Heeft de Grutto Limosa limosa toekomst in Drenthe?
Drentse vogels , Volume 13 - Issue 1 p. 10- 26
In the province of Drenthe (2681 km2), the population of the Black-tailed Godwit declined from 7000 pairs in 1966-67 to 1250 pairs at most in 1998-2000 (Table 1). This decline followed in the wake of successive amelioration projects in farmland, which adversally changed the landscape in the latter half of the 20th century. This pattern has been wellstudied in SW-Drenthe, where Godwits declined by 88% since the late 1960s. Godwits first disappeared from wet heathland; in the mid-1960s the species still occurred there in clusters of >100 pairs. The decline in farmland became evident in the 1970s, first and foremost in valleys of streams and rivers. Although the distribution apparently did not change much, the density ‘thinned’ considerably, eventually leading to disappearance from many formerly densily occupied breeding areas in the 1980s and 1990s (Figs. 1 and 2). This situation was aggravated by the conversion of farmland into nature reserves (in SW-Drenthe c. 1800 ha), where breeding and feeding conditions rapidly deteriorated in response of vegetation succession and declining food stocks (manuring often banned). Even in areas specifically purchased to protect meadow birds like Godwits, the decline was as steep as in regular farmland. By the late 1990s, the major part of the much-depleted Godwit population had become dependent on regular farmland (87-92%), rather than nature reserves. This proportion used to be 52-60% in 1970-94, the rest breeding in nature reserves. An increasing proportion of Godwits is breeding on arable land, involving already 16% by 1999 (only 3% in 1996, as evident from nests found in farmland plots). It shows that management of reserves is often contrary to the interests of meadow birds such as Godwits: botanical interests prevail, decisive protection measures are postponed, reserves are too small or surrounded by hostile landscapes. The present distribution of Black-tailed Godwits mirrors that of Snipes Gallinago gallinago and Redshanks Tringa totanus in the 1970s, a clear indication where Godwits are heading (both species virtually vanished from Drenthe). The decline is mainly caused by changes in farmland and farming practices. Hatching success of Black-tailed Godwits in Drenthe in 1996-99 varied between 47 and 57% (Mayfield-method), with predation as an important cause of failure (46% of all identified failures, others mainly being desertion and farming activities). The actual hatching success may be smaller than 40%, as most pairs nowadays nest in regular farmland (where chances of survival are small). Median hatching dates in 1996-99 varied between 2 and 20 May (Fig. 3), i.e. only 7-10 days before most grasslands are being mowed (Table 2). This highly synchronised and large-scale mowing of grasslands removes the protective cover for chicks and has a negative impact on the availability of food. In many breeding areas where eggs were known to have hatched (partly because of special nest protection measures), very few if any chicks survived following widespread mowing. To save Black-tailed Godwits from disappearing from Drenthe, decisive actions should be taken, among others the creation of large reserves for meadow birds with a fine-tuned and effective management in the interest of meadow birds and a considerable delay in mowing dates in regular farmland surrounding reserves (till late June). Present measures are ineffective, costly and often contra-productive in terms of meadow birds.
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