Where have all the greenfinches gone?

When did you last see a greenfinch in Hastings? Probably a while ago – sightings are getting rarer as the population is in serious decline. David Campbell, bird recorder for the Sussex Ornithological Society, said, “Ten years ago we saw greenfinches much more often, but now the numbers have declined by 65% in the south-east.” As climate change causes the Earth to heat up bird diseases will occur more frequently. This article describes how a parasitic bird disease, Trichomonosis and a virus, bird flu, has affected bird species. Richard Price reports.

The greenfinch is a small bird of the finch family with a chunky flesh-coloured bill and forked tail. Its plumage consists mainly of green. The males are olive green with a yellow-edge to the primary feathers on the edges of their wings and base of the tail. Juveniles are browner and have a mottled back. Greenfinches are a beautiful sight and are pleasant to listen to. The song is a series of jupp sounds finished off with a trill. Their diet consists of seeds, berries, nuts and insects.

Greenfinches were once a common sight almost everywhere in the country. Their range has contracted due to intensive agriculture. And recently populations have plummeted because of the disease trichomonosis, which has also been found in chaffinches, house sparrows, dunnocks, siskins and great tits. The disease is caused by the protozoan parasite Trichomonas gallinae. This has always affected caged birds, but has now become common in wild birds. Its effects became prominent in the summer of 2005 when British finches were found to be declining rapidly as a result of it. Other epidemics occurred in 2006 and 2007 and have followed every year since then.

Trichomonosis is spread through contaminated food and drinking water and when the adults regurgitate food to feed young chicks or fledgelings.

The Royal Society for the Protection of Birds (RSPB) organise an annual event, the Big Garden Birdwatch (BGB). Participants list the number of garden birds that land in their gardens during an hour and submit the records online. The data has proved to be invaluable; scientists use it to gain access to the state of the UK’s birds.

Another initiative is the Garden Wildlife Health (GWH), a partnership between the RSPB, the Zoological Society of London (ZSL), the British Trust for Ornithology (BTO) and Froglife, which is funded by the Esmée Fairbairn Foundation and the Department for Food, Environment and Rural Affairs, Defra. Researchers for the BTO and others involved in GWH use data from BGB to establish the impact of disease on bird populations.

From green to red

UK birds are assessed by scientists who place them into one of three categories of conservation importance: Green, Amber or Red. 2021 data showed greenfinches to be rapidly declining, as a consequence of which the bird jumped straight from the Green List (the least critical group of species) to the Red List (species needing urgent action) – usually birds transition through Amber on their route to Red. The population of greenfinches has crashed due mainly to a severe outbreak of trichomonosis.

Trichomonosis is just one of a number of diseases whose effects and range are likely to increase as increased global temperatures and heats the Earth. A 2008 report by the Wildlife Conservation Society was the basis of a Scientific American article which lists 12 deadly illnesses that global warming may exacerbate. Avian influenza or bird flu (H5N1) also features prominently in the report.

The author, David Biello, wrote: “H5N1 infections are becoming the rule rather than the exception in farmed poultry worldwide, and even wild birds are showing signs of infection more often. It has forced the culling of millions of ducks, chickens and geese globally—and has killed more than 240 people—resulting in at least $100bn in economic losses.” Climate change causes migratory birds to alter their routes and make contact with species they would not have encountered, thus creating new disease vectors.

The Spanish flu was caused by an H1N1 virus that started in a species of bird. The 1918 pandemic infected an estimated 33% of the world’s population, killing about 50m people. Bird flu is causing increasing concern across the world as scientists prepare for the possible occurrence of the next human influenza pandemic.

The Animal and Plant Health Agency (APHA) have an interactive disease map that shows control zones, though none in our corner of the South East. Currently, there are about 60 within which bird keepers have to keep their birds indoors, away from wild birds, and follow biosecurity advice.

In Whitby the Wildlife Sanctuary found a group of cockerels left outside the door of their centre. They decided to treat them but they died soon after arrival and then tested positive for bird flu. The APHA euthanised all birds in the isolation unit whether infected or not.

Mallydams Wood Wildlife Rehabilitation Centre in Fairlight have a note on their Facebook site that states that in line with current government guidance they cannot accept birds.

Super spreaders

In both America and the UK, animal welfare groups have criticised modern poultry farms. The three main criticisms are that poultry are bred for fast growth, causing suffering and pain along with organ failures, while living conditions are crowded, with tens of thousands of birds crammed into industrial incubators. Additionally, the way that they are slaughtered – shackled upside down by the legs and still alive – is considered cruel. The first two criticisms create perfect conditions for the spread of disease.

Thousands of birds in the UK have recently died or been killed because of an ongoing bird flu outbreak.  On 14 January the Independent reported that the Open Cages animal welfare charity had filmed a farm dumping thousands of chickens into open air skips. The charity said that bad biosecurity and animal husbandry were the reasons that we now have annual outbreaks. Bird viruses can be present in air samples up to 110 metres from infected farms.

The outbreak is unprecedented and is severely affecting migratory birds. Ten per cent of the global population of barnacle geese recently died in the Solway Firth, prompting the RSPB to call for an emergency moratorium on shooting geese in the Solway. When birds flee from hunters it costs them valuable energy and causes them to move to new areas and mix with uninfected birds. Should wildfowl hunting continue in the Solway when the global population has just dropped 10% due to birds dying there? Scottish government ministers didn’t see it that way, they immediately rejected the idea of a ban.

People can help slow the spread of bird flu by cleaning their bird feeders once a week or when they change the seed; or temporarily stopping the provision of food if ill birds are seen. During an outbreak garden bird feeders should be cleaned regularly and water changed daily.

The RSPB have advised people to keep their pets away if dead birds are found and not to touch any dead or diseased birds – but do report them.

Sick or diseased birds can be reported using the Garden Wildlife Health (GWH) website. Or, if they are gulls or wildfowl, please call the Defra Helpline (03459 33 55 77).

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