In December, one of our most viewed bird identification guides is for the blackcap, as the species begins arriving in gardens to feed from bird feeders and the berries growing on shrubs.
With its distinctive black cap, the male is fairly easy to identify, but the female with her chestnut brown cap may cause some confusion. A member of the warbler family, blackcaps are known for their rich, melodic song. They are the closest relative of garden warblers, which look quite different but share a similar song and compete for nesting territories in woodland habitats.
During the breeding season, blackcaps primarily feed on insects, spiders, beetles, caterpillars, and occasionally small snails. By late summer, their diet shifts to fruit. They eat a wide variety of small fruits, squeezing out the seeds onto branches before consuming the pulp.
Until the 1950s, sightings of blackcaps wintering in Britain were rare. Most would migrate south to Germany and northeast Europe to find food as UK berry supplies dwindled. However, with the rise of garden bird feeders and milder winters due to climate change, more blackcaps are now staying in Britain during winter, with up to 3,000 recorded annually.
Blackcaps are adaptable feeders in winter, happily eating kitchen scraps such as bread, fruit, and suet, which make up about 20% of their diet. They’ve also learned to take peanuts and husk-free seeds from feeders, defending their food sources aggressively from starlings and blackbirds. They also enjoy berries from shrubs such as cotoneaster, ivy, and honeysuckle, as well as windfall apples.
While all this activity is happening in gardens, things in the countryside have been winding down, and now that deciduous trees have shed their leaves, large, spherical balls of mistletoe (Viscum album) are visible growing at the tops of the bare branches.
Mistletoe, also known as European mistletoe or common mistletoe, is a type of hemiparasitic evergreen plant that grows on the branches or trunks of trees and shrubs. It is native to Europe, western and southern Asia, and has been introduced to North Africa, although it is rare in this region. It has thick, leathery leaves, and its waxy berries are white or pale yellow.
Mistletoe attaches to its host tree using specialised structures called haustoria, which penetrate the bark and tissues to draw water and nutrients. As it can photosynthesize independently, mistletoe is considered a hemiparasitic plant, rather than a holoparasitic one, which relies entirely on its host for food and carbon. Common trees that host mistletoe include apple, oak, hawthorn, poplar, and lime.
Contrary to popular belief, mistletoe is unlikely to harm a tree unless it is very weak or young, and it can coexist with its hosts for decades. Mistletoe also plays an important ecological role, supporting wildlife by providing food for various insects, such as the mistletoe marble moth (Celypha woodiana) and the mistletoe weevil (Ixapion variegatum), as well as a range of bird species.
The most well-known bird that feeds on mistletoe is the mistle thrush (Turdus viscivorus), which gets its name from the plant. The English name “mistle” is derived from an old word for the plant, and the scientific name viscivorus comes from the Latin viscum (meaning “mistletoe”) and vorare (meaning “to devour”), reflecting its diet.
The mistle thrush is an important propagator of mistletoe. It consumes the berries, digesting the flesh while the sticky seeds pass through its digestive system, which are then excreted and deposited on suitable branches for germination. Fieldfares and redwings also eat mistletoe, dispersing the seeds in the same manner.
