1 Institut f. Pharmazeutische Biologie, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 364, D-69120 Heidelberg, GERMANY, e-mail: Ten adres pocztowy jest chroniony przed spamowaniem. Aby go zobaczyć, konieczne jest włączenie w przeglądarce obsługi JavaScript. 2 Department of Avian Ecology, Wrocław University, Sienkiewicza 21, 50-335 Wrocław, POLAND, e-mail: Ten adres pocztowy jest chroniony przed spamowaniem. Aby go zobaczyć, konieczne jest włączenie w przeglądarce obsługi JavaScript.

Abstract. DNA fingerprinting or microsatellite PCR studies have disclosed that extra-pair paternity (EPP) is a regular and relevant phenomenon in socially monogamous species. Corresponding genetic data are tabulated for 119 species. Within a species, the EPP can vary between populations and years; it obviously depends on several environmental, ecological and sociobiological constrains. While these explanations can account for variation within certain species or genera, they fail if we look at EPP within the class Aves. We found, that the probability that both mates of a monogamous pair breed together in consecutive years (termed annual pair survival) appears to be negatively correlated with the degree of extra-pair fertilizations (EPF), i.e. longlived species, in which mates have a real chance to raise young together over several seasons show significant lower EPP than species which only mate for a single summer (including many songbirds). Our analysis thus provides another possibility to speculate on the function and benefits of extra-pair copulations (EPC). Data are also given on the evolution of mating systems in New World Blackbirds Icteridae and reed warblers (genus Acrocephalus) based on molecular phylogenies of these groups, indicating a high degree of convergent evolution.

Key words: mating systems, molecular studies, extra pair paternity, mate tenacity

Department of Biological Sciences, Columbia University, 1200 Amsterdam Avenue, Mail Box 5521, New York, NY 10027-7004, U.S.A., e-mail: Ten adres pocztowy jest chroniony przed spamowaniem. Aby go zobaczyć, konieczne jest włączenie w przeglądarce obsługi JavaScript.

Abstract. An integrated, holistic analysis of the avian jaw apparatus within the system of avian cranial kinesis shows a complex series of movements of the two jaws, rather than just a simple opening and closing of both jaws. Because of the complex arrangement of the jaw muscles, birds have achieved different adaptive configurations of these muscles for various movement combinations. Specialization of the several jaw muscles are correlated, nevertheless, with the different possible movements of both jaws, such as the evolution of the M. ethmomandibularis in parrots for independent raising of the lower jaw and the M. pterygoideus retractor in several avian groups for independent lowering of the upper jaw.

Key words: avian biomechanics, cranial kinesis, coupling mechanisms, jaw movements, jaw muscles

Institute of Zoology, University of Wrocław, Sienkiewicza 21, 50-335 Wrocław, POLAND, e-mail: Ten adres pocztowy jest chroniony przed spamowaniem. Aby go zobaczyć, konieczne jest włączenie w przeglądarce obsługi JavaScript.

Abstract. A novel, skeletal reconstruction of Archaeopteryx skeleton follows Heilmann's (1926) tradition in being based primarily on osteological evidence and free phylogenetic and functional preconceptions. Although the connection between the sternum and ribs remains unknown, a combination of positional and comparative evidence speaks for the presence of cartilaginous sternal ribs. The reconstructed rib cage is compatible with some levels of the airsac ventilation mechanics. The reconstructed segmental position (relative to the vertebral column) of the shoulder girdle at the level of 11th or 12th vertebra agrees with evidence from both modern birds and theropods. The wing must have been largely folded in the resting position, but the geometry and mechanism of wing folding remain conjectural. In its gait and stance, Archaeopteryx was more similar to the modern birds than to the theropods.

Key words: fossil birds, Archaeopteryx, palaeontologic reconstruction, avian skeleton

Department of Population Ecology, Universitetsparken 15, DK 2100 Copenhagen Ć, DENMARK, e-mail: Ten adres pocztowy jest chroniony przed spamowaniem. Aby go zobaczyć, konieczne jest włączenie w przeglądarce obsługi JavaScript.

Abstract. The usefulness of transmission and scanning electron microscopy for clarifying the finer details of feather morphology is exemplified. (1) The structure making a wing feather airtight is a ventral, membraneous extension of a barbule closing the gap between adjacent barbules. (2) The exposed part of the body plumage is a very open structure. This fact and the shape of barbules in transverse section suggest that water repellency is an important function of body plumage. (3) Two ways of producing colours resembling those of green vegetation by utilizing yellow carotenoids, blackish melanins, air and keratin are contrasted: a simple one in olive green feathers and a complex one in green feathers of Ptilinopus doves.

Key words: feather, morphology, airtightness, water repellency, colour

Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803-1715 U.S.A., e-mail: Ten adres pocztowy jest chroniony przed spamowaniem. Aby go zobaczyć, konieczne jest włączenie w przeglądarce obsługi JavaScript.

Abstract. The feather-bearing skin of birds differs fundamentally from the fur-bearing skin of mammals. Especially within the feather tracts, it contains much structural fat tissue in the dermis and the subcutaneous Fascia superficialis. These are separated from each other by an elastic membrane and are, together with the feather muscles, part of the hydraulic skeleto-muscular apparatus of the feathers. While feathers are raised by erector feather muscles and are returned to their resting position by the resilience of the surrounding fat tissue and an elastic membrane, the depressor feather muscles counteract external forces, such as air turbulences, thereby ensuring a smooth surface of the coat of feathers and reducing drag during flight. The coat of feathers itself creates fusiform body contours, which also reduce drag. Furthermore, subcutaneous fat bodies are strategically placed to ensure an even draping of the skin over the body and, thereby, contribute to streamlined body contours. The subcutaneous fat bodies and the dermal depressor muscles are part of the unique characteristics of the avian integument and have evolved under the selective regime for streamlining of body contours and surface as a precondition for the evolution of avian flight.

Key words: avian biomechanics, integument, feathers, fat, flight, evolution

Institut f. Vergleichende Verhaltensforschung der Österreichischen Akademie der Wissenschaften, Savoyenstraße 1a, A-1160 Wien, AUSTRIA, e-mail: Ten adres pocztowy jest chroniony przed spamowaniem. Aby go zobaczyć, konieczne jest włączenie w przeglądarce obsługi JavaScript.

Abstract. Frugivory is widespread among birds and, at first glance, it is difficult to suggest states of external characters that would separate frugivorous birds from omnivores and carnivores. In the literature it has been suggested that body size and gape width increase with frugivory. It also has been stated that powerful morphological constraints act on behavioural differences among fruit-eating birds. This relates mainly to the way fruits are obtained by the birds, namely either on the wing or from a perch. We analysed behaviour and external morphological characters of Neotropical birds in a lowland rain forest in southern Venezuela to address these problems. Morphologically speaking, frugivores formed an ill defined subset of this avian community. Body size and gape width did not show a consistent relationship with frugivory. Reaching out and down, as well as taking fruits on the wing were the most common techniques used apart from simple gleaning. Body size constrains the evolution of corresponding characters. Evolutionary speaking, there are many roads to frugivory and only careful analyses of behavioural observations, and ecological data, paired with morphological considerations can uncover the general rules behind this diversity.

Key words: frugivory, ecomorphology, behaviour, evolution, Neotropical region,

Institute of Systematic Zoology and Evolutionary Biology, Friedrich-Schiller-Universität, Erbertstrasse 1, D-07743 Jena, GERMANY, e-mail: Ten adres pocztowy jest chroniony przed spamowaniem. Aby go zobaczyć, konieczne jest włączenie w przeglądarce obsługi JavaScript.

Abstract. Evolutionary biology presumes that organ capacities match their natural loads. Therefore, organ systems are expected to show a reversible, repeatable and rapid phenotypic response to fluctuating conditions that is directional and scaled. In this study, phenotypic responses of the gizzard of adult Japanese quails Coturnix japonica to experimental mismatches of load and capacity were tested by a series of diet-switching experiments (involving an increased content of non-digestable fibre, NDF, in the diet). The results of all experiments were in accordance with the predictions made from the hypothesis that there is matching between loads and capacities: (1) the observed phenotypic responses are directional and scaled to the demands, i.e. increasing NDF elicits an increase in gizzard size. When the proportion of NDF in the diet was raised from 1% to 45%, the gizzard was more than twice as large as in the control group; (2) size responses were reversible, and reduced NDF was followed by a decrease of gizzard size; (3) phenotypic responses could be elicited repeatedly in three successive trials; (4) excess capacities were down-regulated and insufficient capacities were up-regulated; (5) the responses followed changes of loads with almost no time lag, with size changes measurable within 24 hours.

Key words: phenotypic transformation, gastrointestinal tract, nutrition, diet-switching, functional anatomy, Japanese quail Coturnix japonica

Department of Engineering and Natural Sciences, Division of Bilogy, Vaxjo University, S351 95 Vaxjo, SWEDEN

* Corresponding author: e-mail: Ten adres pocztowy jest chroniony przed spamowaniem. Aby go zobaczyć, konieczne jest włączenie w przeglądarce obsługi JavaScript.

Abstract. Avian postnatal growth can be treated as a process where birds undergo changes in form due to differential growth rates of their different organs and tissues. These changes are reflected in the morphology and physiology of the animal. In the present study we compare early embryonic development, especially somitogenesis and muscle cell formation, in birds from lines of quail exhibiting different patterns of postnatal growth. We use classical staging techniques that use developmental landmarks to categorize embryonic maturity as well as morphological measurements of specific tissues. These techniques were combined with immunodetection of somite specific gene products to test the hypothesis that differences in postnatal development would be reflected in patterns of embryonic tissue partitioning.

Key words: Quail Coturnix coturnix japonica, embryonic development, sonitogenesis, myotome formation

Dept. of Vertebrate zoology and Zvenigorod Biological Station of Moscow University, 119899 Moskow, RUSSIA, e-mail: Ten adres pocztowy jest chroniony przed spamowaniem. Aby go zobaczyć, konieczne jest włączenie w przeglądarce obsługi JavaScript.

Abstract. The level of maximum food energy or maximal existence metabolism (MPE) is 1.3 times higher in passerines than in non-passerines, which agrees with the ratio of their basal metabolic rates (BMR). The optimal ambient temperature for maximizing productive processes (e.g. reproduction, moult) is lower for passerines than for non-passerines, which allows passerines to have higher production rates at moderate ambient temperatures. This may explain variation in bioenergetic parameters along latitudinal gradients, such as the ecological rule of clutch size (or mass) increase in the northern passerine birds. The increased potential for productive energy output in the north may allows birds to moult faster there, as well. This phenomenon allows passerine birds to occupy habitats of widely fluctuating ambient temperatures in comparison with non-passerine birds of similar size. Passerines have more effective system for maintenance of heat balance at both high and low temperatures. The high metabolism and small body sizes in passerines are consistent with development of omnivory and ecological plasticity. Among large passerines the unfavourable ratio of MPE to BMR should decrease energy available for productive processes. This consequence limit both reproductive output and the development of long migration (especially in Corvus corax).

Key words: basal metabolic rate (BMR), existence metabolism, allometric analysis, mobility

1 Zoological Laboratory, University of Groningen, P.O. Box 14, 9750 A. A. Groningen, THE NETHERLANDS, e-mail: Ten adres pocztowy jest chroniony przed spamowaniem. Aby go zobaczyć, konieczne jest włączenie w przeglądarce obsługi JavaScript. 2 Depatment of Evolution, Ecology and Organismal Biology, Ohio State University, 1735 Neil Avenue, Columbus, OH 43210, USA

Key words: birds, basal metabolic rate, field metabolic rate, water flux, desert

1 Netherlands Institute for Sea Research (NIOZ), P.O. Box 59, 1790 AB Den Burg, Texel, THE NETHERLANDS 2 Centre for Ecological and Evolutionary Studies, Zoological Laboratory, University of Groningen, P.O. Box 14, 9750 AA Haren, THE NETHERLANDS 3 Department of Bological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, B. C. V5A 1S6, CANADA 4Australian School of Environmental Sciences, Griffith University, Nathan, Qeensland, 4111, AUSTRALIA * Corresponding author: e-mail: Ten adres pocztowy jest chroniony przed spamowaniem. Aby go zobaczyć, konieczne jest włączenie w przeglądarce obsługi JavaScript.

Abstract. Shorebirds show large interspecific variation in the relative size of the stomach, and especially of the muscular part, the gizzard. Much of this variation can be explained by their diet. Species feeding mainly on hard-shelled prey such as bivalves and gastropods have large stomachs; those feeding on soft-bodied prey such as worms have small stomachs. Within a species, diet- and migration-induced changes in stomach size can occur. Our studies on this intraspecific variation have focused on two mollusc-specialists, the Red Knot Calidris canutus and the Great Knot C. tenuirostris. Both are renowned for long-range flights between their arctic or sub-arctic alpine breeding grounds and a variety of coastal wetlands. Feeding mainly on shellfish ingested whole, both knot species have large stomachs, but changing diets easily lead to apparently adaptive modifications. In addition, the demands imposed by flights of many thousand kilometres may induce reductions in stomach size. Using ultrasonography we have begun to experimentally disentangle the causal relationships between diet, season and stomach size in Red Knots. A soft diet can induce stomach reductions of 50% within a week, and such changes are reversible. Studies on radiomarked birds in the Wadden Sea emphasize that variations in stomach size are correlated with prey and patch choice in the field.

Key words: diet, migration, stomach, flexible organ size, Red Knot Calidris canutus, Great Knot Calidris tenuirostris

1 Institut f. Vogelforschung "Vogelwarte Helgoland", Wilhelmshaven, GERMANY, present adress: Dept. de Biologia Animal (Vertebrats), Univ. de Barcelona, Av Diagonal 645, Barcelona-08028, SPAIN, e-mail: Ten adres pocztowy jest chroniony przed spamowaniem. Aby go zobaczyć, konieczne jest włączenie w przeglądarce obsługi JavaScript. 2 Dept. de Salut Pública (Bioestadística), Univ. de Barcelona, SPAIN 3 Dept. de Biologia Animal (Vertebrats), Univ. de Barcelona, SPAIN

Abstract. The seasonal decline in egg-volume on the basis of the individual changes in 35 known-age female Common Terns Sterna hirundo was studied with data available for 3-6 years. Interindividual differences were significant for both laying dates and egg-volume. Thus, to examine whether the decline was an effect of an assortment of females with the timing of breeding according to their individual egg-volume, the individual values of laying date were correlated with egg-volume. Correlation was not significant, suggesting that seasonal decline in egg-volume was not due to interindividual differences. Instead, egg-volume showed a gradual decrease with the progress of the season at intraindividual level i.e. the later an individual female laid in the season the smaller was the egg-volume. Moreover, the seasonal decline in egg-volume was not due to a simultaneous increase in egg-volume with an advancement of the timing of breeding with age, since the rate of seasonal decrease in egg-volume was similar for young and old birds. Individual average of laying date accounted for 22% of the individual average of fledgling production whereas egg-volume was not significantly correlated with fledging production. Thus, it is suggested that seasonal decline in egg-volume is a non-adaptive consequence of physiological effect of condition on both timing of breeding and egg-volume.

Key words: egg-volume, laying date, individual age, Common Tern Sterna hirundo

Department of Zoology, Pedagogical University, Arciszewskiego 22b, 76-200 Słupsk, POLAND

Abstract. During the 25 seasons (1974-1998), the breeding success of Collared Doves was determined by tracing the fates of 7882 nests found in S3upsk, Northern Poland. The kind of losses recognized were: complete nesting failures (CNF) and partial losses (PL), where only one nestling left the nest. Total breeding losses (TBL), were estimated by comparing the estimated total number of eggs laid (TNEL), with the total number of young fledged. In different years CNF varied from 51.8 to 75.7% ( = 61.1, SD = 5.1, n = 25 seasons, CV = 8%) while PL accounted for between 4.3 and 11.8% ( = 8.2, SD = 1.6, n = 25, CV = 19.5 %) of all eggs laid. TBL amounted to between 60.9 and 80% ( = 69.3, SD = 4.3, n = 25, CV = 6.2 %) of TNEL, and was highest at the beginning (February-April) of the breeding season, and at the end (September-October). The losses suffered during incubation ( = 70.6%, SD = 10.3, n = 25, CV = 15%) were much higher than at the nestling stage ( = 29.4%, SD = 10.3, n = 25, CV = 35%). Rooks and Jackdaws were the main nest predators of the Collared Dove population in S3upsk, while Magpies and domestic cats were less effective predators.

Key words: Collared Dove Streptopelia decaocto, breeding losses, urban ecology, predation.

Netherlands Institute of Ecology, Centre for Terrestrial Ecology, P.O. Box 40, NL 6666 ZG Heteren, THE NETHERLANDS, email: Ten adres pocztowy jest chroniony przed spamowaniem. Aby go zobaczyć, konieczne jest włączenie w przeglądarce obsługi JavaScript.

Abstract. Some models of central place foraging relate the time taken to deliver a prey to the selectivity of the forager. If birds have to travel longer, they are expected to take only larger prey. Prey selectivity may also increase if birds have more time available for search activities. I tested this last hypothesis by experimentally increasing the food available to Blue Tits during young rearing. Insect larvae were offered to breeding adults from egg hatching to fledging of the young. Provisioning rates and prey size were studied by videotaping. In experimentally overfed broods, part of the additional food was delivered to their nestlings by the adults, while the rate of feeding with natural prey decreased compared to unmanipulated pairs. Overfed males delivered larger insect larvae than control males, while females showed no response to the treatment. Overfed males could deliver larger prey at late chick ages (when presumably the chicks' demand is higher) than controls, suggesting that control males were time- (or energy) constrained. Moreover, overfed parents appeared to choose relatively more prey that may be important in the chicks' diet. The results show that prey selectivity is related to time (or energy) budgets.

Key words: Blue Tit Parus caeruleus, central place foraging models, minimum acceptable prey size, videotaping.

1 W. Stefanski Institute of Parasitology, Polish Academy of Sciences, Twarda 51/55, 00-818 Warszawa, POLAND, e-mail: Ten adres pocztowy jest chroniony przed spamowaniem. Aby go zobaczyć, konieczne jest włączenie w przeglądarce obsługi JavaScript. 2 Museum and Institute of Zoology, Polish Academy of Sciences, Wilcza 64, 00-679 Warszawa, POLAND, e-mail: Ten adres pocztowy jest chroniony przed spamowaniem. Aby go zobaczyć, konieczne jest włączenie w przeglądarce obsługi JavaScript. 3 Dept of Ecology, Institute of Zoology, University of Warsaw, Krakowskie Przedmieście 26/28, 00-927 Warszawa, POLAND

Abstract. Nestlings' condition parameters (body weight, tarsus and wing length) of Starling breeding in nest-boxes of various sizes were studied during two years. Two types of nest-boxes were used: normal - typical for that species, (bottom size 195 cm2, depth 22 cm) and 20-25% smaller. It was found that Starling didn't adjust their clutches to nest-box size. Also number of fledgelings was not related to nest-box size. Significant differences between nestling development in normal and smaller nest-boxes were found only during the first days of life, when nestling growth is intensive. In older stages of nestlings development those diferences dissappeared.

Key words: Starling Sturnus vulgaris, nest boxes, nest site size, nestlings condition

1 Forschungsstelle f. Ornithologie der Max-Planck Gesellschaft, Vogelwarte Radolfzell, Schlossallee 2, 78315 Radolfzell, GERMANY 2 Universitaet Freiburg, Biologie 1, Hauptstr. 1a, 79104 Freiburg, GERMANY * Corresponding author: Ten adres pocztowy jest chroniony przed spamowaniem. Aby go zobaczyć, konieczne jest włączenie w przeglądarce obsługi JavaScript.

Abstract. Males Aquatic Warblers used three different song types. Playback experiments revealed, that A-type song had an intrasexual function, while C-type song seemed to serve intersexual communication. Song flight contained a higher portion of C-song than spontaneous song. Song flight rate was not constant throughout the breeding season with a maximum in the absence of receptive females. The range use of both sexes was studied using radio-telemetry during two breeding seasons. Males used home ranges of up to 8 ha in size. These home ranges overlapped up to 74% with the ranges of other males. Females used isolated patches of 2.8 to 6.4 ha within activity ranges of 100-160 ha during the mating period. Seasonal variation in mobility of males was correlated to the presence of receptive females. The diurnal mobility of males was constant during the day and decreased after 20:00 when males participated in an evening chorus.

Key words: mating system, playback experiments, song activity, spatial behaviour, territoriality

1 Department of Zoology and Hydrobiology, University of Tartu, Vanemuise 46, Tartu, 51014, ESTONIA 2 Nigula Nature Reserve, Pärnu St. 2, Kilingi-Nomme, 86303, ESTONIA corresponding author, e-mail: Ten adres pocztowy jest chroniony przed spamowaniem. Aby go zobaczyć, konieczne jest włączenie w przeglądarce obsługi JavaScript.

Abstract. Wild birds breeding in acidified areas may have difficulties obtaining sufficient calcium for their eggshells, and shortage of land snails is shown to be the cause. The study found experimental evidence that Ca deficiency may affect reproductive traits also in birds breeding in non-acidified but naturally base-poor habitats. Positive effects of calcium supplementation on the egg volume, shell thickness, start of laying and fledglings' parameters of Great Tits Parus major and Pied Flycatchers Ficedula hypoleuca breeding in base-poor pine forests in Estonia were revealed. The adverse effects of calcium shortage seem to be more pronounced in the years with the most unfavourable breeding conditions. Authors suggest that in such years birds may respond to calcium shortage by postponing egg-laying. The cost of egg formation in base-poor areas might be much higher than has been estimated on the basis of the energy and protein content of eggs. This fact should be considered more seriously in life history models of wild birds.

Key words: calcium, egg, Pied Flycatcher Ficedula hypoleuca, Great Tit Parus major, calcium-poor habitat

Institute of Nature Conservation, Polish Academy of Sciences, Lubicz 46, 31-512 Kraków, POLAND, e-mail: Ten adres pocztowy jest chroniony przed spamowaniem. Aby go zobaczyć, konieczne jest włączenie w przeglądarce obsługi JavaScript.

Abstract. In 1991-1995 fourteen morphological traits of Great Tit breeding in a nest boxes were measured. Their relation to fitness was checked in elements of a tit's bilogy: survival of young to first reproduction, competition for nesting places, first and second broods, lifetime survival and reproduction. Selection intensity (i) was calculated for principal components of body size. Phenotypic selection evidences were mainly singular. Comparison of body size of individuals recruited to the studied population revealed that males of larger body size were recruited to the population. An experiment showed that individuals with larger bills won competition for nest boxes (i for bill length ranged from 0.05 in males to 0.34 in females). Clutch size depended positively on the measurements of males (i = 0.07 and i = 0.11 respectively), and negatively on the body measurements of females during the first brood (i = -0.08 in 1995). During the second broods there was a positive trend in relation between body size of parents and young condition (for females i = 0.05 and i = 0.02 respectively, for males i = 0.08 in 1992). Intensive selection on body size (i = -0.34 for males, i = -0.61 for females), due to a catastrophic impact of bad weather was recorded as well. Analysis of lifetime data on the longevity and mean breeding success per year, revealed for cohort of individuals a strong negative selection on body size in females (i = -0.46 with regard to breeding success, i = -0.16, longevity) and positive selection on forearm length in males (i = -0.128, longevity). For 8 cases of selection, its direction in males favoured larger body size (7 cases), whereas in females selection directions were differentiated (3 positive, 3 negative). This pattern was concordant with sexual size dimorphism in the studied population.

Key words: Great Tit Parus major, phenotypic selection, body size, sexual size dimorphism