ATLANTIC SEABIRDS

Contents and abstracts issue 1(1)
published June 1999

Hunter F.M. 1999. On the function of pre-laying breeding site attendance in the Northern Fulmar Fulmarus glacialis. Atlantic Seabirds 1(1): 3-16.

Northern Fulmars Fulmarus glacialis spend considerable periods of time at their breeding sites in the months before egg laying. In this study the function of pre-laying breeding site attendance was investigated. Three potential benefits of prolonged pre-laying colony attendance were considered: (1) site defence; (2) opportunities for engaging in either pair or extra-pair copulations (EPCs); and (3) mate defence. There was no evidence that the function of pre-laying colony attendance was site defence: sites were left unguarded for long periods during the pre-laying period and were not subsequently lost to conspecifics. Neither did it appear that individuals maintained a high frequency of attendance to engage in pair copulations. The available evidence is consistent with the idea that females attended the colony to engage in EPCs; females present at the colony on a high proportion of days during the pre-laying period were more likely to be involved in EPC attempts. Although the possibility that females attended the colony for an as yet unidentified reason and engage in EPCs simply because they were there could not be ruled out. It appeared that males attended the colony in an attempt to prevent their partners from engaging in EPCs. Males maintained a higher level of attendance than females throughout the pre-laying period and seldom left their female partners unaccompanied during the presumed fertile period.

Wood D. 1999. Microgeographical variation in the call of the male Manx Shearwater Puffinus puffinus. Atlantic Seabirds 1(1): 17-26.

The calls of male Manx Shearwaters Puffinus puffinus at two separate breeding areas on Bardsey Island, Wales were investigated. There was little difference between calls from the two subcolonies when call characteristics were compared separately, but a discriminant analysis placed 75% of the birds into their correct locality. The recent establishment of one of the subcolonies may be responsible for the call variation, rather than any functional explanation.

Hüppop O. & K. Hüppop 1999. The food of breeding Herring Gulls Larus argentatus at the lower river Elbe: does fish availability limit inland colonisation? Atlantic Seabirds 1(1): 27-42.

In a Herring Gull Larus argentatus colony on an island in the lower river Elbe, northern Germany, diet during the breeding season was investigated. Fish was found in 79% of all pellets, followed by crustaceans (39%, presumably Mitten Crabs Eriocheir sinensis only) and human refuse (10%). Overall, 77% of all pellets only contained fish and/or crab, suggesting that feeding was predominantly at the river bank near the colony. Of (potential) food remains other than pellets, 46% were fish, 19% gull eggs, 17% crustaceans, 10% small birds and 8% human refuse. The strong tidal rhythm of the adults’ attendance at the colony coincides with fishery activities at the river banks and supports their dependence on unwanted bycatches from fisheries. From this and other studies, there is strong evidence to suggest that the inland breeding distribution of Herring Gulls is limited by the availability of fish during the breeding season rather than by the availability of human refuse or by the lack of breeding habitats.

Heubeck M. 1999. The effect of a spring gale and a freak wave on a breeding group of Common Guillemots Uria aalge. Atlantic Seabirds 1(1): 43-47.

On 19 May 1997, during a north-easterly gale (force 8-9) an exceptionally large swell approached and swept across a rock platform with nesting Guillemots Uria aalge at Sumburgh Head (Shetland). A total of 27 eggs of 110 being incubated on 18 May were lost, but most pairs relaid within 13-20 days. Hatching success of replacement eggs was very low and none of the chicks fledged. The storm occurred too late in the incubation period for the replacement eggs to have been successful.