bust cycle. They’re also affected by climate change, and have to manage both dry grass and flooded ditches.

“Tawny owls like a ‘vicarage garden’, a dense, wooded area. They like to hunt songbirds and small mammals in shrubs and flower layers, and they’ll also take young rooks when they’re branching. They’ll get them at dusk and they’ll drop on them rather than chasing. We’ve found ducklings predated by tawnies too. They’re very opportunistic. The best tawny site I’ve seen in Lincolnshire was near a former railway line in Louth. The owls were predating on blackbirds in mature, dense garden shrubberies and produced five chicks.

“The tawny is bigger and hardier with shorter wings. They’re designed to hunt in small spaces and drop on to prey. Barn owls hunt over more open terrain and glide in. Barnies have offset ears for 3D ranging and a wing profile that reduces noise from flapping. Tawnies average 500-600g in weight, compared to 300g for a barnie. Both birds are sedentary to varying degrees. Barnies tend to breed within 20km of their point of origin. We ringed a tawny breeding in the box it was born in 10-12 years earlier.

“Tawny owls have spats in early winter as the youngsters are obliged to find their own territories. You’ll hear the call and response – the male ‘kerwit’ and female ‘whoo’ sounds.  Like some teenagers, they have to be encouraged to leave home and then they don’t move far! The barn owl has a ghostly screech.

“Barn owls like grassland, and that can include streamside or waterside locations. Cut hay meadows in autumn present the most wildlife. They prefer small mammals and it’s rare for them to eat birds. Sometimes they exhibit niche skills. They’re known to brush the tops of reeds to flush prey and I came across one that took starlings from a reed-bed roost.

“Barn owls hate the wet as it reduces their ability to fly. In persistent rain, they’ll shelter in nesting boxes in preference to trees. If you want to encourage barnies, it can be useful to provide both nesting and roosting boxes. They’re built for temperate climates and the UK is right on the edge of their range. They breed earlier and more often in Southern England. My friend in Jersey rings them in April and May, whereas it’s June and July in Lincolnshire.

“Barn owls breed more quickly and produce large broods in favourable conditions. Tawny owls have smaller broods but live longer. As a rule of thumb, an adult must fledge three chicks to maintain a stable population level.

“Ringing tells you how long birds live. We monitor adult survival rates between seasons and find out whether juveniles thrive and breed. It revealed, for example, that too many song thrush juveniles weren’t feeding well enough to survive the winter and breed in spring.

“Typically, we mark and recapture the same adults year after year. With puffins, one-third of captured birds have rings on. Once they reach four or five years, they have a survival rate of 0.9.

“When it comes to handling wild birds, some species are more relaxed than others. They have species-specific defence mechanisms. Woodpeckers scream a lot! Generally, using a bag to keep the bird in darkness calms them. They don’t have emotions as such but their priorities differ. Blue tits, for example, can be caught multiple times whereas sparrows become wary. It may be that the blue tits are more committed to feeding.

“To get accredited as a bird ringer, you train with a mentor. There are various modules on the ringing licence. It can be as specific as nestlings in small boxes or owls in bigger boxes. Getting licensed for more specialised work can require a few years of work. Netting sea birds requires an ability to differentiate between young and adults.

“It’s satisfying work. I’m licensed to ring by myself and I make owl boxes. I also got into sea birds as I love islands and remote places, particularly when I’ve got a good reason to go.

“Ringing gives us so much information on these amazing animals. It’s essentially how we found out that swallows over-winter in Africa. Edward Jenner, the creator of the smallpox vaccine, was also a naturalist who tied cotton to swallows’ legs to see which returned to the UK year after year.

“I conduct bird-ringing under licence from the British Trust for Ornithology. If your readers would like to get involved, there’s some useful information HERE.”

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