’25 years of garden birdwatch’, a talk by David White of the BTO
David is one of the BTO Garden BirdWatch team. He said that the project was launched in 1995 and participants record the maximum number of each species of bird and optionally, mammals, reptiles, amphibians, butterflies, dragonflies and other selected invertebrates, seen in the garden each week. It is very similar to the RSPB’s January Big Garden Birdwatch which started in 1979. Data from both schemes are important because they show trends in garden birds. For example, woodpigeon and goldfinch have increased while house sparrow, starling, greenfinch, wren and song thrush have decreased.
The song thrush has dropped 8 places but other surveys show that it is doing quite well in the countryside. It may experience competition from other garden birds. The greenfinch, which is down 7 places, has declined as a result of the disease, trichomonosis. On the plus side, nuthatch has moved up 6 places reflecting its range expansion, particularly northwards. Woodpigeons have adapted well to gardens and moved up 10 places. They are opportunists and can eat a good amount at one sitting so are not always popular! However it is the goldfinch which has shown the most change, moving up 12 places probably attracted by householders providing niger seeds and sunflower hearts.
The collared dove first nested in the UK in 1955 having spread across mainland Europe. Numbers are currently decreasing, probably as a result of trichomonosis. A more recent addition is the ring-necked parakeet. No one knows how it was introduced but it is able to withstand British winters. While the bulk of the population is still in the London area it is spreading. At present there is no evidence that it is outcompeting native hole-nesting species.
The reed bunting is primarily a wetland species but also frequents farmland. By late winter seed is becoming scarce and this is when some move to gardens. The blackcap used to be a summer visitor only but now there is a wintering population often visiting gardens. BTO research using geolocators and colour rings shows that these birds breed over a wide area stretching from Poland to Northern Spain so a milder climate cannot be the sole attraction and the supply of food in garden feeders is thought to play a part. Gardens of whatever size offer a home to wildlife. All contain some natural food but if feeders are put out more species will visit.
David said that the 2019 BTO/ Springwatch/ Open University Gardenwatch project produced the biggest ever garden audit. Some highlights are:
42% of participants had a leaf pile which is beneficial to grass snakes and some insects;
30% left some grass to grow long benefitting invertebrates and species like blackbird;
19% helped hedgehogs by providing homes, making gaps in fences for access or providing food such as cat-food – not mealworms or milk;
House sparrows were very reliant on human buildings for nest sites and doing well in the southwest;
Robins were also doing well here;
Chaffinches were visiting more garden feeders in Scotland than in England.
Garden BirdWatch collects information on beak deformities. These have included a blackbird with a short upper mandible (keratin deficiency), a starling with an exceptionally long beak which appeared to be coping successfully and a rook with a crossed mandible which was likely to hamper its ability to feed. A survey of abnormal plumage showed that this was most likely to occur in blackbirds, house sparrows, jackdaws and crows but a completely white dunnock was reported.
Sick, injured or dead birds are recorded and the Garden Wildlife Health Project helps to track disease outbreaks. Greenfinches are particularly susceptible to trichomonosis which is spread round feeders and birdbaths by their saliva and has resulted in a population decrease. David emphasised the importance of cleaning and disinfecting feeders at least fortnightly. Feeding should be stopped for two weeks if sick birds are seen. Chaffinches are subject to fringilla papillomavirus, a growth on the feet and legs. Great tits are particularly susceptible to avian pox which produces tumour-like growths and is caused by insect bites.
Many Garden BirdWatchers took part in the 2018/19 Tawny Owl Calling Survey which showed they were most vocal from October to December on warm clear nights. Both sexes call “tu-whit” but only the male calls “tu-whoo”.
David mentioned one or two recent butterfly highlights from Garden BirdWatch. Holly blue normally peak in April but last year the peak came in February. This puts them at risk if there is a cold snap later. The migrant painted lady usually peaks every 10 years or so, most recently in 2009 and 2019. In August 2019 there were 30% more than usual but this August counts were very low.
Finally David reminded us that anyone can sign up for Garden BirdWatch on the BTO website and it is free.
We thank David for a very interesting and enjoyable talk about the survey which is providing so much valuable data about our garden birds and other wildlife. I can personally recommend taking part.
Helen Baker
