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Résumé :
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[(1) A wood-pigeon (Columba palumbus) population and its clover and grain food supply was censused from 1958 until 1970. During the first six years, winter battue shoots were held between late January until early March and large numbers of birds were killed as they returned to roost. No shooting occurred during the next three years and then an intensive experimental programme of decoy shooting by one man was monitored throughout the last three years. (2) Shooting did not increase the total amount of winter mortality above the level experienced in the absence of shooting. The number of wood-pigeons in autumn and winter was determined by the amount of grain on cereal stubbles, or clover on leys and pastures, respectively, and immigrants moved in to take advantage of any unexploited food resource. (3) There was no increase in pigeon numbers following abolition of battue shoots in 1965. Ringing records show that a higher proportion of recovered pigeons were found dead instead of being shot, suggesting that birds which previously were shot before dying of food shortage now succumbed for natural causes. (4) In 1968-69 the average cost in terms of man-hours and cartridges for an expert decoy gunner to kill one pigeon was [pound]0.24. It cost [pound]0.13 to kill a pigeon with stupefying baits (0.10 man-hours/bird instead of 0.23 man-hours for shooting). For shooting to affect population size, a cost of about [pound]0.50/bird would probably be realistic, assuming sufficient guns were available. (5) For a given number of dead pigeon-decoys the percentage of passing pigeons at risk which responded, decreased as flock size increased as did the percentage shot. Ignoring any scaring benefit, decoy shooting is most effective as a means of killing pigeons when single birds or small flocks are at risk. An increase in the number of dead pigeon decoys with closed wings, to about eighty or, with open wings to about forty, led to an increase in the percentage response from live birds and hence numbers shot, but with more decoys pigeons were repelled. Within the ranges defined (0-80 and 0-40) there was no difference in the effectiveness of dead pigeons with closed or open wings. It is estimated that 7% of live pigeons at risk are killed with five closed-wing decoys, 14% with twenty such decoys and 23% (the maximum) with eighty decoys. Artificial decoys were 13-46% less useful than dead pigeons depending on the number used. (6) A comparison is made of the age and weight distribution of shot wood-pigeons with those captured by the use of stupefying baits and differences are discussed. Variations in the seasonal pattern of shooting mortality consequent on changes in official policy and bounty incentives are examined by an analysis of those recoveries of ringed birds which had been shot.]
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