RENSSEN TA & VOGEL RL (1993) Recent developments of the Raven Corvus corax population in The Netherlands. LIMOSA 66 (3): 107-116.

The Raven became extinct in The Netherlands in the first half of this century, mainly as a result of human persecution. Regular breeding ended in most areas in the course ofthe 1920s. In 1966, a reintroduction project was started that appeared to be successful. Since 1976 the Raven has bred annually on the Veluwe, a large woodand heathland area (1240 km2). After a period of fluctuating low numbers, a marked increase took place from 1984 onwards (fig. 1,2). In 1992, 50 breeding pairs and at least 3I territorial pairs were found, most of them on the Veluwe. Here, the species occurs in 65 % of the 5x 5 km squares. The spacing of territories is rather regular on the Veluwe, but highest densities occur in the central part of the area. Almost all breeding pairs are located in old pine forests Pinus sylvestris near heathland or drift sands. Since 1990 some pairs are breeding in fir-woods Pseudotsuga menziesii, damaged by gales. Breeding success is slightly lower than elsewhere in Europe, 2. I young reared per breeding pair (calculated for pairs that started egglaying only). It is expected that the Dutch breeding area will expand in the next decades, and that Dutch and German populations will interchange before the year 2000 (fig. 3). Territorial Ravens probably stay within their territories during the whole year. Non-breeders often birds occur in wandering groups. Non-breeding birds have been studied systematically since 1989. About 95% of all observations were made on the Veluwe (fig. 4). Since the winter of 1986/87 flocks of 30-50 non-breeding birds are found here each winter. Groups of 6-8 non-breeding birds are observed in the woodland area of the Utrechtse Heuvelrug (240 km2) since spring 1992. Despite the strong increase, Ravens are seldom seen in agricultural areas. The size and dispersion of the flocks of non-breeding birds on the Veluwe probably depend~on the abundance of food. In early spring, flocks of up- to 30 birds are regularly observed on heathland in the SE-Veluwe, often in the vicinity of sheep and feeding on still-born lambs and afterbirths (in this, they differ from the breeding birds that stay in pine forests and heathland in early spring, foraging on carrion and beetle-larvae, taken by slashing at putrefied trees). In April and May non-territorial Ravens occur all-over the Veluwe in flocks of 5-15 birds (up to 42 birds). Important food sources in late spring and summer are probably invertebrates, garbage left by tourists and carrion including animals killed by traffic. In autumn and winter up to 50 Ravens may occur nearfeeding places of wild boar and red deer, foraging on entrails left after hunting. In the course of winter the main groups seem to move from the northeast to the southeast of the Veluwe (fig. 5). In February, groups of 50 Ravens have been observed. In winter 1990/91 a roost (max. 38 birds) was studied on the SE-Veluwe in coniferous woodland, close to major feeding-grounds. Highest numbers were present in February (figure 6). Small roosts are likely to occur elsewhere on the Veluwe as well. In autumn 1992, the Dutch population was estimated at 400-475 individuals, about 95% of which on the Veluwe. Common Raven Corvus corax

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