Journal Contents

Atlantic Seabirds Vol 7, No. 3 (2005)

Schreiber, J. & Kissling, W.D.2005. Factors affecting the breeding success of Arctic Terns Sterna paradisaea in a colony at Kaldbaksbotnur, Faroe Islands. Atlantic Seabirds 7(3): 97-105

Food shortage and predation are the main factors limiting the breeding success of many colonial seabirds. The aim of this study was to examine whether they influence breeding success of Arctic Terns Sterna paradisaea in a colony of 99 breeding pairs at Kaldbaksbotnur on the island of Streymoy, Faroe Islands. In 2003, we investigated clutch size, hatching success, food provisioning to chicks, kleptoparasitism, and predation, and the number of fledged chicks. Clutch size was on average 1.65 (±0.48) eggs/clutch with a hatching success of 100%. Food provisioning rates were low with 0.47 (±0.18) feeds per nest per hour. Most prey items were small (c. 32 mm long), and terns showed high rates of intraspecific kleptoparasitism. Attacks by avian predators were occasionally observed, mainly by Herring Gulls Larus argentatus, but were unsuccessful in all observed cases. Counts of fledged chicks indicated average breeding productivity of 0.22 chicks per pair. Our results suggest that breeding success in this colony was mainly affected by food shortage, possibly limited sandeel Ammodytes spp. availability. Predation appears to be less important, but could occur at a low rate. The results are consistent with recent evidence showing that seabirds that feed on sandeels currently have limited breeding success in the North Atlantic region.

López Suárez P., Varo Cruz N., Hazevoet C.J. & López Jurado L.F.2005. Restricted nesting habitat and reproductive failure of Magnificent Frigatebirds Fregata magnificens in the Cape Verde Islands. Atlantic Seabirds 7(3): 107-120.

The islets of Baluarte and Curral Velho, off the island of Boavista, Cape Verde Islands, are the only two breeding sites of the Magnificent Frigatebird Fregata magnificens in the Western Palaearctic. This East Atlantic relict population was monitored from the summer of 1999 up to May 2006. Most surveys were conducted during the breeding season, i.e. from November to June. Total reproductive failure has been the rule over the last seven consecutive breeding seasons. Possible causes of nest failure are attributed to: 1) accidental egg loss during the incubation period; 2) hatching failure. The most plausible reasons explaining both causes are discussed. Human persecution and disturbance, restricted nesting habitat and isolation, and unsuccessful breeding has brought the population on the verge of extinction. The remaining population, thought to consist of 4-5 adult individuals (2 females and 2-3 males), is unlikely to survive on its own.

Horssen, P. van2006. Large numbers of Cape Verde Shearwaters Calonectris edwardsii off Santo Antão, Cape Verde Islands, in July 2005. Atlantic Seabirds 7(3): 121-126.

During systematic sea watching in the period 20-27 July 2005 at Ponta do Sol, Santo Antão, Cape Verde Islands, a total of 6653 Cape Verde Shearwaters Calonectris edwardsii were counted. Largest numbers were counted 2-2.5 hours before sunset. Main flight direction was east. Numbers of Cape Verde Shearwaters were low 1-1.5 hours after sunrise, with the main flight direction being west.

Lavers J.L., Muzaffar S.B. & Jones I.L.2005. Double white lines on the bill of the Razorbill Alca torda: remnants of an association with the extinct Great Auk Penguinus impennis? Atlantic Seabirds 7(3): 127-132.

One of the diagnostic features of the Razorbill Alca torda is the distinct white line running vertically across the bill. Here we report the presence of two white bill lines in 10 wintering Razorbills from Newfoundland, Canada in addition to a small number of unreported birds from museum collections and personal records. Populations of Razorbills across their range have been divided into two major subspecies based on morphological variation, although molecular studies do not support such a subdivision. Molecular phylogeny of the auks place Razorbills as the closest relatives of the extinct Great Auk Penguinus impennis. Multiple white bill lines were a characteristic of the Great Auk and we speculate that this variation in the bill marking in the Razorbill is an atavism, reflecting their common ancestry.

Dahl H.K., Barrett R.T. & Ims R.A.2005. Effects of supplementary feeding on provisioning and growth rates of Atlantic Puffin Fratercula arctica chicks in North Norway. Atlantic Seabirds 7(3): 133-143.

After many years of a gradual change in chick diet and a supposed deterioration in feeding conditions, chicks of Atlantic Puffins Fratercula arctica were fed 50g supplementary food per day (capelin Mallotus villosus) to test if they grew faster than control chicks, thus indicating that conditions really were suboptimal. Growth rates were, however, approximately the same as for control chicks through a near halving of provisioning rate by the experimental parents. This suggests that feeding conditions, despite a large change in diet composition, were still adequate for normal breeding.