| Habitat and Ecology: |
Behaviour Razorbills are pursuit divers that propel themselves through the water with their wings. They are capable of diving to 120m depth, but mostly forage nearer the surface. They spend most of their lives at sea, only arriving ashore to reproduce. During the prelaying period, they never spend a night in the nest, and even after the egg is laid, only one parent remains in the nest. Diet They are known to consume krill, amongst other prey. In the Bay of Fundy, Canada, 76% of Razorbill stomachs contained krill (Huettman et al 2005). Foraging range This species has been described as coastal rather than pelagic (Huettman et al 2005), and birds tend to be concentrated within 10 km of the shore (BirdLife International 2000, Huettman et al 2005). At Flamborough Head, UK, maximum densities of birds were observed at under 1 km from the colony and 6 - 28 km away from the colony (BirdLife International 2000). Birds were seen up to 25 km from the Pembrokeshire Islands in 1992, with the highest mean density within 5 km, whereas in June 1990, birds were found up to 45 km away (albeit in low numbers beyond 25km) with the highest densities within 10 km (BirdLife International 2000). At the Isle of May during chick rearing, radio-tracking revealed that 91% of birds foraged at over 10 km from the colony, although transect counts showed a density maximum within 5 km of the colony (Wanless et al. 1998). Another area of high bird density was located 35km away over the Wee Bankie (Wanless et al. 1998). Razorbills breeding at St Kilda foraged at the Whale Rock Bank, 38 km away, although a high proportion of the breeding population appeared to be foraging within 5 km of the island. At North Rona the maximum feeding range was 15 km. Razorbills are probably capable of diving to at least 120 m. Analysis of surveys of distribution at sea indicated that very few were present in waters deeper than 200 m during the breeding season, with the greatest abundance found at depths less than 100 m. At the Isle of May, they foraged preferentially in shallow waters (less than 30 m deep) (Wanless et al. 1998). The same individuals used several widely-separated feeding areas on different days and even on the same day (Wanless et al. 1998). Razorbills occur in high numbers around fronts, as around the Irish Sea Front during autumn. On the Isle of May they were found to be associated with both tidal fronts and the presence of the Clyde front during the early breeding season (BirdLife International 2000). They were also highly concentrated at an offshore bank near St Kilda (Leaper et al. 1988, BirdLife International 2000). In winter in the Bay of Fundy, Canada, they tended to forage within tidal upwelling zones (Huettman et al 2005). A significant proportion of Razorbills breeding in North America spend at least part of the winter in the outer Bay of Fundy and in its coastal zone (i.e. less than 8km offshore) (Huettman et al 2005). It is likely that, in winter, the species gathers in relatively small areas where predictable concentrations of prey occur (Huettman et al 2005).
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Increasing
