It is well known that some birds pollinate flowers. These birds are mostly found in tropical and subtropical regions and typically they ‘target’ large, brightly coloured flowers rich in nectar.  Perhaps the best known of these avian pollinators are the hummingbirds, which can hover in the air, whilst feeding on the nectar using their long tongues.

Until recently, not much was known about birds acting as pollinators in more northern latitudes.  However, recently biologists were using mist nets to catch and record the birds present at Wicken Fen (in Cambridgeshire).  This is the  UK's oldest National Trust nature reserve and it is a remnant of the ancient fenland that once covered parts of East Anglia.  Whilst ringing and recording the birds, they also swabbed them for pollen grains.

They found that nearly 90% of the birds were carrying pollen, such as wrens, blue tits, and bullfinches. The pollen they carried often came from four species :

• Goat willow
• Blackthorn
• Hawthorn
• Buckthorn

This raised the question “were these birds acting as pollinators?”  So a simple experiment was devised.  They bagged the flowers of several woody shrubs.  The mesh of the bags was big enough to allow insects to enter but would exclude birds from probing the flowers.  They found that the  quantity of fruit set (berries formed) in the blackthorns, hawthorns and buckthorns was reduced, so it was very likely that the birds were helping pollinate the flowers and therefore contributing to fruit set.

These particular species of shrub flower relatively early in Spring, often when the temperature is below ‘the bumblebee operating temperature’ (circa 13^oC).  Without the activity of the birds, pollination would be reduced as these flowers do not self pollinate.   Though this study was limited to one specific area, it seems probable that a number of our flowers and birds are at least partially dependent on each other.

Full details of this study can be found here : https://besjournals.onlinelibrary.wiley.com/doi/10.1111/1365-2745.70361