ZIJLSTRA M & HUSTINGS F (1992) Near-disappearance of Montagus Harrier Circus pygargus as a breeding bird in The Netherlands. LIMOSA 65 (1): 7-18.

In the course of the 20th century, the Montagu's Harrier decreased dramatically as a breeding bird in The Netherlands. In the fi.rst half of the century, it was a fairly common and Widespread breeding bird in dunes, heath land moors and marshland (fig. I). Large-scale cultivation of peat moors and heath lands, especially in 1930-50, resulted in considerable habitat loss. The species consequently disappeared from large sections of the country in 1950-77 (fig. Ib, lc), with the exception of a temporal increase in the newly reclaimed polders Zuidelijk and Oost Flevoland (fig. 2). With ongoing habitat loss (cultivation of recently reclaimed polders) and f~rther detenoratmg food supplies, the Montagu's Harner population in this area crashed from 40-50 pairs in 1980 to only a few pairs in 1990 (fig. Id). Population size prior to 1950 is unknown. A minimum number of 180 pairs can be deduced from several sources but given the small number of birdwatchers their uneven distribution and the inaccessibility of main breeding haunts of the Montagu's Harrier, this number must be considered a considerable underestimate. Based on the distribution and size of suitable breeding habitat in 190030 (derived from topographical maps, cf fig. 3), the Dutch population for that episode is estimated at 5001000 pairs (tab. 1). In 1950-90, the population decreased from about 250 .pa~rs to less than 10 pairs (fig. 4). At present, the species IS on the verge of exterpation. The ?ecrease is t?ought to have been caused principly by habitat loss. Pnme habitat, peat moors and heaths, was largely reclaimed during the first part of the 20th century; 460 000 ha (77%) was cultivated and afforested during 1900-90. The remaining heathland has become largely.unsuitable because of habitat fragmentation and recreatIOn: Food availability has also decreased, resulting from detnmental changes in farming practices. These factors alone are thought to have been sufficient to cause the population collapse. In recent decades, large-scaJe spraying of pesticides in some African wintering areas may have added to the negative trend. The .European breeding population, which has strongho~ ds m France and the Iberian Peninsula (fig. 5), is estimated at 7000-9000 pairs (Soviet-Union not inclu~ ed). As .serious declines are reported from most parts of ItS breedmg range, the future for the Montagu's Harrier looks very bleak indeed. Montagu's Harrier Circus pygargus

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