WINGING THE WET

This winter’s weather has been extraordinarily wet but the birds in our greenspaces and gardens don’t seem particularly affected. They are flying around quite happily and visiting the feeders whilst we humans have all the palaver of putting on impermeable coats, wellies and hats, and carrying umbrellas.

Rain has a number of impacts on birds, though – it reduces visibility, changes the way air currents behave, wets their feathers altering aerodynamics, and generally causes them to have to make more effort to fly. Wet plumage does not keep the cold out so well, also making the bird heavier which is not desirable for flying. All this also means the birds need more energy, but food may not be so readily available in very wet weather. Larger birds can suffer from hypothermia when they get very wet – smaller species may also suffer but can generally dry out more quickly.

So how has evolution met these challenges? As well as our birds of gardens and countryside, water birds such as ducks, gulls, moorhens and all the other species we see on lakes, rivers, estuaries and the sea don’t sink; they manage to survive and reproduce very well. Ornithologists will know that there are several adaptations which keep birds dry and active in the wet. Perhaps the most important is the uropygial gland, a type of sebaceous gland located dorsally near the base of the tail. This secretes a waterproofing oil and has a little bunch of feathers at its outlet(s) which acts rather like a wick, used by the bird in preening, which action distributes the oil through the plumage as a result of the regular preening process observed in very many birds and highly developed in water birds. It is absent in some avian groups, though, notably flightless terrestrial species such as emus, ostriches and cassowaries. You can find more technical detail in the Encyclopaedia Britannica or on Wikipedia.

The other important adaptation is the structure of birds’ feathers. If you examine a feather closely under a microscope you can see tiny interlocking barbules/papillae which keep the barbs together and maintain the feathers’ structural integrity. This is aided by preening and the action of the uropygial secretions smoothing the plumage to improve aerodynamics and further aid water resistance, as well as improving thermal insulation.

This is a photograph I took of a feather blade under high magnification showing the fine structure and the way the barbules on the barbs interconnect.

Of course, there are behavioural adaptations, too. Birds can avoid turbulent storms, find sheltered roosts, and search for food in places not soaked by the rain where there is more cover.

Betts Ecology help birds by providing areas of shelter in thick hedges and scrub, nest boxes and rich foraging habitats. Please remember that cats are major predators of birds and we ask all cat owners to abide by our pets policy which can be found at https://www.bettsecology.co.uk/policies. Thank you.

 © Betts Ecology