Ardea
Official journal of the Netherlands Ornithologists' Union

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Kluijver H.N. (1951) The population ecology of the Great Tit, Parus m. major L.. ARDEA 39 (1-3): 1-135
From 1912 onward, populations of the Great Tit were studied on the estate Oranje Nassau's Oord (O.N.O.) near Wageningen. In this locality, which includes 129 ha of woodland, nestboxes were inspected once a week in the breeding season. From 1936 onwards the Great Tits breeding and roosting in these boxes were trapped and ringed. The observations were compared with those in other localities. 1. The trapping of roosting Great Tits on winter nights, and also the observations at artificial feeding places in winter, suggest an excess of males over females. 2. When a second brood is raised, the pair that reared the first brood usually stays together, and no change of mate was observed if the original partner proved to be still alive. Changes of mate between one year and the next were more common, but likewise maintenance of the pair appeared to be the rule. Two cases of brother-sister matings were observed. After the young leave the nest, they remain dependent on their parents for another 6-22 days. 3. Many young settle in the vicinity of where they were born. They tend to settle to a greater extent within 200-1,000 m of their birthplace than at a distance of 1,000-2,000 m. Some, and perhaps a large proportion, move farther. Of the young born at O.N.O. (area of 129 ha) 36% is estimated to stay there throughout their life. 4. Many young take up residence in September-December of their first year. Threat display is often observed at territorial boundaries in .autumn, as well as in spring. 5-6. The domicile of each individual, i.e. the area within which it breeds and sleeps, covers 3-4 ha. The domiciles of adjacent individuals overlap. Most Great Tits remain for the rest of their life within the domicile which they chose in their first year. The range of each individual, i.e. the area within which it moves about, either solitarily or with its fledged young, or in winter as a member of a flock, usually covers 30-50 ha (on O.N.O.), but it is often more extended in severe winters. 7. Every autumn a more or less strong migration of Great Tits can be observed in Holland. In certain winters, many Great Tits come from abroad and winter here. Likewise some young birds born in Holland wander to Belgium and the North of France. A (small?) proportion of the older birds also undertake autumn movements. Prob. ably this is commoner in birds which have settled in unfavourable habitats. Some of the emigrant individuals appear to settle down permanently in their new quarters. 8-9. The abundance of nesting sites and the nature of the vegetation are important factors in determining the population density. Great Tits prefer broadleaved deciduous woods to conifers. Attachment to the original domicile is in many cases more powerful than preference for a more favourable habitat. 10-12. Individual consistency seems a more important factor in determining the date of egg laying than are environmental differences in the domicile. Artificial winterfeeding appears to accelerate egg laying only slightly. Older females start egg laying rather earlier on the average than yearlings. 13-14. Two environmental factors regulate the time of breeding in spring, the effect of increasing daylenght (which is constant from year to year) being modified by the warmth-sum. The critical warmth sum is about 320C. The influence of climate on the breeding season is probably direct. Under natural conditions the availability of food evidently has no important influence on the time of laying, the amount available in April being normally sufficient every year. In addition to the long term influence of the warmth-sum, air temperature has an important immediate influence on the start of egg laying. A rise in temperature in April often coincides with a rise in the number of new clutches started four days later. 15-17. A varying proportion of the pairs have second broods. Third broods are very rare. The proportion of individuals raising second broods is higher among older females than yearlings. No correlation was found between the frequency of second broods and the meteorological conditions in May and June. 18. A higher proportion of second broods were observed in coniferous woods than in broadleaved or mixed woods, this difference being due not only to habitat as such but also to a lower population density. In several areas, the percentage of second broods each year appeared to be correlated inversely with population density. In years in which the first broods are started later, second broods are slightly scarcer than in other years. 19-21. Clutch-size varies between 1 and 16 eggs. The average clutch size at O.N.O. declines gradually from 10.3 in the first half of April to 6.0 in July. Some individuals consistently have larger clutches than others. Many females have larger clutches in their second and third years than in their first year of breeding. 22-23. There are marked annual and local differences in average clutch-size, which appear to be due to differences in population density. 24. There is an inverse correlation between population density and fecundity. Probably this is due not to competition for food, but to the effects of increased disturbance by fights and mock-fights in consequence of an innate mutual intolerance of the pairs. 25-28. Of 2,022 clutches at O.N.O. 8.4% were deserted or disturbed before the clutch was completed, and 17.9% during incubation and the nestling period. Low temperature and rainfall cause many losses during the nestling period. Nestling survival seems to be independent of brood size. Nesting success seems to be a little higher in mixed and broadleaved woods than in conifers. Population density has no clear influence on nestling survival. 29. The average production rate at O.N.O. varied between 3.9 and 14.1 young per pair. It is density-dependent because fecundity is density-dependent. 30-31. Young born at the end of the breeding season seem to have a greater tendency to emigrate than those born earlier in the year. A higher proportion of the latter were .later found as breeding birds in the vicinity of their birthplace. 32-33. The mortality rate was estimated at 86.8% for the first year of life and 49% per year in older birds. The mortality rate remains constant after the first year of life. The maximum age is at least 9 years. The annual reduction in the number of ringed birds appeared to be higher in the coniferous than the mixed wood. Apart from a possible difference in mortality, this may be due to more long distance shifts of domicile from the coniferous than the mixed wood. Of the older residents present in December, about 25% die before the following May. Of those present in May, about 32% die before the following December. 34. The annual fluctuations in the breeding population in different localities were sometimes synchronous, due to the effects of favourable or unfavourable weather conditions. Many of the other fluctuations, sometimes large ones, were not synchronous in different localities. 35. The annual fluctuations of the Great Tit population are not closely correlated with those of Blue, Coal and Crested Tits. General factors, such as severe winters, have a similar effect on all the species, but do not seem to be the main factors regulating population dynamics. 36. In anyone place the breeding population of the Great Tit fluctuates violently from one year to the next. The breeding population consists of three components viz. older residents, yearlings born in the locality, and immigrants. For the most part these components fluctuate independently of each other. The number of older residents is each year about 50% of the breeding population of the previous year. The number of yearlings which later settle near where they were born shows a positive correlation with the production rate in years with a low breeding population, but not in years with a high breeding population, as the proportion of yearlings which emigrate or die increases as population density rises. The number of immigrants (i.e. yearlings born elsewhere which arrive and settle down between October and March) seems largely independent of the population density in the area where they settle. The amount of immigration and emigration each year has a marked influence on population density. The adverse influence of a cold winter is less clear than expected. It seems especially great when the density at the start of the winter is high. Several factors, such as a high breeding population and a high production rate in the previous summer, a big immigration and a small emigration in the autumn, and a mild winter, may sometimes coincide, leading to an extremely high breeding population, while if all these factors work in the opposite direction, an extremely low population results. A high breeding population is often found after a low one in the preceding year. This is because, with a low breeding population, the production rate tends to be high and the amount of emigration low. As a result the population curve from year to year tends to be saw toothed in form, a steep rise being followed by a deep fall.


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