How Common Birds Help Pollinate Flowers in Britain

Birds are known for all sorts of things, but pollinating flowers in Britain is not usually counted among them.

For years, the idea was dismissed. Insects were thought to do the pollinating, while birds were regarded as casual visitors to flowers rather than participants in the process.

New research published in the Journal of Ecology presents a different picture.

Some of Britain’s most familiar birds are helping out among the flowers, largely unnoticed.

Birds carry pollen too

Researchers led by scientists at the University of Auckland and the University of Cambridge examined common birds in eastern England.

Their findings challenge a long-held assumption about which animals pollinate plants there.

“Unheralded, some of these birds are making a significant contribution,” said Dr Sandra Anderson.

“Their role has been overlooked but it deserves attention.”

What happened at Wicken Fen

The fieldwork took place at Wicken Fen, a National Trust nature reserve in Cambridgeshire.

The 800-hectare reserve, covering about 1,980 acres of ancient fenland, is rich in birds and flowering shrubs.

Over several spring and summer seasons, local bird ringers caught birds using fine mist nets. Immediately after capture, the researchers swabbed each bird’s beak, head and chin for pollen.

The overall results were striking: 89% of birds sampled during one complete season carried pollen of some kind.

That included at least one bird from each of 29 species. Pollen was present almost throughout the bird community.

Birds that carried the load

The birds did not all play an equal part. Nine species consistently carried substantial pollen loads, and the researchers concentrated on those.

They formed a varied group. UK residents such as the wren, blue tit and bullfinch appeared alongside migrants including the blackcap, chiffchaff, whitethroat, willow warbler, garden warbler and redpoll.

These birds arrive, breed or remain in place at different times of year. Together, they are present throughout the early spring flowering period.

Early bloomers get bird visits

A handful of early-flowering trees and shrubs supplied most of the pollen. Goat willow, blackthorn, hawthorn and buckthorn consistently headed the list.

Their flowers open when conditions are still cold and changeable, a timing that is central to the findings.

Birds’ pollen loads rose sharply to a peak in April, when the average load was several times greater than in any other month.

Why warm blood matters

Cold weather is a serious obstacle for insects. At temperatures below roughly 13°C, or about 55°F, most pollinating insects other than bumblebees remain grounded.

Birds are not subject to the same restriction. Because they are warm-blooded, they continue foraging on chilly mornings when almost no six-legged visitors can fly.

For a plant needing a pollinator during that cool early period, an active, hungry bird may be the most reliable visitor available.

Blocking birds from flowers

Transporting pollen is different from actually helping a plant produce fruit, so the researchers designed an experiment to test the latter.

They covered some flowers with mesh bags that admitted insects but excluded birds.

They then compared the fruit produced by those flowers with that of flowers left accessible to all visitors.

The outcome was clear for the earliest-flowering plants: blackthorn, hawthorn and buckthorn produced noticeably more fruit when birds had access to their flowers.

Plants’ dependence on bird pollination

The strongest effect occurred in plants that cannot fertilise themselves or that bear male and female flowers on separate trees.

Such species depend particularly heavily on visitors to carry pollen between plants.

“Our study is the first to show that native birds pollinate and contribute to fruit-set in native flowering trees in temperate Europe,” says Anderson.

“Understanding this aspect of an ecosystem gives us a better idea of its resilience and how to protect it.”

The matching rule breaks down

Pollination biology has a long-standing rule of thumb: flowers are expected to “match” their pollinators in shape, colour and reward.

Under that reasoning, small, pale flowers are suited to insects, whereas large, conspicuous blooms rich in nectar are suited to birds. The British shrubs studied here fit the insect pattern rather than the bird one.

Nevertheless, birds pollinated them. A successful match appears to depend on much more than a flower’s appearance.

“But the things that determine a match actually vary depending on context; a small pale flower can suit a bird very well if it is accessible and abundant at a time when birds have high needs and there is little else available,” said Anderson.

Birds without the right equipment

Bird pollinators described in textbooks are equipped for the job, typically with long bills and brush-tipped tongues that can reach nectar deep within flowers.

Most of the Wicken Fen birds had no such specialist equipment. They had ordinary bills, and their visits to flowers were often part of a broader search for insects.

Even so, they transferred pollen effectively. Willow and hedgerow flowers presented nectar openly and grew in clusters on sturdy perches, making them easy for any bird to use.

What this means for wild places

These were not rare, demanding specialists, but familiar garden and hedgerow birds carrying out a role almost nobody had recognised.

Anderson first began considering the question after conducting similar research in New Zealand, before bringing it back to Britain.

Her findings suggest that connections between birds and flowers could be much more widespread across Europe than textbooks imply.

The implications extend beyond a single fen: a pollination network with more participants is more robust and better able to hold together as the climate continues to change.

For now, the modest blackcap and blue tit have earned a little extra respect. On cold spring days, they may be helping to keep the countryside in flower.