HULSCHER JB, JONG, J, DE & KLINKEN J VAN (1993) Exceptionally high numbers of inland Oystercatchers during the winter of 1992 - 1993. LIMOSA 66 (3): 117-123.

In the winter of 1992/93 unusually large numbers of Oystercatchers were seen on many inland locations in Friesland and Groningen, the two Dutch provinces that border the Wadden Sea. The available feeding time in the Wadden Sea during low tide was shorter than the time required to match the daily food requirements, due to strong winds resulting in raised waterlevels in November and the first half of December 1992, and again in January 1993. The birds were forced to make up for their supply deficiencies with terrestial food, foraging on inland areas nearby. Inland feeding was probably facilitated by above average precipitation and relatively high temperatures, both raising the availability of earthworms, the main prey species taken. The long-lasting spells with abnormally high temperatures in November may have triggered an early return to the breeding areas in at least some of the birds. Excessive commercial fishing effort has reduced the abundance of cockles and mussels, usually the staple food of Oystercatchers in the Wadden Sea in winter, during the last three years. Consequently, the winter population of Oystercatchers in the Wadden Sea has decreased. Birds that remained to winter in the Wadden Sea have probably switched to other types of prey, with smaller size and occurring in lower densities. Presently the birds need more time to collect the same amount of food than in times when they mainly feed on cockles and mussels. Generally, the birds get in trouble when strong winds prevent sufficiently long exposure of the Wadden Sea feeding areas, because the inland feeding conditions are not suitable in regular winters. In the mild winter of 1992/93 Oystercatchers were lucky. Eurasian Oystercatcher Haematopus ostralegus

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