The Elephant in the Garden: why are British bird numbers falling?
Bird feeding and bird numbers
The feeding of wild birds in domestic gardens is one of the most popular types of human-wildlife interaction in the world, and the UK is no exception (Clark, Jones, & Reynolds, 2019). A study of British homes found that 64% of households across rural and urban areas in England put food out for birds (Davies, Fuller, Dallimer, Loram, & Gaston, 2012). There are a whole range of reasons why people devote time and money to feeding the birds they see in their gardens. These include caring about bird survival, educating children, the joy of nurturing and caring for something, a longing to connect with nature, and just the simple pleasure of doing so (Clark, Jones, & Reynolds, 2019). The common thread through all of these reasons is that feeding birds gives you a good feeling and is a positive thing to do. But there’s another side to the story; an unseen “elephant” in the garden that is causing problems for wild birds.
It’s very apparent that Britain’s wildlife is in trouble; the RSPB’s latest State of Nature report showed that two-fifths of UK species are in decline. Focussing specifically on our feathered friends, in just the last 50 years 40 million birds have vanished from British skies (RSPB, 2021). Some stark evidence of this came from 2021’s Big Garden Birdwatch, a citizen science project organised by the RSPB to paint a picture of how garden birds are faring. Big Garden Birdwatch 2021 had over one million participants, who recorded over 17 million birds. The trends in Big Garden Birdwatch data are analysed to pick out patterns in bird numbers. This year’s count revealed that finch numbers have continued their decline of the last two decades, with chaffinch and greenfinches recording their lowest ever numbers ever (RSPB, 2021) (Finches Friend, 2020). Using data to recognise a pattern is the first stage of the battle, but you then also need know why those trends are occurring, and how to slow or solve them.
Dirty bird feeders are contributing to the drastic decline in greenfinch numbers
Trichomonosis
Trichomonas gallinae is a parasitic disease that affects bird's digestive system (RSPB, 2020) (Lawson, et al., 2011). Trichomonas gallinae typically affects finches, and doves and pigeons. However, any bird can catch the infection (RSPB, 2020). The disease is known as ‘canker’ when it is seen in pigeons and doves, and as ‘frounce’ when seen in birds of prey (British Trust for Ornithology, 2020).
Finch trichomonosis emerged in Britain in 2005 and led to a significant decline in numbers of greenfinches, Carduelis chloris and chaffinches, Fringilla coelebs (Lawson, et al., 2011) (Lawson, et al., 2012). Since the emergence of finch trichomonosis, the breeding greenfinch population in the UK has declined from around 4.3 million to just 2.8 million birds, and the mean average number of greenfinches visiting gardens has declined by 50% (Lawson, et al., 2012). If things don’t change, these species could be extinct in the UK in the next 15 years. Greenfinches and Chaffinches are the species that have been most frequently affected, but trichomonosis has been documented in others such as House Sparrow, Dunnock, Great Tit, and Siskin (British Trust for Ornithology, 2020).
Trichomonosis is often spread from bird to bird via dirty bird feeders (RSPB, 2020). The infection is spread through food and drinking water that is contaminated with droppings, vomit, and regurgitated saliva, as well as when birds feed one another with regurgitated food during the breeding season (RSPB, 2020). We feed birds to take care of them, but we could be inadvertently causing harm through dirty bird feeders.
Since 2005, Trichomonosis has spread throughout England and Wales, and more recently to southern Fennoscandia. Confirmed instances of diseases being spread by migratory birds are very rare, however an international team of experts used epidemiological, molecular, and ringing data to show that the strain of Trichomonosis is identical in all locations. This illustrates that the migration of Chaffinches has been mainly responsible for its spread. This was the first documented case of a protozoal parasitic infection being transmitted in this way (Lawson, et al., 2011).
Greenfinch Carduelis chloris perched on branch showing signs of disease (trichomoniasis)
What can we do?
One fundamental way to fight Trichomonosis is to recognise the symptoms in your garden. Trichomonosis causes lesions in bird’s throats which make it progressively more difficult for the bird to swallow food. Infected birds show general signs of illness such as being lethargic and having fluffed-up plumage, but they may also regurgitate food, have difficulty swallowing, or have laboured breathing. Sometimes it’s possible to see swelling in the throat or to see an infected bird stretch its neck in discomfort. Finches that are suffering from the disease often have wet, matted plumage around their face, and can have uneaten food around the beak (RSPB, 2020).
If you are feeding birds in your garden, is it vital to follow sensible hygiene precautions as a routine measure. A regular cleaning routine is key to stopping the spread of disease, the British Trust for Ornithology recommends that feeders and feeding sites are cleaned and disinfected each week (British Trust for Ornithology, 2020).
Feeders should be cleaned in suitable disinfectants, such as a weak solution of domestic bleach or specially designed commercial products. After cleaning and disinfecting, feeders should be rinsed thoroughly and left to air-dry before being filled again (British Trust for Ornithology, 2020). At Finches Friend, we believe that weekly cleaning is key to combating the spread of the disease among bird populations. We designed Finches Friend Cleaner Feeders especially so that it would be easy and convenient to maintain a regular cleaning routine. As well as regular cleaning, rotating the position of feeders in the garden can prevent the build-up of contaminated material in one area. You should also empty and airdry your bird baths on a regular basis. (British Trust for Ornithology, 2020).
If any of the birds in your garden are showing symptoms of trichomonosis, it is recommended to temporarily stop putting out food and leave bird baths dry until there are no more sick or dead birds seen in the garden (RSPB, 2020). Temporarily stopping feeding will help to slow down the outbreak by forcing the birds to feed elsewhere at a lower density and reducing contact between sick and healthy individuals (British Trust for Ornithology, 2020) (RSPB, 2020).
A regular cleaning routine is key to stopping the spread of disease, the British Trust for Ornithology recommends that feeders and feeding sites are cleaned and disinfected each week
Summary
Feeding birds in your garden is a fantastic way to connect with nature, learn about the world around us, and provide resources for wild bird – so long as it is done safely (Clark, Jones, & Reynolds, 2019). Weekly cleaning and disinfecting of feeders that are quick and convenient to clean, like the Finches Friend Cleaner Feeder which features a replaceable feed station, is key to keeping feeding stations safe and protecting the birds in your garden from diseases like Trichomonosis.
References
British Trust for Ornithology. (2020). Trichomonosis. Retrieved from British Trust for Ornithology: https://www.bto.org/our-science/projects/gbw/gardens-wildlife/garden-birds/disease/trichomonosis
Clark, D. N., Jones, D. N., & Reynolds, S. J. (2019). Exploring the motivations for garden bird feeding in south-east England. Ecology and Society, 24(1).
Davies, Z. G., Fuller, R. A., Dallimer, M., Loram, A., & Gaston, K. J. (2012). Household Factors Influencing Participation in Bird Feeding Activity: A National Scale Analysis. PLOS ONE.
Lawson, B., Robert, R. A., Colvile, K. M., Peck, K. M., Chantrey, J., Pennycott, T. W., . . . Cunningham, A. A. (2012). The emergence and spread of finch trichomonosis in the British Isles. Philosphical Transactions of the Royal Society B, 2852–2863.
Lawson, B., Robinson, R., Neimanis, A., Handeland, K., Isomursu, M., Agren, E., . . . Cunningham, A. (2011). Evidence of Spread of the Emerging Infectious Disease, Finch Trichomonosis, by Migrating birds. Ecohealth Volume, 8, 143–153.
RSPB. (2020). Bird diseases in garden birds. Retrieved from RSPB: https://www.rspb.org.uk/birds-and-wildlife/advice/how-you-can-help-birds/disease-and-garden-wildlife/diseases-in-garden-birds/
RSPB. (2021). Big Garden Birdwatch Results. Retrieved from RSPB: https://www.rspb.org.uk/get-involved/activities/birdwatch/results/
