HUSTINGS F, FOPPEN R, BEEMSTER N, CASTELIJNS H, GROOT H, MEIJER R & STRUCKER B (1995) Spectacular recovery of Dutch breeding population of Bluethroat Luscinia svecica cyanecula. LIMOSA 68 (4): 147-158.

In this paper a reconstruction is presented of changes in breeding numbers and distribution of the Bluethroat in The Netherlands. Within a few decades, a marked increase in breeding numbers (Fig. 1) and a remarkable shift in distribution (Figs. 2,3) have occurred. In the first half of the century the species' stronghold was situated in the eastern and southern parts of the country. By 1950 large parts of its fonner distribution area here had been abandoned as a result of habitat destruction. In the remaining breeding areas a general decrease was noted due to ongoing unfavourable agricultural practices (cultivation, lowering of water tables etc.), leading to a low population level in the 1970s and early 1980s. From the mid 1980s onwards, a strong increase has been recorded. In some areas, however, the species was still rare in the early 1990s. About the same development was recorded in the river area, where a long-tenn decrease was followed by an increase, starting in western parts in the mid 1980s and in eastern parts in the early 1990s. In the northern parts of The Netherlands the species was locally abundant in the first half of the century, but disappeared almost completely afterwards. Recolonisation of this region started in the early 1980s. In the western parts of the country, where Bluethroats had always been rather rare, a marked increase took place in the 1980s. In the SW of the country breeding was formerly restricted to parts of Zealand Flanders. Here, a strong increase started in the mid 1970s, and areas outside Zealand Flanders were colonised in the 1980s. The most spectacular increase took place in Zuidelijk Flevoland and the Biesbosch. In F1evoland, a polder reclaimed (1968) in Lake IJsselmeer, large numbers occurred in arable habitat (first years of cultivation), young plantations and marshland. Despite intensified land use and cultivation of most marshes, numbers have remained at high levels due to an increase in the largest marshland here, the Oostvaardersplassen. In the Biesbosch, the exclusion of the tide (1970) was followed by an explosion of Bluethroat numbers. After peak numbers around 1987, the local population has declined slightly. Due to the increase in most parts of the country, the Dutch breeding population has grown from less than 800 pairs in 1970 to about 6500 in 1990, about 50% of which in Flevoland and the Biesbosch (Fig. 4). Habitats occupied by Bluethroats in The Netherlands include overgrown marshes (Flevoland, Biesbosch, river area), peat bogs and brooks (eastern and southern parts of country), arable land with rapeseed and other crops intersected with ditches (northern parts, Flevoland), creeks (Zealand-Flanders) and osierbeds (river area). Recently, habitat preference seems to broaden in some areas, as e.g. artificial lakes in the dunes are occupied. In some areas adjacent to Flevoland and the Biesbosch, the expansion of the Bluethroat may have been caused by dispersal from these 'source' areas. It seems unlikely, however, that the increase in for instance Zealand Flanders or the southern part of the country (two areas where the species had always been present) was exclusively caused by immigration from these areas. Considering the timing of the increase, for instance, it is more likely that local factors (more favourable habitat management) or overall factors (improved breeding success or winter survival?) were involved as well. Fig. 5 shows how the expansion in The Netherlands may have evolved, starting from several source areas. Bluethroat Luscinia svecica = Cyalnosylvia svecica

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