Bird pests

A couple of important bird pests are included here.

The wood-pigeon (Columba palumbus)
Damage: This attractive-looking, 40 cm long, blue-grey pigeon with white underwing bars is known to horticulturists as a serious pest on most outdoor edible crops. In spring, seeds and seedlings of crops such as brassicas, beans and germinating turf may be systematically eaten. In summer , cereals and clover receive its attention; in autumn, tree fruits may be taken in large quantities, while in winter, cereals and brassicas are often seriously attacked, the latter when snowfall prevents the consumption of other food. The wood-pigeon is invariably attracted to high protein foods such as seeds when they are available.

Life cycle: Wood-pigeons lay several clutches of two eggs per year from March to September. The August/September clutches show highest survival. The eggs, laid on a nest of twigs situated deep inside the tree, hatch after about 18 days, and the young ones remain in the nest for 20–30 days. Predators such as jays and magpies eat many eggs, but the main population-control factor is the availability of food in winter. Numbers in the British Isles are boosted a little by migrating Scandinavian pigeons in April, but the large majority of this species is resident and non-migratory.

Control: The wood-pigeon spends much of its time feeding on wild plants, and only a small proportion of its time on crops. Control of the whole population, therefore, seems ethically unsound and is both costly and impracticable. Physical control involves the protection of particular fields by means of scaring devices which include scarecrows, bangers (firecrackers or gas guns), artificial hawks on wires, or rotating orange and black vanes, all which disturb the pigeons. Changing the type and location of the device every few days helps prevent the pigeons from becoming indifferent. The use of the shotgun by licenced operators from hidden positions such as hides and ditches (particularly when plastic decoy pigeons are placed in the field) is an important additional method of scaring birds and thus protecting crops.

The bullfinch (Pyrrhula pyrrhula)
This is a strikingly-coloured, 14 cm long bird, characterized by its sturdy appearance and broad bill. The male has a rose-red breast, blue-grey back and black headcap. The female has a less striking pink breast and yellowish-brown back.

Damage: From April to September the bird progressively feeds on seeds of wild plants, e.g. chickweed, buttercup, dock, fat hen and blackberry. From September to April, the species forms small flocks that, in addition to feeding on buds and seeds of wild species, e.g. docks, willow, oak and hawthorn, turn their attention to buds of soft and top fruit. Gooseberries are attacked from November to January, apples from February to April and blackcurrants from March to April. The birds are shy, preferring to forage on the edges of orchards, but as winter advances they become bolder, moving towards the more central trees and bushes. The birds nip buds out at the rate of about 30 per minute, eating the central meristem tissues. Leaf, flower and fruit development may thus be seriously reduced, and since in some plums and gooseberries there is no regeneration of fruiting points, damage may be seen several years after attack.

Life cycle: The bullfinch produces a platform nest of twigs in birch or hazel trees, and between May and September lays two to three clutches of four to five pale blue eggs, with purple-brown streaks. It can thus quickly re-establish numbers reduced by lack of food or human attempts at control. They are mainly resident, only rarely migrating.

Control: Amateur and Professional horticulturists can use fine mesh netting or cotton or synthetic thread draped over trees. Professional horticulturists spray bitter chemicals such as ziram on to shrubs and trees at the time of expected attack to limit bird numbers. Some additional control is achieved by catching birds (usually immature individuals) in specially designed traps, which close when the bird lands on a perch to eat seeds. Trapped birds are then taken to a nonhorticultural location. Trapping may be started as early as September. Large-scale reinvasion by the same birds in the same season is unlikely as they are territorial, rarely moving more than two miles throughout their lives. Bullfinch trapping is permitted only in scheduled areas of wide-scale fruit production, e.g. Kent.