CAMPHUYSEN CJ (1998) Razorbills Alca torda in Dutch waters. LIMOSA 71 (2): 69-77.

The status of the Razorbill in The Netherlands is conventionally described as are known as "passage migrant and winter visitor (September-April), mainly along the coast." The species has received remarkably little attention in recent Dutch ornithological literature. Results of seawatching add little to the above description, because few passing auks can be specifically identified.
      In this paper the status of the Razorbill in Dutch waters is discussed on the basis of ship-based counts at sea between 1987 and 1997 (50-56°N, 0-8°E; 10,785 km2 surveyed), beached bird surveys since 1969 and particularly since 1977 (34 624 krn surveyed), dissection of 122 stranded birds, and recoveries of birds ringed in breeding areas and beached in The Netherlands between 1935 and 1989.
      Razorbills occur year round in the NW part of the study area (Fig. 1, 2). Small numbers of Razorbill arrive at sea in the ElSE and S in August and September, but numbers rapidly increase in October and November (Fig. 2). The typical winter distribution of Razorbills is shown in Fig. 3, with a wide band of Razorbills off the mainland coast and relatively few birds and an irregular distribution in the Dogger Bank area. A more detailed plot of the observed numbers of Razorbills demonstrates an association of birds with the 20-30m depth contour, with irregularities over sandy bottom (e.g. Brown Bank area, off the Wadden Sea islands) and at the Frisian Front (Fig. 4.). In November and December, nearly all Razorbills were in full winter plumage (Tab. 1). This fraction dropped considerably after January. Peak numbers of Razorbill were recorded in late winter, FebruaryMarch, when an estimated44 000 occurred in Dutch waters (cf c. 160000 Guillemots Uria aalge). Strandings peaked in February (Fig. 2) and overall numbers fluctuated widely between years (Fig. 5).
      An estimated 2650 Razorbills washed ashore in winter 1982/83. Of 2706 Razorbills, 25% were identified as juveniles (black bill), 26% as immatures (bill with white line and up to one groove), the rest as mature birds. The fraction of juveniles varied between 10 and 40% (mean 25%) since the late 1970s (Fig. 5). Remarkably, the proportion of moulting or summer plumage Razorbills did not exceed 5% until April. The difference in the relative abundance of plumage types between birds at sea and beached birds is significant between January and April, suggesting that a non-representative fraction of the population at sea may wash ashore.
      Most ringed Razorbills recovered in The Netherlands originate from British colonies, but singles from Grimsey (Iceland), northern Norway, southern Norway and the White Sea area were found (Fig. 6). Both ring recoveries and biometrics (Tab. 3) suggest that A. t. islandica is the dominant subspecies in Dutch material. The discrepancy between Razorbills at sea and beached Razorbills, as shown by the frequency of plumage types, suggests that analysis of stranded birds alone is misleading when the relative abundance of birds from various populations as winter visitors in Dutch waters is studied.

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