DIJK AJ VAN, WEIDE M VAN DER , ZOETEBIER D & PLATE C (2001) Rare and colonial breeding birds in The Netherlands in 1998. LIMOSA 74 (1): 1-16.

In 1998, all colonial and rare breeding birds were counted in The Netherlands as part of the annual breeding bird survey. This paper summarises the results published earlier in the annual report (van Dijk et al. 2000) and highlights the most remarkable species and population changes in 1998. Table 1 lists all species recorded, giving details on the actual numbers counted, the estimated size of the national population and the most recent population estimates recorded before. The 1998 breeding season started after an exceptional mild winter. Both January and February were among the mildest of the 20" century with temperatures reaching 13°C at Christmas and 17°C in February. During the breeding season, fieldwork was hampered by above-average amounts of precipitation. Especially March, April and June were exceptionally wet, which resulted in unexpected favourable breeding conditions tor several species. Moreover, high water tables prevented many fields in river valleys to be mown early in the season.
      Among the species recorded in 1998, Great Bittern, Grey Heron, Grey Wagtail and Common Kingfisher showed signs of a slight recovery since the last two severe winters of 1995/96 and 1996/97. Furthermore, the high water tables enhanced breeding opport unities for Black-necked Grebe (300-320 pairs), Spotted Crake (230-280 territories) and Corn Crake (630-690 territories). Distribution ol the latter species had its strongholds in the NE part of the country. After years of continuous declines (c. 450 in 2000.
     Other species (relatively) thriving in 1998 include Purple Heron (340 pairs), Eurasian Spoonbill (1245), White Stork (330), Redcrested Pochard (95-110), Common Ringed Plover (430-440), Mediterranean Gull (415), Little Gull (8), Sandwich Tern (14600), Arctic Tern (2320), Middle Spotted Woodpecker (7), Common Raven (116) and European Serin (400-450). Obvious increases were also reported lor (Greater) Canada Goose (320-350 pairs) and Barnacle Goose (316), which both seem to adapt weil to the local breeding conditions and often breed successfully. Af ter a short period of declines, Great Cormorant (19700) seems to stabilize at about 20 000 pairs. Stable numbers or only minor changes were also reported lor Western Marsh Harrier (1300), Common Tern (18 000), Eurasian Wryneck (60-100), Sand Martin (17 000) and Red-backed Shrike (225235). Low numbers were found for Kentish Plover (270-280), Ruft (135-185), European Herring Gul! (63500), Black Tern (1000, historical low), Tawny Pipit (35-40) and Common Rosefinch (16 territories). Especially Ruft, and also species like Short-eared Owl (45-50 pairs) have become highly endangered.
     New breeding bird species in 1998 included Cattle Egret (one confirmed, but lailed breeding pair, two probable breeding pairs) and Blyth's Reed Warbier. In the latter case a successful mixed breeding pair of male Blyth's and female Marsh Warbier was documented. Furthermore, territorial Western Bonelli's Warbier (2) and Cetti's Warbier (1) were recorded lor the first time since 1993 and 1994 respectively, although breeding evidence was lacking. A breeding attempt by a pair ol Red Kites (first since 1992) unfortunately lacked detailed documentation. Other intriguing observations, although without any breeding evidence, were those of a territorial European Scops Owl (singing in May-June), Ring Ouzel (April-June) and Collared Flycatcher (28 April-17 May). Following a small influx, 12 possible breeding cases of Two-barred Crossbills were recorded, including nest-building. However, none of these proved to be successful.

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