Thursday, 4 July 2019

Cultural Evolution and Wood Pigeons

Common wood pigeon, Columba palumbus
I'm sitting in my garden enjoying a beautiful sunny summer day with a light breeze. About ten feet to my right is a tangle of buddleia and ceanothus with a vine and a wisteria twinging up through it, having outgrown their pergola. In the centre of this tangle is a wood pigeon's nest. A couple of wood pigeons are strutting about not six feet from me.

Outside my front door, in a tangle of Clematis montanum and making a right mess of my outside lamp and the ground beneath, is another wood pigeon's nest. The first clutch of young having flown about a week ago, they already seem to be sitting on a second clutch of two eggs. Always two and always one male and one female - a 'pigeon pair'.

According to the British Trust for Ornithology (BTO), wood pigeons, Columba palumbus, are now competing with blue tits and blackbirds for the top spot as Britain's commonest garden bird. Something has changed radically in the behaviour of wood pigeons over the last ten to twenty years.

Having lived in Buckinghamshire and Oxfordshire in three different houses each with good-sized gardens during the last forty years, this is the first time we have had wood pigeons in our garden. Even when I was a keen vegetable gardener with rows of tempting brassicas, we were never troubled by wood pigeons.

I was brought up in Rural North Oxfordshire, as readers of my book, In The Blink of An Eye, will be aware. The only time we saw wood pigeons in our garden was during the very severe winter of 1963 when snow covered the land for three months and starving pigeons came into the garden looking for about the only visible green vegetation - brussels sprouts and kale. Several of these poor creatures fell dead in the garden, reduced to skin and bone.

Wood pigeons in those days were common enough to be classified as an agricultural pest, but they were shy birds of woods and fields. So shy were they that walking into a field would put up a flock of wood pigeons to fly to safety into to nearest trees. To shoot pigeons - they were a tasty addition to the dinner menu for us country folk - you needed a hide and decoys.

The explosion of wood pigeons into town and country gardens is reminiscent of the change that occurred in the related collared dove, Streptopelia decaocto, during the 60s and 70s that sent them hurtling from their homelands in Turkey, to colonise just about every park and garden in Europe. The cause of this explosive radiation is still not clear, just as is the change in habit for wood pigeons.

According to Dr Tim Harrison of the BTO:

The surge of Woodpigeons into gardens over recent years is likely to have been caused by several factors. In the countryside, increased production of oilseed rape has provided fresh ‘greens’ to eat throughout the winter. Their success appears to have spilt over into gardens, where plentiful food and nesting opportunities can be found.

I hesitate to disagree with Dr Harrison, but I don't see how a population explosion would result in a change in wood pigeons' tolerance for humans such as we are seeing. Our wood pigeons will almost walk up to us in the garden, and, where other birds fly away when we open our patio doors, our pigeons merely give us a glance and carry on. Although they haven't ventured into the house yet, they will walk up to the open doors and take a good look inside. One factor in this colonization of gardens could have been the presence of collared doves; either emboldening the wood pigeons or conditioning humans to be more tolerant of them.

Another major change has been the conversion of former vegetable gardens into lawns, decking, patios and flower borders with trees and shrubs, as gardens became more a leisure resource and less a means to feed a family.

What has happened here, I think, is a combination of a population explosion, then a cultural change as the young pigeons don't learn to fly away at the first sight of a human. Their parents don't startle and fly off, so nor do they. Humans are no longer a danger. This is a cultural change that they have inherited from their parents; an evolved change of habit brought on by occupation of a new niche as gardens are turned into flower beds and lawns. A change in human culture in the UK has produced a new niche for wood pigeons to exploit. All that was needed was a change in wood pigeon culture facilitated by the way cultures are inherited from their parents.

A prime example of memetic evolution and one which I personally welcome as beautiful addition to our list of garden visitors.

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