Songbirds are helping trees pollinate in early spring

We’ve all grown up acknowledging that bees and many other insects play a vital role in pollinating plants, so much so that the plight of bees has been linked with our ability to grow sufficient food to feed ourselves. These facts are not in dispute, but what has more recently come to light is the important role that songbirds play in pollinating trees.

Research work carried out at Wicken Fen by researchers from Waipapa Taumata Rau, the University of Auckland and the University of Cambridge found pollen on 89% of the birds studied. Species included Blue tits and Blackcaps, both of which would seem to have helped spring-flowering trees.

The research paper published in the Journal of Ecology detailed how many of the common songbirds on the National Trust’s  800 ha Cambridgeshire site carried pollen, a fact that challenges earlier assumptions. In all, 29 species were sampled, of which nine were found to have regularly transported pollen, sometimes in significant quantities.  All of the birds were caught during regular ringing sessions by the Wicken Fen Ringing Group at three scrub woodland sites on the Fen.

The nine species found to be regular pollen carriers were Blue tit, Blackcap, Chiffchaff, Wren, Redpoll, Bullfinch, Whitethroat, Garden warbler and Willow warbler.

When it comes to tree species, it would seem that pollen from early-flowering trees and shrubs, in particular Goat Willow, Blackthorn, Hawthorn, and Buckthorn, was most often found on the tested birds.

April also seemed to be the peak time for pollen to be carried, most likely due to our notoriously fickle weather, which often remained far too cold or unsettled for ectothermic (cold-blooded) insects to reliably fly. This is when many spring migrants were passing through. With temperatures being lower in April, the amount of pollen being carried by insects like bumblebees would be reduced, so it’s reasonable to assume that the help provided by the birds is important to the success of the fruiting season.

Both the birds and the trees benefit from this activity, as the nectar provided by the trees can supplement the birds’ diet at a time of year when insect numbers are low.

According to the study, not all songbirds are thought to be pollinators, nor did it conclude that birds replace insects as pollinators. However, it did suggest that the role played by birds has been underestimated in the past.

It is also felt that the interactions between the trees and the birds in this way warrant further study, particularly as climate change is having such a major impact on the timing of bird breeding, plant flowering, and the emergence of prey species such as insects.

So while we are deciding on what the most wildlife-friendly plants are to grow in our gardens to attract and feed the birds, maybe more consideration should be given to which trees to grow? It would seem that some species provide far more than just roosting and nesting sites.

“Unheralded, some of these birds are making a significant contribution,” notes lead author Dr Sandra Anderson of the University of Auckland. “Our study is the first to show that native birds pollinate and contribute to fruit-set in native flowering trees in temperate Europe.”

The study also highlights the amazing synergy between very different parts of the natural world and the interconnectedness of all living things.