Ardea
Official journal of the Netherlands Ornithologists' Union

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Murton R.K. & Isaacson A.J. (1964) Productivity and egg predation in the Woodpigeon. ARDEA 52 (1-2): 30-47
This paper relates the breeding success and productivity of Woodpigeons to their population density in two different localities in Britain. In the first (Carlton wood) avian predators (Jays and Magpies) were undisturbed in three out of four years of study. At the second locality (Spikehall), studied for two years, predators were extremely rare, the result of intensive control measures by the local gamekeeper. At Carlton, 40% of all the eggs laid were predated compared with only 23% at Spikehall. The success of nestlings was determined by the food supply and because this did not differ between the two sites, the percentage of nestlings fledged was the same in each and was approximately the same in different years. The hatching success of eggs was much lower at Carlton early in the breeding season (May-July) than at Spikehall because of predation, but was similar during the main season. This was because desertion was also important at Spikehall, where an exceptionally high breeding density was recorded. At Carlton, proportionately more eggs were predated with an increase in breeding density. But more eggs were laid with a high predation rate and some of the repeat clutches were successfully hatched. Consequently, the number of young produced per pair was only slightly influenced (statistically not significant) by considerable variations in predation rate and hatching success at different densities. Juvenile mortality was measured during the month following the end of the breeding season. Losses, probably also caused by emigration, were unrelated to population size or to variations in fecundity caused by predation. Juvenile losses were so high after the breeding season (an average of 52% of the young vanished in their first month of life) that differences in fecundity of the scale observed during the present study would be of no value in ensuring any control of population size. Some further evidence is advanced to show that mortality between breeding seasons is more important in regulating population size.


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