Half dozen new hoots

Outdoor Living

RECORD BREAKERS The Mayo barn owl chicks have been fitted with leg rings so they can be tracked and recorded.  Pic: Michael Kingdon

Mayo nest box sees bumper brood of six beautiful barn-owl chicks

Country Sights and Sounds
Michael Kingdon

Remember Nathy Gilligan’s barn owl nest box?
It has proven a hit with the local owls once again. This year seven eggs were produced. Of these, six hatched, and all six owlets are well on their way to maturity. Working with Birdwatch Ireland, John Lusby has been monitoring barn owl populations here in the west for several years. I was able to meet up with Nathy and John on the morning the owl family were to be fitted with numbered leg rings, which will enable the birds to be tracked and recorded.
The first thing we spoke about was family size. While not unheard of, seven eggs is a quite a clutch for an Irish barn owl. The previous record for the number of chicks to fledge from a County Mayo nest was four, so to have six new adults is a real boost to the local population. I was surprised to learn how few breeding pairs there are within the county, and how these special birds have been declining in number for decades.
So what challenges have barn owls been facing? And what factors have contributed to the rearing of such a strong and successful family?
As far as challenges go, we needn’t look far. For one thing, wet feathers do not help when it comes to hunting. While warmly insulating when dry, owl feathers lack the waterproofing found on many other birds. Wet feathers reduce drag efficiency, which makes flying far harder work.
And anybody who has watched an owl gliding over fields in the gloaming will have been impressed by that perfectly silent flight, which is the result of feather design. The leading edge of flight feathers are broken up into numerous soft ‘fingers’, each of which is composed of many smaller fibres. Each of these fibres is then divided again, creating an extremely soft edge. The trailing edge of those same feathers is highly flexible, which absorbs most of the little sound produced. When wet, the feathers create far more noise and reduce hunting strike rates considerably.
After studying the sound reducing qualities of owl feathers, scientists working with biomimetics are developing low-noise blades for wind turbines, virtually silent fans and aircraft parts that dramatically reduce turbulence! There is so much to learn.
Other challenges include the widespread use of rodenticides. Poisoned rats and mice become stupefied and disoriented, and are easy prey for a hungry owl. The consequences of secondary poisoning are obvious, not just for the bird which finds the near-dead animal, but also for the nestlings which will eat it.
A ten-year-old study coordinated by John Lusby found that Irish barn owls contained about four times as much rodenticide as owls in the United Kingdom, a result of the Irish predilection to poisoning everything that doesn’t suit. This mindset has been challenged in recent times and again we are learning to look after our wildlife much better.
So why, with this particularly wet year making for difficult hunting conditions, has the Gilligan nest box been so successful?
One great asset has been the supplementary feeding programme that Nathy has introduced. He showed me his store of frozen day-old chicks, a byproduct of the poultry industry. At the time of hatching, Nathy explained, the chicks are inspected to determine their sex. Females are kept alive and go off to spend their lives laying our breakfast eggs, while the males are killed en masse and sold as pet food, or in this case, owl food.
Another unexpected bonus has been the arrival of the greater white toothed shrew. This ferocious mini beast has only been in the country for a few years, yet has contributed to the near demise of our own pigmy shrew and likely to the disappearance of our native wood mouse too.
White toothed shrews will reproduce as fast as you like. There are loads of them here, and as fast as they can be caught they are being replaced. When we dissected an owl pellet from below the Gilligan nest we found nothing but the remains of these animals. (The skulls are easily identified, being conical in shape and quite distinct from any of our native animals.)
With their rich diet, this owl family have had a great start to life.
Yet we have room for many more owls in this part of the world. The entire Irish population is somewhere between 400 and 500 pairs.
We look forward to seeing the new family out and about. We should give a big shout to to all who are working hard to keep our owls alive.

Michael Kingdon’s earlier article on Nathy Gilligan’s nest box, ‘Build it and they will come’, was published on March 3 and is available here