Insomniacs … or late bedders … will be familiar with the Shipping Forecasts provided by the BBC on Radio 4 at midnight.45 … when I sometimes hear it … as well as at other times in the course of the day.
And, while I am tucked up in bed listening to the radio, the birds in my neighbourhood don’t need me to open the bedroom window and turn the radio volume up to full blast to give them warning of an ‘increasingly strong southerly or south-westerly air flow’ approaching their territory.
They either know, or are about to know, that this weather event is on its way. Yes, I am saying that birds can forecast the weather; and I am saying that gardeners can do worse than take a look at what birds are doing and how they are behaving to get a pretty good idea of how the weather is going to turn out.
The key lies in the words ‘low pressure.’
Birds can sense extremely small changes in atmospheric pressure, probably by means of a special middle ear receptor called the paratympanic organ (PTO), or the Vitali Organ.
The PTO is located in the middle ear and is mechanoreceptive. (And yes, birds do have ears even though they are seldom visible.)
When the barometric pressure drops, birds experience some discomfort in their middle ear; the faster the pressure falls, the more the discomfort increases – some authorities think it may actually become painful.
And, as every person who has experienced air travel knows, air pressure decreases with altitude at all times, necessitating pressurised cabins for passengers and crew.
Now people are not concerned by smallish reductions in air pressure, so light aircraft … which don’t travel at anything approaching the height of a jet airliner … don’t need to be pressurised.
But birds’ hyper-sensitive PTOs mean that birds are more comfortable closer to the ground when low pressure is dominant and will fly higher when high pressure reigns.
Low atmospheric pressure is usually a precursor of wind and rain. Obviously, birds are not happy in windy or wet conditions and will try to make preparations for limiting the amount of flying they must do if air pressure is falling.
If … unlike me … you are up and about at the crack of dawn and there are birds enthusiastically feeding in your garden, they are ‘getting the food in’ before the weather deteriorates.
If the coming day is going to get off to a fine start, the birds are much more likely to be concerned with their feathers and to be preening, preparing for an active day of flight. And at any time of the day, if you notice that the nearby birds have all gone quiet and have stopped squabbling or calling out, gather in all your precious gardening tools and expect the rain to come on soon. They know, you know.
Not all ornithological authorities subscribe to the PTO theory. Some think that pressure changes are sensed in the air sacs that help fill a good deal of the space inside birds’ bodies. But whatever the mechanism, birds are definitely expert weather forecasters.