Our winter visitors to our gardens aren’t all that they seem – for instance around 12% of those familiar blackbirds are immigrants from Eastern Europe or Scandinavia according to research by my friends at BTO.
It is easy to dismiss the Blackbird as just another common, year-round, garden resident. But to do so would overlook some fascinating behaviours. Research, for example, has revealed that at least 12% of the Blackbirds present in Britain and Ireland during the winter are immigrants from elsewhere in Europe and, far from just feeding on fruit and earthworms, Blackbirds have even been observed to take tadpoles and newts from the shallows of garden ponds.
Making the most of gardens
The Blackbird is a species of woodland and woodland edge, but one that has adapted very well to the urban environment. In fact, it is thought that urban Blackbird populations may even act as a source for less productive woodland populations, which face significantly greater levels of nest predation. The most serious threat to urban-nesting Blackbirds is probably prolonged periods of dry weather, which restricts access to earthworms living within parched garden lawns and puts Blackbird chicks at risk of starvation.
Much of our understanding of these urban and suburban Blackbird populations comes from a small number of intensive studies. These demonstrate that traditional breeding territories and feeding sites may be used year after year, particularly by socially dominant individuals. The availability of food throughout the year – Blackbirds are catholic in their dietary tastes – enables the birds to maintain compact, tightly packed territories, sometimes with individuals also using ‘communal’ feeding areas outside of their established territories.
Interestingly, information from the weekly BTO Garden BirdWatch reveals an underlying seasonal pattern of garden use, with a drop in garden use from August through until the end of October. This ‘autumn trough’ is probably linked to the availability of fruits and berries in local hedgerows and more widely to the post-breeding moult – when moulting individuals become rather shy and retiring in their habits.
Night-time singing and early arrivals
The Blackbird is one of a small number of species that sometimes sing during the night, a behaviour that occurs more often in the presence of street-lighting. Blackbirds have large eyes, relative to their body size, and BTO research has revealed them to be the first species to arrive at garden feeding stations on dark winter mornings. Visual capability at low light levels influences when a species is first able to move around and find food.
BTO research has also demonstrated that Blackbirds living within urbanised landscapes arrive at garden feeding stations later than those living in rural gardens. This finding seems to run counter to the influence of light levels on arrival times – since urban areas have more street lights – and suggests that temperature may also play a role. Urban habitats have higher levels of heat pollution, which raises local temperature above that in the surrounding countryside; since small birds have to burn energy reserves to keep warm overnight, you might expect rural birds to expend more of their reserves overnight, this increasing the urgency for finding food in the morning.
The arrival of many thousands of Blackbirds during the autumn months goes largely unnoticed, primarily because they look the same as those birds that are here all year round. However, an early morning visit to some berry-laden coastal scrub and hedgerows will reveal these immigrants, feeding alongside newly arrived Redwing and Fieldfare. The efforts of BTO bird ringers have revealed that our winter immigrants originate in Finland, Sweden and Denmark, with others arriving from the Netherlands and Germany. Some of these birds are only passing through, and will continue south to winter in Spain, France and Portugal.
Windfall apples and berry-laden hedgerows may draw wintering Blackbirds into our gardens, with the numbers using gardens increasing during periods of poor weather. Being able to watch several Blackbirds together should help you to recognise the different plumages, separating the brown females from the black-plumaged males, and young birds (with some juvenile wing feathers still retained) from older individuals. Occasional individuals showing one or more white feathers, may also be noticed in a garden setting. These are birds, most likely, with a plumage abnormality called ‘leucism’ or ‘progressive greying’, both linked to an absence of pigment cells.