Volume 46• Number 2 • 2005

61 All-year occurrence of the Herring Gull Larus argentatus, Caspian Gull L. cachinnans
    and Yellow- legged Gull L. michahellis in central Poland.
    Grzegorz Neubauer, Marcin Faber, Magdalena Zagalska-Neubauer

Abstract: All-year surveys of gulls, performed at the rubbish dump in Toruń (37 counts) and Jeziorsko Reservoir (39 counts) in 2001-2004, clearly show that the three large gull species are characterized by strongly different patterns of occurrence, number dynamics and age structure. Total numbers of gulls were the lowest in April-June, and the highest in September-November, in Toruń also in winter months (January-February). The percentage of particular species in the whole group varied depending on the season. The Herring Gull predominated during the autumn or winter (up to 1950 inds in Toruń and 1500 at Jeziorsko Reservoir), whereas the Caspian Gull was the commonest species in the summer-autumn period (up to 1130 inds at Jeziorsko Res. and 330 in Toruń). The Yellow-legged Gull occurred almost exclusively between June and November (up to 115 inds at Jeziorsko Res. and 420 inds in Toruń ). During the summer, Herring Gulls were scarce in both sites (15-35% of all gulls in Toruń and 1-11% at Jeziorsko Res.). Additional counts made in the Konin area (central Poland ) and at Żywiecki Reservoir (southern Poland ) as well as the distribution of ringing recoveries from all three species confirm the results obtained.

77 Changes in the breeding avifauna of the " Lake Łuknajno " Biosphere Reserve in 1982-
     2002. Grzegorz Osojca

Abstract: In 1999-2002 the species composition and numbers of particular breeding birds of Lake Łuknajno and the adjacent territories, an area covering ca 710 ha of the Biosphere Reserve, were assessed. The qualitative and quantitative changes found in the bird fauna of the region were analyzed in comparison with data for 1982-1987 (Bukaciński & Jabłoński 1992a). Substantial impoverishment of the avifauna was revealed, since in 1999-2002 only 97 breeding species were recorded, relative to 119 observed in 1982-1987. Within a 20-year period 12 species (Red-necked Grebe Podiceps grisegena, Black-necked Grebe P. nigricollis, Little Bittern Ixobrychus minutus, Grey Heron Ardea cinerea, Teal Anas crecca, Pintail A. acuta, Little Ringed Plover Charadrius dubius, Ringed Plover Ch. hiaticula, Black-tailed Godwit Limosa limosa, Redshank Tringa totanus, Black-headed Gull Larus ridibundus and Aquatic Warbler Acrocephalus paludicola) withdrew from the " Lake Łuknajno " reserve, and further 10 species disappeared from the surroundings of the lake. Abundance of 38 species (particularly waterbirds) dropped conspicuously. The factors responsible for such serious impoverishment of the avifauna are unclear. In 1982-2002 very essential environmental changes occurred, which may have affected the bird fauna of Lake Łuknajno and the adjacent areas: considerable reduction of agriculturally managed land within the lake catchment area (secondary succession), primary succession of the lake and the appearance of the American Mink Mustela vison.

89 Rare birds recorded in 1999-2003 in Western Pomerania.
    Zbigniew Kajzer, Sebastian Guentzel, Michał Jasiński, Marcin Sołowiej

Abstract: In 1999-2003 first breeding records of the Whooper Swan Cygnus cygnus, Whiskered Tern Chlidonias hybrida and Tengmalm's Owl Aegolius funereus were made in Western Pomerania , and after 42 years of absence the Peregrine Falco peregrinus reappeared in the breeding avifauna of the region. A few species which had rarely been recorded from this part of Poland before, such as the Great White Egret Egretta alba, Marsh Sandpiper Tringa stagnatilis or Mediterranean Gull Larus melanocephalus, were recorded to regularly occur here. On the national scale, numerous observations of the Barnacle Goose Branta leucopsis, Purple Sandpiper Calidris maritima and Rock Pipit Anthus petrosus are worth noting. The most interesting records include the first regional observations of the Shag Phalacrocorax aristotelis, Red-breasted Goose B. ruficollis, Pectoral Sandpiper C. melanotos, Syrian Woodpecker Dendrocopos syriacus, Red-rumped Swallow Hirundo daurica and Black-headed Wagtail Motacilla flava feldegg. Among the other interesting records, observations of the following species should be mentioned: Steller's Eider Polysticta stelleri, Griffon Vulture Gyps fulvus, Great Bustard Otis tarda, Kentish Plover Charadrius alexandrinus, Dotterel Ch. morinellus, Great Skua Stercorarius skua and Arctic Redpoll Carduelis hornemanni.

Overviews

105 Costs and constraints in acoustic communication.
     Tomasz S. Osiejuk

Summary: The author presents basic types of costs associated with acoustic communication: energetic, time- and predation-related. Costs of the sender and receivers are discussed separately when necessary. The author shows how difficult it is to measure real communication costs outside a laboratory, indicating where and why our knowledge is still insufficient. In the case of energetic costs, the author presents several studies which revealed contradictory findings. Despite the fact that energetic costs of singing have been estimated in several species and in different conditions there is still no agreement on how energy demanding singing is. The loss of time is important cost of singing and birds apply different techniques to optimize time spent on singing and on different life activities such as foraging, vigilance etc. A few examples are presented in order to show the range of between-species variation. Risk of predation as a cost in acoustic communication is discussed mostly in the light of begging calls and conflict between nestlings and parents. The classification of receiver-dependent and -independent costs is also well-illustrated, and cost-based classification scheme of acoustic communication systems is presented. Independent costs (or necessary costs) of signalling are those which are necessary to make regardless of receiver reaction or even lack of reaction, e.g. investments in organs or special structures which enable to produce sounds is such a kind of cost. In evolutionary scale, selection promotes such communication systems where independent costs are lower than benefits from signalling. However, there is another class of costs, called incidental costs. In this case, the costs and benefits are receiver-dependent. For instance signalling aggression may have different costs when the receiver is strong (possible attack) and weak (possible retreat). These costs are shaped by receiver reaction, but when we focus on the whole system, we understand that costs depend also on the initial decision of the signaller and its ability to recognize strength (or motivation) of the receiver. Cost-based classification scheme is a special way of thinking about communication and its evolution. The author summarizes and gives examples of different signal types, such as index, quality handicap, general handicap, vulnerability handicap and, last but not least, conventional. This types of signals differ clearly according to costs, signal design and information contents. Especially the conventional signalling is worth mentioning as in this system signal design is very specific. There is an arbitrary relationship between signal design and meaning, and costs which stabilize such systems are based on receiver retaliation. Finally, the differences between costs and constraints in communication are discussed. The paper is a general introduction, which should make easier thinking about costs and constraints in avian vocal communication at evolutionary scale.

Notes

121 The Long-eared Owl Asio otus diet in agricultural and forest landscape.
     Michał Żmihorski

Summary: Winter diet of the Long-eared Owl was analyzed in two habitats within the Masovian Lowland, central Poland . Pellets were collected at two sites: 405 prey items came from forest areas ( Kampinos National Park ) and 59 from agricultural landscape (Jelonki). Both samples represent the diet from winter 2001/2002. The proportion of the Common Vole Microtus arvalis in the diet in the KPN was lower as compared with the value obtained for Jelonki. This species composed ca 60% of prey consumed in agricultural landscape and ca 30% in forest landscape. However, due to the high consumption of the Tundra Vole M. oeconomus in the KPN, the total share of Microtidae was similar.

127 Mystery bird 39: Least Sandpiper Calidris minutilla.
     Jan Lontkowski

Reviews

129 Jerzak L., Kavanagh B.P., Tryjanowski P. (eds.). 2005. Ptaki krukowate Polski (Corvids of Poland).
     Bogucki Wydawnictwo Naukowe, Poznań . Andrzej Wuczyński