What is a zoonosis? Unfortunately, it's not a fun outing to Taronga, but instead any disease that infects or is carried by animals, which can also infect or be spread to people.
 
An estimated 60% of human infectious diseases around the world are zoonoses. And there's one that has the potential to do a lot of damage to chooks and humans: Bird flu, or Avian Influenza (AI), which has its reservoir in wild birds (they carry it without getting sick). AI comes in multiple varieties including Highly Pathogenic Avian Influenza, (HPAI). An example of HPAI is H5N1, which has lately smashed everything from parrots to penguins on every continent except Australia. 
 
Preparations for the worst are being made. What preparations can owners of backyard chooks make?
 
NSW has an excellent fact sheet here: https://www.health.nsw.gov.au/Infectious/factsheets/Pages/avian-influenza.aspx
 
...with the main take-aways being that bird flu is endemic in wild birds; that is, they carry it in their bodies all the time, and may not show any symptoms or get sick from it, but when they mix with domestic birds, such as your free-ranging leghorns, or contaminate your backyard by coming down to your birdbaths or chook feed dispensers, the virus can be passed to you, not to mention your budgie or your bantam.
 
What to do? Rehome your birds? If your household has immunocompromised people in it (eg young children, the elderly, anyone on chemo or other immunosuppressing medications) this is a valid step. Not just on account of AI, but other endemic zoonoses such as psittacosis, aka parrot fever, which has frequent outbreaks in the Blue Mountains due to our love affair with feeding native species. 
 
If you've ever worked at a big poultry producer, you'll know pet birds at home aren't allowed, because of biosecurity, ie the risk that your pet bird may be invisibly carrying something nasty. Poultry farmers have had the experience of driving vehicles through troughs of disinfectant, to keep contaminated soil out, and of performing a complete shower and change of clothes when passing in or out of the buildings.
 
This kind of barrier between your kitchen and backyard may not be practical. But you can try to approximate it by regularly washing hands with soap and water, wearing coveralls, and disinfecting your gumboots before and after attending to your chooks, even if you don't go the full PPE including P2 mask.
 
If you have a birdbath, situate it well away from areas that your chickens have access to. Fully emptying and disinfecting any food and water vessels every day is ideal. Always choose water containers that can be scrubbed and sterilised over a pond or waterfall which can never be cleaned and which will attract wild waterfowl.
 
Use netting, covered water and feed dispensers, and rat-proofed coops to reduce the chances of wild bird contact and/or contamination. 
 
Be careful around wild birds - enjoy watching them but don't encourage them to land on you, come into human-frequented spaces, or share your food.
 
Love your chooks and your aviary birds but don't kiss them!
 
Keep your annual human flu vaccination up to date. This reduces the chances a bird flu virus and a human flu virus can coexist in your body, potentially swapping genetic material with each other to mutate into the superflu that causes the next pandemic.
 
And if you notice a swathe of sudden deaths, coughing and sneezing, or other symptoms in your backyard flock, refer to this Bird Life Australia handout: https://birdlife.org.au/wp-content/uploads/2024/09/Avian-Influenza-Fact-Sheet-Sep-2024.pdf
 
...and AVOID, RECORD, & REPORT to the Animal Disease Hotline.

​Do you know what's in your soil? Or, more to the point, what's in your chickens?

In 2019, the Sydney Morning Herald reported that the most lead-polluted areas in the Greater Sydney area included the Blue Mountains, with 29% of mountains residences exceeding safe levels.

Where natural background levels are 20-30mg/kg, Blue Mountains average lead concentration in the soil was found to be 287mg/kg.

It might be simple enough for flower-fancying gardeners to whack on gloves while they're trimming the roses, and take away the toddlers' mud pies before dirt hors d'oeuvres can be eaten. But what about free-range backyard chooks? Often, if there's lead in the soil, there's also lead in the eggs.

Lead is absorbed mainly through the gastrointestinal tract in chickens. Chicken bones serve as the long term storage site for the toxic heavy metal. Lead affects the red blood cells, the kidneys, and the nervous system. You might notice incoordination, regurgitation, or weakness. But you also might not - some chooks can absorb terrible amounts of lead without showing any signs - including not slowing down on the egg production.

In a study reported on by the ABC's Conversation in 2022, backyard hens' eggs were found to contain 40 times more lead on average than shop eggs  ( https://share.google/nWVvKSY54BJcBwHMM ) and almost half the eggs analysed posed a threat to human health.

Sources of lead in the backyard can include contaminants from industrial processes of decades or centuries ago, lead paint used on older houses, residues from the days of leaded petrol, lead pipes, lead sinkers, lead light windows, and proximity to railway lines.

Soil lead testing kits are available at hardware stores, or from online suppliers.

What about testing your hens? Vets can test blood lead levels in chickens. Not all chickens with high levels of heavy metals will show clinical signs. Affected chooks can start a series of injections for chelation therapy - but they then have to go to a safe area of the garden, or be rehomed if you're unable to have your own backyard decontaminated.

For food safety, if a child is eating one egg from a backyard chook per day, the levels of lead in the soil would ideally be less than 117mg/kg - and if you aren't eating the eggs, for the health of the chook, less than 166mg/kg is recommended.

Investigating lead levels in your soil and your chooks may bring peace of mind when it comes to eating eggs sourced from your backyard. 

​Springwood, maximum 13 degrees. Brrrr!

Who wants to put their pet birds outside in winter? In the mountains? You'd have to be crazy, right?

Actually, you'd be crazy not to. And that's because of the importance of direct sunlight to your bird's vitamin D levels.

Vitamin D is essential for the absorption and utilisation of minerals including calcium. Human residents of the Blue Mountains may be used to their GP's exhortation to get more sun, especially in winter. Without enough vitamin D, laying birds can show reduced eggshell thickness or eggs with no shell at all. Growing birds can show osteodystrophy. All can show clinical signs of hypocalcaemia including seizures, and soft bones prone to deformity or fracture.

Backyard chooks will usually get plenty of direct sun. When it comes to caged birds, however, setting their cage near a window won't quite be good enough, since it's the ultraviolet part of the spectrum they need, which can be filtered out by the glass.

UV-B converts provitamin D in the skin to cholecalciferol, or Vitamin D3. If it's really freezing outside, could you use UV-B fluorescent bulbs for some fake sun therapy? Absolutely! 30 minutes of direct sunlight per day should be sufficient.

Couldn't you just supplement with vitamin D in water or food instead? This can be tricky when it comes to under- or over- dosing. Macaws can get vitamin D toxicity (mineralised kidneys) at lower levels than other birds (1000 IU/kg). Dosages vary, and many formulated diets already contain extra fat-soluble vitamins including vitamin D.

Ideally, regulation of calcium and vitamin D would happen with variety in the diet, optional grit available at all times, and plenty of direct sun. It is possible to get vitamin D toxicity by oversupplementing, but not via too much UV-B! (Sunburn remains possible, keep in mind).

Whether you go for the UV-B lamp or the wintry mountain sunshine, taking care of your bird's bones will be worth it. Happy solstice!