Those out at night around Margaret River encounter an abundance of night birds – the small, familiar Boobook and extraordinary Tawny Frogmouth and perhaps the diminutive, cute Owlet Nightjar. Ghostly Barn Owls are caught in headlights as they hunt mice in farmland. Until recently few knew this region is also a stronghold for the Masked Owl Tyto novaehollandiae, a large forest relative of the Barn Owl who can prey on animals as large as possums and quenda.
The Masked Owl of south eastern Australia is considered endangered in many areas. Our SW WA Masked Owl, whose genetic relationship with other Masked owls is as yet unknown, has a conservation status of Priority 3: ‘known from several locations, do not appear to be under imminent threat’. However, it is so little known that even its nest and eggs have yet to be described.
Margaret River a Masked Owl strong-hold
A private study by Nature Conservation Board members Boyd Wykes and Steve Castan has revealed that Masked Owls occupy much of the Capes region, each life-long pair hunting an area about 6 km across. Their annual cycle starts with high activity in autumn-winter when territorial and pair-bonding screams are frequently heard but often mistaken for fighting Brush-tailed Possums. This is followed by a quiet period through to summer when nesting in hollows of ancient marris. By observing fledglings being fed in summer-autumn and collecting regurgitated pellets, we know that our Masked Owls are doing well on a diet of rabbits, rats and mice associated with people.
Listen to a dependant, immature Masked Owl during a food exchange, recorded near Margaret River. The parent calls once, near the end, plus a fox.
Now you see me, now you don’t
From their roost and nest hollows in blocks of quality forest, our Masked Owls range out each night to hunt rodents around farmyards and the chook pens of peri-urban housing. That finding has raised alarm bells. Alerted by research showing that Boobooks are succumbing to secondary poisoning from eating rats and mice as they die from baits (rodenticides), three Margaret River region Masked Owls have also been tested by ECU, one found dying from unknown cause and two hit by cars. All three proved to have rodenticide exposure at lethal levels. Just as we were finding and celebrating our region as a strong-hold for this enigmatic, charismatic nocturnal vermin killer, we have also discovered that we are killing them through secondary poisoning from rat baits.
Silent Night: Rat poisons are killing owls and other nightlife
In a PhD study at Edith Cowan University, Mike Lohr used Boobooks as a readily accessible species to test for levels of rodenticides in dead birds collected from across the SW, including from Margaret River. The results were shocking, with 74% of birds containing poisons. Even where not directly resulting in death, many levels were sufficiently high to result in death from apparently unrelated factors such as vehicle impact, disease and starvation.
Sadly, this finding was not unexpected because problems arising from second-generation rodenticides have already been identified throughout the world. Many day as well as night birds and mammals eat rat poison and prey on live and dead rats and mice. Once ingested by rats, second-generation poisons can go on killing anything that eats them for many months. Dogs, cats and children have been poisoned by direct contact and consumption. Some countries have banned or restricted use of the same second generation poisons that are sold without regulation by Australian supermarkets, hardware stores and farm suppliers.
More about Mike Lohr’s research findings can be found in the following research papers:
Organisations such as Birdlife Australia are tackling the issue at a national level to appropriately manage sale and use of rodenticides now that we have the proof that these are a threat to Australian native fauna, both directly and through indirect poisoning via baited, dying prey.
At the local level, Nature Conservation has formed a Rodenticide Action Group. The main objective is to stop the use of so-called ‘second generation’ rodenticides that are killing off our Boobooks, Masked Owls and likely many other nocturnal wildlife. The Group is mounting a campaign to get distributors on board to restrict sales or at least provide informed advice to customers about the worst of the rodenticides, and to get the message out to customers – pest controllers, householders and agriculturalists.