The behaviour and dispersal of the guillemot (Uria aalge) and razorbill (Alca torda) on the sea at Lundy
Cayford, J. (1981) University of Exeter [Thesis?]
The number of Razorbills and Guillemots in attendance at a small mixed colony on Lundy have been analysed. The spatial niche separation on land is not in evidence on the water. The two species readily associate during the pre-breeding season period and mixed-species groups account for 70%+ of all those groups recorded. The pre-breeding season attendance of both species is remarkably similar with the behaviour of one species re-inforcing the other. An analysis of bird groupings reveals that despite substantial increases in the number of birds in the Cove, the daily mean size of each group category remains constant. The establishment of pair-bonds seems to be an important factor in the way in which birds group themselves during the pre-breeding season period, as is the number of birds in attendance. As the number or Razorbills present in the sampling area increases, so a greater proportion will form a single-species group. Thus mixed-species groups may be important as location centres for small numbers of birds of the same species, for the purpose of pairing. During the breeding season the majority of Razorbills breeding in Jenny's Cove do not associate with each other, or Guillemots within the Cove itself. The massings of Razorbills on the water occurred at two specific times of day for the sole purpose of feeding. During these feeding sessions which show strong correlation with tidal movements, small numbers of Guillemots as well as large numbers of Gulls were in association. Two different types of feeding dive were observed in Razorbills and Guillemots as well as a significant preference amongst Razorbills for unidirectional diving. The behaviour of both species on the water is described and the functional significance of bird groupings is discussed.
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Source: Gaston & Jones (1998), p. 129
"Cayford (1981) noted that they [Razorbills] tend to be more evenly spaced than Common Murres where feeding in association. The characteristically upend more than murres in submerging; 90% of those watched by Cayford oriented towards the sun while diving, suggesting that the direction of light could affect their ability to detect prey."
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