Trills and twitters of finches greet us each morning - at extra volume on the chilly bright mornings - and continue throughout the day as goldfinches, greenfinches and chaffinches compete for space on our bird feeders. Flocks of blue, great and long-tailed tits forage in the tree tops and hedgerows, and occasionally join the finches for seeds or fat balls while our resident blackbirds, robins, wrens and dunnocks can be heard amongst the shrubs and leaf litter.

A robin singing through a tangle of hawthorn

© Jonathan Jackson

Over-wintering redwings were spotted swooping down to feed on the remaining holly berries last month. But what about some of our less common winter visitors? Daniel Osborne, has been looking at recent work by the British Trust for Ornithology (BTO)'s outstanding citizen science experiment Garden BirdWatch which unravels a mystery surrounding the blackcap:

"The Blackcap (Sylvia atricapilla), like other UK warblers, is primarily a summer visitor, arriving in April and May to establish a breeding territory, build a nest and raise young, then departing in September and October to overwinter in Southern Europe and North Africa. Its beautiful varied song can be heard occasionally in the Wildlife Garden in spring and summer and the bird itself - a fairly drab yet distinctive grey and light brown bird, the male with a black cap, the female a brown cap - is regularly observed among the trees and woodland and even bred in the garden in 2012.

Blackcap (Sylvia atricapilla)

© David Tipling

Since the 1950s, with the increase in use of garden bird feeders, the number of Blackcaps overwintering in the UK has increased dramatically. And in the last 30 years ornithologists have noticed the number of blackcaps in the UK during winter has seemed disproportionately large.

A number of bird ringing programmes in the UK and Europe provided the explanation. Bird ringing is the process of catching a bird, often in a net or while it is still in the nest, and attaching a small ring of metal to one of its legs before releasing it.

Bird-ringing in progress

© BTO

The hope is that the ring will be seen again, either by a keen-eyed birdwatcher or by anyone who should happen to chance upon the bird at close enough range. The ring's unique code means that scientists can be certain of an individual bird's movements. This technique has provided a number of extraordinary insights into bird migration including the large number of overwintering blackcaps.

It was found that while some German blackcaps were migrating south to Southern Europe and North Africa some were migrating to spend winter in the UK. The UK's maritime climate warmed by the Gulf Stream means that winters are milder here than in the continental climate of Germany, and global temperatures are increasing as a result of man-made climate change.

This increase in warmth is likely to mean more food, in the form of insects and berries, available during the winter and fewer sub-zero nights to endure, and has no doubt made the UK in recent years a more attractive winter destination, but surely not as attractive as Southern Europe and North Africa. That is, until the added benefit of the artificial food left out in UK gardens is taken into account.

Blackcap migration routes from Germany

The abundance and reliability of artificial food in our gardens is of course invaluable to our native species, particularly in winter. In the last 30 years or so it has also brought about this change in blackcap migration strategy. Ongoing work by Kate Plummer of the BTO has demonstrated that bird feeding activities have been important in the establishment of the overwintering blackcaps.

The food we put out for birds in winter is tempting indeed and the blackcap population that comes here, instead of heading south, enjoys some distinct advantages. The distance is about a third shorter, which means not only do the UK-wintering birds reduce the costs and perils of migration, but they actually arrive back in Germany first.

This means they can take the prime breeding territories and potentially raise a greater number of healthier young. A fascinating by-product of this is that Germany's UK-wintering population and the southerly-wintering population breed at different times and are now genetically distinct. This winter I have so far seen one female blackcap in the Wildlife Garden, but look forward to seeing more of these beautiful birds, and speculating about how they came to be spending winter in the UK."

A female blackcap

© Edwyn Anderton, Flickr

Thank you Daniel. Last weekend we cleaned and repaired our nest boxes ready for this year's residents.

While some of us are head down searching for first flowers, others are alert to life higher up: Wildlife gardener, Daniel Osborne, who often spots some of the Wildlife Garden's less common sightings shares his winter observations:

“For those prepared to venture out in the cold, observing birds in winter has a charm all its own. While many of the enigmatic summer species will have migrated south, and none of the spring breeding displays or nesting behaviour will be in evidence, birds in winter are no less engaging.

There are still many species around. Blackbirds, robins, finches (including colourful flocks of goldfinches), tits, wrens, dunnocks and many corvids are common in gardens throughout winter. They are more or less non-migratory, but movement within these species does occur - from the colder north, and even from the countryside into cities.

One of our resident robins (Erithacus rubecula)

© Mark Humphries

Some species, such as fieldfares and redwings, are encountered only in winter when they leave their summer breeding grounds in Scandinavia and Siberia. Redwings have been recorded in the Garden this year, as in previous years, and a pair of mistle thrush have chosen to make the Garden their home this winter, as reported in our December post.

Redwing (Turdus iliacus) have been spotted in the Garden during the past month
© Phil Hurst

Due to the scarcity of food, many different species will flock together in winter feeding parties. Excellent viewing opportunities are afforded by the absence of foliage on the deciduous trees.

A great tit (Parus major) in the Wildlife Garden

© Derek Adams

And birds are increasingly willing to visit garden bird feeders.

European greenfinch (Carduelis chloris) and blue tit (Parus caeruleus) on our garden bird feeder

© Derek Adams

Our resident moorhens (Gallinula chloropis) ensure nothing is left to waste below the feeders...

© Derek Adams

... Though some can get left behind.

© Mark Humphries

The feeders in the Garden are usually in regular need of refilling during the winter months, although not too much this winter so far. The relatively mild temperatures appear to be offering a continued availability of natural food, and it is interesting to note that the blackbirds only recently started feeding on the rowan berries that they usually pluck in August with precise bursts of hummingbird-like hovering.

Blackbirds (Turdus merula) feed off rowan berries most summers ... but not last summer

© Derek Adams

Blackbirds are seen frequently at all times of year in the Garden. They are common, and easily identified, the males a uniform black with a bright orange bill and eye, the females a diffuse brown as seen above and further below.

Male blackbird in the Wildlife Garden
© Mark Humphries

They have the habit of cackling noisily when they take off and slowly bringing their tails up to the vertical when they land, making them identifiable even at distance.

Female blackbird
© Derek Adams

The males are territorial and will often proclaim their territory from the same branch. It's my estimate that the Garden is the site of at least three different male blackbird territories. One male has a spot in the apple tree in the orchard area from which he can regularly be heard singing. At this time of year they will be re-establishing their territories and, like all birds, looking for enough food to survive.

Winter is undoubtedly a time of great hardship for birds. Severe or extended cold has disastrous effects on bird numbers. But it can also be a time of unrivaled avian spectacle. Starling murmurations are among the most celebrated natural phenomena and reach a peak during winter, when the birds roost most communally.

Common starling (Sturnus vulgaris) - sadly uncommon in the Wildlife Garden - our last sighting was in 2009

© Tim Munsey

Some parts of Britain entertain huge influxes of swans and geese. Waders and wildfowl flock in huge numbers on the coastlines. And for me, in London, there is always the hope of seeing, in my opinion, the most beautiful of birds, waxwings.”

Thank you Daniel!

A waxwing (Bombycilla garrulus) - one that is definitely on our Garden wish-list!

© Phil Hurst 

We'll be sharing more of our bird sightings with you later in the year

Caroline