ATLANTIC SEABIRDS

Contents and abstracts issue 1(2)
published October 1999

Grémillet D. & Cooper J. 1999. Stomach temperature variations in a Cape Gannet Morus capensis as an index of foraging activity and feeding rates. Atlantic Seabirds 1(2): 49-56.

Animal-mounted electronic devices are powerful tools for studying seabirds at sea. The potential handicap of additional load should be minimised, while nevertheless measuring relevant field data. In this paper, we show how records from a 16g stomach temperature logger may be used to calculate the key values of foraging effort and feeding rate in an avian marine predator.

Kubetzki U., Garthe S. & Hüppop O. 1999. The diet of Common Gulls Larus canus breeding at the German North Sea coast. Atlantic Seabirds 1(2): 57-70.

The diet of Common Gulls Larus canus was analysed from pellets and faeces during the breeding period in 1995. Three geographically well-separated colonies were selected: one located close to the open North Sea (Amrum Island), one at the inner edge of the Wadden Sea (Nordstrandischmoor Island), and one in the tidal river Elbe (Lühesand Island). The birds fed upon a large variety of food types. In the two colonies adjacent to the sea, prey types from the tidal flats were most numerous (mainly crustaceans, polychaetes, bivalves). Gadids and Smelt Osmerus eperlanus were the fish identified most often, whereas discards from fisheries were relatively important during the early incubation period on Amrum and Nordstrandischmoor. Terrestrial food was also taken (earthworms, insects) but was less important. On Lühesand, in contrast, Common Gulls fed predominantly on terrestrial food (earthworms, insects, mammals and fruits). These birds hardly utilised the river Elbe and associated freshwater tidal flats. The diet changed in all three colonies over the breeding period. The proportion of mammals increased while that of fish and bivalves (only the two colonies close to the coast) decreased. On Lühesand, a considerable proportion of the pellets consisted of cherry stones during the chick-rearing period. Common Gulls were relatively widely distributed in the inner German Bight but all major concentrations were located close to land, chiefly in front of the mouths of the rivers Elbe and Weser. Common Gulls (up to 150 individuals) regularly attended the inshore shrimping vessels.

Jensen J.-K., R.L. Palma & B. Zonfrillo 1999. Feather lice from Sooty Shearwaters Puffinus griseus in the Faroe Islands. Atlantic Seabirds 1(2): 71-76.

Seven species of lice (Insecta: Phthiraptera) were found on 41 dead Sooty Shearwaters (Puffinus griseus) collected from two localities around the Faroe Islands in 1997. Four species (Ancistrona vagelli, Austromenopon paululum, Halipeurus diversus and Trabeculus hexakon) are regarded as regular ectoparasites on Sooty Shearwaters. The other three species (Halipeurus gravis gravis, Naubates harrisoni and Saemundssonia peusi) are treated as natural stragglers from other petrels. Possible explanations for the transferral of the three straggling louse species from their regular hosts to Sooty Shearwaters are discussed.

Silcocks A.F. 1999. The size of the breeding population of Manx Shearwaters Puffinus puffinus on Bardsey (Wales) in 1996. Atlantic Seabirds 1(2): 77-84.

In late May and early June 1996 a whole- island survey of Manx Shearwaters was undertaken on Bardsey. All apparently occupied burrows (AOB) were counted, resulting in a total of 6927 AOBs. An additional survey of shearwaters nesting amongst gorse bushes was carried out using a call playback technique and revealed an additional 101 pairs. A comparison of the accuracy of the two censusing techniques revealed a disparity of under 10% in a selected survey area. A future monitoring program for the Manx Shearwaters on Bardsey is proposed.

Camphuysen C.J. 1999. New feeding technique of Great Cormorant Phalacrocorax carbo sinensis at beam trawlers. Atlantic Seabirds 1(2): 85-90.

Since the mid 1980s, following a marked range expansion and dramatic population growth, continental Great Cormorants Phalacrocorax carbo sinensis, increasingly use Dutch coastal waters as a feeding area. Fishing Great Cormorants are now commonly seen at sea within 15 km of the nearest coast and small numbers disperse further out to sea. Small beam trawlers, mainly targeting Brown Shrimp Crangon crangon, are the dominant fishery of these waters and Great Cormorants were soon seen to attend these vessels. Recent observations indicate that, in contrast to other ship-following seabirds, Great Cormorants forage continuously during the towing of nets, even when no discards are produced on board. It is suggested that these birds prey on disturbed fish or other prey, just behind the moving nets that rupture the bottom. This feeding technique has not previously been observed in any species of seabird in the North Sea.

Camphuysen C.J. & Reid J.B. 1999. Trends in seabird systematics: recent sometimes conflicting decisions of BOURC and CSNA. Atlantic Seabirds 1(2): 92-94.

In the presentation of his list of Recent Holarctic Bird Species, Voous (1973) was convinced, after consultation with many ornithologists from all parts of the world, that the time had not arrived for an attempt to reach reasonable agreement on a list of bird species of the world. Today, more than 25 years and several world lists later, and while the enormous undertaking the Handbook of the Birds of the World (Del Hoyo et al.[in series]) is well under way, consensus has still not been reached. While Voous' lists (1973, 1977ab) have been the standard for many years, several amendments have been published by the BOU Records Committee (BOURC) and more recently by the Dutch committee for avian systematics (CSNA). For Atlantic Seabirds, a joint venture between a UK and a Dutch organisation, this means that different lists and sequences, even different systematic principles, have been adopted in either country.

The debate will go on, no doubt. Meanwhile, there is scope for confusion and there is an increasing risk for misunderstanding. For example, most ornithologists refer to the Lesser Black-backed Gulls Larus fuscus as a polytypic species that includes a very black, small and slender nominate race in the north and east of Europe, and two paler, bulkier races around the North Sea (L.f. graellsii and L.f. intermedius). The CSNA considers the Baltic Gull L. fuscus and Lesser Black-backed Gull L. graellsii as specifically distinct, and 'intermedius' is considered conspecific with graellsii (Sangster et al. 1999). Similar decisions were published for the soft-plumaged petrel complex Pterodroma mollis / maderia / feae, for Cory's Shearwaters Calonectris diomedea / borealis / edwardsii, Manx Shearwaters Puffinus puffinus / yelkouan / mauretanicus, the herring gulls/yellow-legged gull complex Larus argentatus / cachinnans / michahellis. Previously, the BOURC has suggested changes to the British and Irish List (e.g. BOURC 1991, 1998). For example, Sula bassana was changed to Morus bassanus, a proposal adopted by CSNA only in 1997. The mediterranean subspecies of Manx Shearwater was accorded species status Puffinus yelkouan (including subspecies mauretanicus), while the nominate was now considered monotypic. However, CSNA has split this complex (for Europe) into three distinct taxa (Table 1; Sangster et al. 1999). Attempts for a definitive (European) list are now under way, but there are no grounds for believing that consensus will be reached soon. We hope to regularly inform readers of Atlantic Seabirds of recent developments and decisions by various authorities in this section. In this first contribution, foregoing differences are highlighted. An overview of the main differences between The British and the (new) Dutch list are summarised in Table 1, showing names proposed by Voous (1973), names used on the British List (BOURC 1998), and proposals by the CSNA (Sangster et al. 1999), which have recently been adopted by the Netherlands Ornithologists' Union (NOU). Underlying the main differences are different systematic principles adopted by either committee. While CSNA has decided to use the Phylogenetic Species Concept (PSC), the BOURC is apparently still working along the lines of the Biological Species Concept (BSC), but it is not clear which taxonomic philosophy forms the basis of their decisions. In the absence of international consensus in these matters, we will have to live with different systems and conflicting lists.