The most common bird diseases & parasites


I am particularly interested in garden wildlife which is why I did my Master's degree with a focus on "animal ecology". I am convinced that beneficial insects and wildlife are a sustainable and effective alternative to many of the products we use on our plants. I am also a passionate birdwatcher and rarely go for a walk without my binoculars.

Favourite fruit: kiwi, apple and redcurrant
Favourite vegetables: tomatoes and green beans

How can you recognise a sick bird? What are the most common bird diseases and what should you do if you find sick birds in your garden? We answer these and other questions here.

sparrow puffed up in illness
It is not always easy to identify sick birds [Photo: tuthelens/]

Like us humans, birds are afflicted by a variety of diseases and parasites. Some of these occur sporadically and generally do not have a major impact on the stock. Others spread abruptly and can take the lives of thousands of wild birds – such as Usutu virus, which caused mass blackbird deaths in 2011, or the bacterium Suttonella ornithocola, which recently led to many dead blue tits. What the most common bird diseases are, how you can recognise them and what you can do against the spread of bird diseases, we would like to present to you here in our info article.

Bird diseases: which are the most common?

Bird diseases are very diverse and can because a whole range of symptoms. It is therefore not always easy to recognise them in the first place, and even more difficult to make an accurate diagnosis. Nevertheless, we would like to introduce you to the most common diseases and their symptoms:

  • The Usutu virus became known in 2011 because it caused mass blackbird deaths in a short period of time. In 2016, there was a second major wave of infection. The virus is transmitted by mosquitoes and leads to death within a few days. Most affected animals show no symptoms but some appear apathetic and disoriented.
dead blackbird lying on ground
The Usutu virus has spread to the UK, predominately killing blackbirds [Photo: Paulpixs/]
  • In 2020, the blue tit die-off has attracted a lot of attention. The pathogen that led to this was Suttonella ornithocola. This is a bacterium that caused severe pneumonia in the infected animals. The birds seemed apathetic, were very fluffed up, some had yellowish encrusted beaks and severe respiratory distress.
  • The number of wild birds infested with bird pox has also been increasing for several years. The disease, which is also caused by a virus, occurs in a variety of bird species and is frequently observed in titmice in our country. Bird pox is easy to spot and is noticeable by hazelnut-sized growths.

If you observe sick or dead birds in your garden, you should first thoroughly clean all feeding and watering areas to prevent the spread of disease. If the cases accumulate, you should stop feeding altogether and report the findings to your nearest wild bird rescue centre.

great tits on bird feeder
If you have sick birds in your garden, stop feeding them [Photo: Vishnevskiy Vasily/]

Also, if you find a sick bird in your yard that appears weakened or apathetic, showing obvious symptoms, and you can get close to the animal, you should capture it and place it in a box with air holes. While doing this, grip the bird around the middle of its body to prevent it from injuring itself by flapping its wings frantically. In any case, gloves should be worn to protect against beaks and claws. Then place the box in a quiet, dark place and contact a veterinarian or a suitable foster home.

nursing sick robin with syringe
Sick birds need professional help [Photo: kai foret/]

Note: As a layman, you should not attempt to nurse the bird to health yourself. Also, do not give him water or food because the animals can choke. Wild bird care requires a lot of experience and knowledge and therefore usually goes wrong if not done by experts. By the way, the same is true if you have found an injured bird.

The most common bird parasites

Parasites are also a problem for wild birds. Some can be seen with the naked eye, others are so small that you have to go by the birds’ symptoms. We present the most common parasites in wild birds below:

  • Featherlings are small plumage parasites that lay their eggs in the feathers of birds, where they feed on dander and feather components. As a result, the birds experience severe itching and scratch a lot. As a result, the birds usually look unkempt and sometimes have severe plumage damage. In addition, they often appear weakened because they suffer from sleep deprivation due to the constant itching.
three bird lice unter microscope
Bird lice are often so small that they are only visible under a microcope [Photo: Pavel Krasensky/]
  • The louse fly, unlike the small feather flies, is several millimetres in size and therefore easily seen with the naked eye. The parasite also attaches itself to the plumage of birds but bites into the skin and feeds on the animals’ blood. Louse flies often specialize in certain bird species. One of the most common representatives is the swallow aphid, which attacks, for example, flour swallows and smoke swallows.
magnified louse fly on feather
Louse flies, or keds, bite into the skin of birds [Photo: Pavel Krasensky/]
  • Trichomonads are single-celled organisms that spread by direct contact between birds and can infect many birds in a short time. The pathogen Trichomonas gallinae first caused mass mortality among greenfinches in summer 2009. Affected birds exhibit frothy saliva, great thirst, and a greatly diminished flight response.
  • Bird mites are burrowing mites that infest the face, legs, or cloaca of birds. The parasites can be recognised by whitish, scabby deposits they because in the affected regions. Here, too, the birds scratch themselves and sometimes even travel feathers.

As with the above diseases, the treatment of avian parasites is almost impossible for laymen. Louse flies could still be picked off with tweezers and crushed like a tick but once the bird is weakened enough to be captured, it will still need professional help, so the same instructions as before apply.

Is a fluffed up plummage a symptom of disease?

A fluffed up plumage serves mainly to protect against heat loss. The extra air that accumulates between the fluffed springs has an insulating effect and makes it more difficult for the body to lose heat to the environment. In winter, this is quite normal and not necessarily a because for concern. However, in summer and warm temperatures, fluffed plumage may very well be a sign of disease, as sick birds are often hypothermic and cold. However, sick birds often show additional symptoms. They pull their heads close to their bodies, close their eyes slightly, and are often slow to flee or do not flee at all when approached.

abnormally puffed up chaffinch
This chaffinch is morbidly fluffed up [Photo: Lillian Tveit/]

How to support birds against diseases and parasites?

Bathing in sand to get clean sounds strange to us at first but for birds it is an important part of plumage care. With a lot of shaking and wing flapping, parasites are removed in this way. Therefore, a sand bath in the garden can be of great benefit and is quite easy to make yourself: you can simply fill a trivet or bowl with sand and place it in a place that is as sunny as possible and safe from cats.

close-up of sparrow sandbathing
A sparrow taking a healthy bath in the sand [Photo: Vishnevskiy Vasily/]

Note: Another bizarre practice of plumage care in birds is known as anting. In the process, the birds brush living insects – mainly ants – through their feathers. The secretions released as a result, such as formic acid, act against bacteria, fungi and other harmful organisms there.

Other hygienic measures that you should carry out yourself also include regular cleaning of your bird drinkers and feeders. Especially on hot days, these can otherwise quickly turn into breeding grounds for parasites and pathogens. Since many birds gather there, numerous animals can become infected in a short time.

Besides diseases and parasites, birds in the garden often have quite other problems. Domestic cats, for example, are a real danger that is often underestimated. How cats and birds feel comfortable at the same time in the garden and what you should pay attention to as a cat owner and bird lover, you will learn in our dedicated article.

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