As breeding season reaches its midway peak in the northern hemisphere and as autumn morphs into winter in the southern one, your local bird populations will likely be congregating around your feeders in greater numbers, either teaching the new kids on the block where they are or gathering en masse as cold weather builds and food in their natural habitat becomes increasingly harder to find. It is this proximity to one another that can spell disaster if there are great conditions for bad things to happen.

Many species who visit feeders are gregarious — sociable — like most sparrows and tits and some finches, then there are those who are solitary or only hang out in their breeding pairs. Whatever the configuration, the one thing they will all have in common when coming to your feeder is — your feeder.

Think of it like a fast-food joint that has a special all-you-can-eat offer on; finding somewhere to sit is chaotic and you’re constantly bumping into people. Our recent global brush with a certain pandemic should have impressed upon us what can potentially happen when there are lots of people in one place; throw any disease into the mix and you have a planet-sized petri dish in which various organisms will absolutely go crazy with all those hosts to latch onto.

Now imagine the fast-food joint is very sticky, there are discarded food wrappers all over the place with no one clearing it up and in the corners there are plies of food going moldy and starting to smell — more opportunities for other nasties to propagate. That joint should be shut down by the authorities and its proprietors never allowed to be in catering again; but in the meantime, the damage is being done.

Viruses, bacteria, mold and fungi are having a field day and happily adorning our bodies, and we are taking those germs home with us and leaving them all around our house and passing them on to friends and family when we see them.

Analogies begone – what happens at your feeder can be far more dangerous for birds than anything we usually find in a filthy burger bar. Birds don’t get the chance to go to the doctor for some meds and get some rest. We need to be vigilant to make sure our feathered friends stay healthy and well-fed, and that involves us doing two very simple things – know the signs and clean your feeders.

Diseases and their symptoms

Salmonella: one of the most common diseases birds can catch – usually fatal. Salmonella is a bacterial infection that can be transmitted from bird to bird through contaminated feeders via their droppings and saliva. It can survive on feeder surfaces for several weeks in a dry environment, and several months in wet ones.

Symptoms: lethargy, diarrhea, and a lack of appetite; infected birds can become so weakened that they are unable to fly or perch, which means a bird with this disease is less likely to fly away when you approach.

Avian pox: a viral infection – generally not fatal but will cause significant discomfort and distress. Fatality can occur via secondary causes. The virus is highly resistant and can exist for long periods on surfaces.

Symptoms: birds tend to behave and feed normally, if they can – the virus causes wart- or tumor-like growths, often on the bird’s head around the eyes or beak, and on their legs and feet, sometimes even their wings.  The growths are gray, red, pink or yellow in color, and can become very large leading to restrictions in vision, eating and movement; which in turn makes birds highly vulnerable to predation, starvation, and can also lead to secondary infections.

Trichomonosis: also known as canker in pigeons and doves and frounce in birds of prey. Caused by a parasite that doesn’t survive long outside the host but nevertheless has led to some severe outbreaks in the past, causing rapid declines in the mid-2000s in British finches. It is passed via contaminated water or regurgitated food.

Symptoms: due to the disease attacking the throat and gullet, birds show difficulty in swallowing, often with labored breathing, as well as wet plumage around the bill from drooling saliva or regurgitated food they can’t swallow. Sometimes the neck may also swell. In general, birds will be lethargic with fluffed-up plumage, and they can be ill for several days or even weeks.

Aspergillosis: a respiratory infection contracted by inhaling fungal spores found in contaminated feed or feeder debris. Aspergillus fungus exists everywhere in our environment, particularly in soil, nesting material and moldy food, and it’s quite resistant to disinfection. Seed-eating birds are more prone to this as the seeds generally lack Vitamin A which is essential in keeping immune systems healthy.

Symptoms: difficulty breathing, lethargy, and loss of appetite. If left untreated, the infection can lead to death.

Colibacillosis: caused by the bacterium E.coli, this affects a wide range of garden bird species and makes it harder for them to digest their food which can lead to other complications. Most often seen in domestic poultry, nonetheless it can easily get into the external environment, and in acute cases will cause septicaemia and death.

Symptoms: respiratory distress, fluffed up feathers, poor appetite.

Bird flu / avian influenza: the current virus strain is known as HPAI, where the HP stands for Highly Pathogenic. It spreads through contact with infected saliva, nasal secretions or droppings.

Symptoms: swollen head, closed and excessively watery eyes, unresponsiveness, lack of coordination and loss of balance, drooping wings and/or dragging legs, twisting the head and neck, respiratory distress; the list is long and upsetting. The gravity of the current situation with bird flu can’t be overstated, and there are serious concerns that this disease will lead to species extinctions very soon as the combination with other pressures like habitat loss and pollution the birds are already under is just compounding the issue.

Garden birds are, however, far less at risk than other wild birds like seabirds, whose colony lifestyles are seeing devastating numbers of deaths. It is still vitally important you are aware of the symptoms and report any dead birds you see.

How to fight disease

All of the above are very nasty diseases that will cause a good deal of distress to the birds at your feeder, if not eventual death. The good news is that ALL of them can be thwarted by simply keeping your feeders clean, and if you spot any symptoms then take your feeders down immediately and inform your local wild bird specialists. After that point, listen for the all-clear from them or keep your feeders down for at least two weeks.

The best way to clean a bird feeder is to use a solution of one part bleach to nine parts water. Empty the feeder and take it apart as much as possible, then soak the feeder in the bleach solution for at least 10 minutes. Use a brush to scrub away any debris or mold, and then rinse the feeder thoroughly with clean water. Allow the feeder to air-dry completely before refilling it with fresh seed. This is important – drying manually with a towel will always miss spots, and mold and fungus only needs a tiny amount of water to fester.

Lastly, as some of these diseases can also be passed on to us, be sure to always wash your hands thoroughly before and after handling feeders or food and avoid touching your face or mouth while handling them.

Next time you are admiring your garden birds, take a few extra seconds to note any erratic or unusual behavior, and if you can get a good long look at any of the visitors, see if you can spot any disfigurations or unhealthy-looking symptoms like excessive feather loss, lumps or growths. Not only will paying closer attention help you recognise bird behavior which makes you a better birder, it will benefit the birds themselves, helping to prevent the spread of disease among their populations. And remember — keeping that feeder clean is a vital part of being a responsible bird lover.