Thursday, 12 January 2006

Pigeons feast on ivy berries

The end wall of my garden is hidden beneath a mass of ivy. Arising from a single trunk, whose girth far exceeds that of my thigh, the ivy has spread nearly thirty feet, bushing up and out along the wall. Over recent weeks the ivy has become the favoured dining location for the local woodpigeons, which have come to feast on the unripe berries. The antics of these birds are a delight to watch and I have been surprised by their agility. Individuals clamber about among the foliage, sometimes bracing themselves with half-open wings and stretching head down to reach more distant fruits. They rarely seem to over-balance but do, on occasion, appear less than dignified in their posture.

A hungry woodpigeon will fill its crop with a very large meal, eating up to 450 berries in a sitting, and will follow this with a long period of rest and digestion. Individuals that have had their fill loaf about in the tall trees beyond the end of the garden, sitting high and alert to occasional forays by the local sparrowhawk. It is during late winter that woodpigeons typically turn to ivy. The berries are nutritious and have an especially high fat content. Interestingly, when ripe, they are known to be moderately poisonous to mammals and at least some birds, if eaten in any quantity. It is not clear if the woodpigeon is immune to the toxins or whether it is able to deal with them by being particularly careful in how it treats the fruit once eaten. Perhaps the berries contain fewer toxins when unripe. The berries are an important stopgap, a food that is available at a time when other favoured foods have become scarce. Certainly, the pigeons seem to move onto ivy berries earlier in years when the autumn beechmast crop has been poor. 

Ivy is not the only winter food that woodpigeons have learnt to utilise. They have also taken to oil seed rape in a big way and the introduction of this crop has made a big difference to our woodpigeon population. Historically, under farming regimes with over-winter stubbles followed by the spring sowing of cereals, the lack of suitable food between January and March was known to be the controlling factor behind woodpigeon population change. Many woodpigeons would starve during this period and the population would be kept in check. With the introduction of this new crop, the brake halting population growth has been removed allowing our woodpigeon population to expand in the manner that it has over the last ten years. This may be one of the reasons why so many woodpigeons seem to descend on my garden at this time of the year.

No comments:

Post a Comment