Volume 18 - N. 1
June 1994

Volume 18 - N. 1

  1. Avocetta n.19 (1) - 1994

    Abstract     Read Article       Download
    23 528
  2. Clutch size of the Great Tit Parus major  and the Blue Tit Parus caeruleus  in some areas of Centrai Italy


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    17 48

    Small values of clutch size were observed for both species in ali the study stations, as compared
    with other European areas located at higher latitude; these results could be related to the lower seasonality
    of food resources in Mediterranean area. In some sites preliminary data show a high presence of youngsters
    among the breeders; considering also the small effect of competitive factors and predation on clutch size, a
    trade-off between reproduction and survival does not appear to be important. As far as cJutch size variations
    among the study areas are concerned, habitat features, density of breeders and laying date seem to play a
    decisive role. Clutch size does not decrease with altitude. Food availability might produce the observed
    differences in breeder density.

  3. Prey selection by parents and chicks of the Little Tern Sterna albifrons.


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    16 47

    The diet of Little Tern chicks was studied in order to analyze the prey choice of a species that
    carries single, unbroken prey to its nest. Chicks less than 5 days old were fed with thinner fish than chicks
    older than IO days. The average prey size was smaller for younger chicks. Prey left uneaten by chicks
    included larger, bulkier fish, shrimps and potentially poisonous fish. The parents select prey according to
    the chicks’ ability to swallow, and a further selection is accomplished by the chicks themselves.

  4. Radio-tracking small aerial foraging birds:a preliminary study of the Sand martin  Riparia riparia


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    24 63

    A method is described for attaching radio-tags to small aerial feeding birds, illustrated with data
    from three Sand martins (Riparia riparta). The radio transmitters had no measurable effects on the subjects.
    Foraging range, and roost sites were recorded for a pair rearing chicks, which had a similar nest visit rate as
    a control pair in a neighbouring nest. The birds often foraged close to water, and the male used a larger area
    than the female. The pair roosted in agricultural crops several Kilometres from their nest, while the third
    bird (a mate guarding male) was found roosting in the burrow that it defended during the day. Some future
    applications of radio-tracking lO small aerial foraging birds are discussed.

  5. La popolazione di  Larus cachinnans michahellis nidificante nella città di Trieste.


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    18 49

    Urban nesting by Yellow-Legged Herring Gulls in the city ofTrieste was first observed in 1987.
    The number of nests on the top of buildings increased by 49.9% on average each year since 1988, this
    increase may dictate management measures in the future. A specific research was carri ed out in 1992 in
    order to investigate the relations between environmental factors and distribution, and the breeding succes. A
    total population of 70-90 breeding pairs was estimated both by direct nest counts (66 breeding pairs) and by
    contemporary counts on the calling adults. A colony (24 nests) was located in the industriaI harbour area,
    while the nests in the urban area (37) can be described as a loose colony. Breeding site features such as
    exposure and roof covering, distance from sea and from nearest nest were surveyed and their distribution
    and effect on breeding were analyzed. Hatching and survival ratio and breeding success were significantly
    higher in the urban area than in the industriaI area colony.

  6. Acari plumicoli nuovi per la Fauna d'Italia (Acari: Sarcoptiformes).


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    17 55

    L’esame di una collezione di Acari plumicoli occasionalmente raccolti in 7 regioni italiane
    (Veneto, Toscana, Lazio, Abruzzo, Molise, Campania, Sardegna) su 31 specie di uccelli in gran parte
    passeriformi (Alauda arvensis, Anthus campestris, Calandrella cinerea brachydactyla, Cettia cettii, Corvus
    corone cornix, Delichon urbica, Emberiza calandra, Erithacus rubecula.Fringilla eoelebs, Garrulus
    glandarius, Hippolais icterina. Lanius senator, Lullula arborea, Monticola solitarius, Parus eaeruleus,
    Passer domesticus italiae, Phoenicurus phoenicurus, Piea piea galliae, Prunella modularis, Sturnus
    vulgaris, Sylvia atricapilla, S. melanocephala, S. sarda, Turdus merula) ma anche piciformi (Dendroeopos
    mediusi, caradriformi (Haematopus ostralegus),gruiformi (Porphyrio porphyrio, Rallus aquaticusi e
    galliformi tPerdix perdix, Phasianus colchicusi, ha consentito di individuare 41 specie di Sarcoptiformes.
    Di esse, una, rinvenuta sull’Usignolo di fiume (Cettia c.cettiii in Sardegna ed appartenente al genere
    Proctophyllodes risulta nuova in letteratura. Altre dieci (Analges bidentatus, A. spiniger, Megniniella obesa,
    Bychovskiata subcharadriii, Pteronyssoides truncatus, Brephoseeles haematopi, Proetophyllodes arcticus,
    P. troncatus, Temnalges mesalgoides, Hirstia chelidonist vengono segnalate per la prima volta in Italia. E’
    probabile che possano essere considerate prime segnalazioni per il Paese anche quelle relative a
    Montesauria rosickji, di cui sono stati osservati esemplari parzialmente mutilati, e a Sokoloviana rehebergi,
    descritta da Canestrini e Berlese (1881) con materiale proveniente dalla Bolivia.

  7. The Dipper  Cinclus cinclus  in Sicily


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    22 66

    The distribution and density of the Dipper (Cincl us cinclus) in Sicily has been studied from
    existing records over the main island’s catchments. The species has been decreasing in number over the past
    40 years and it is now restricted to a few, isolated and residual montane areas and can be considered on the
    verge of extinction. Mean density in these areas (6.3 pairs/lO kms) matches the mean values reported for
    continental Europe, but the decrease in range and the isolation of the populations follow the progressive
    drying and transformation undergone by the Sicilian basins as a result of anthropogenic and rnetereological
    factors. The Dipper’s presence is strongly tied to permanent streams, but its density, assessed by multiple
    regression analysis, is related to stream bed morphology: gradient, substrate granulometry, water
    temperature and depth. The species breeds along stretches of high quality water where, according to the
    E.B.1. method, the fauna is richer in macroinvertebrate than elsewhere.

  8. The foraging behaviour of the Chough  Pyrrhocorax pyrrhocorax in two contrasting habitats


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    17 51

    The foraging behaviour of the Chough Pyrrhocorax pyrrhocorax was compared between Alpine
    and coastal environment at the same time of the year (summer).
    Choughs in both study areas (Aosta valley in northwestern Italy and the isle of Islay in western Scotland)
    took a wide range of arthropods but the diet appeared more diverse in the Alpine area. The Aosta Choughs
    had more variable feeding methods than the Islay ones. Such differences might merely reflect the prey
    species diversity of the two sites, perhaps in turn depending on the environmental diversity. The length of
    stay at any one patch was considerably shorter at Aosta, and this might be related to the lower cost of
    moving in the Alps, by being able to glide along steep slopes. Pecking rates were similar in the two areas,
    although slightly faster at Aosta. Observations carried out on Islay on colour-ringed individuals suggested
    that foraging techniques were age-dependent.

  9. Some aspects of the feeding habits of the Cormorant (Phalacrocorax carbo sinensis)  wintering in the Maremma Natural Park (Grosseto, Centrai Italy).


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    18 61

    The feeding habits of the Cormorant wintering in the Maremma Natural Park have been assessed
    through the analysis of pellets collected in the winter of 1991-92 and 1992-93. In both years the
    quantitative-qualitative analysis of the pellets showed the presence of a rnuch greater percentage of Mullets
    (Mugilidae) than of other fishes: 60% in nurnber and 90% by weight; the mean size of the fish was 21.5 cm.
    The rnean fish weight ingested daily, estirnated from the pellet contents, was 278 g in 1991-92 and 377 g in

  10. Fledging rate in the Cormorant  Phalacrocorax carbo at the colony of Val Campotto (Po Delta, N-E Italy)

    Grieco F.

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    20 44

    Cormorants Phalacrocorax carbo nesting at the Val Campotto colony occupied 270 nests in
    1993. In 1992 and 1993, the number of f1edglings from 190 successful broods was recorded. Each brood
    was assigned to one of 3 laying periods defined within the breeding season (February-March, April-early
    May, late May-July), The mean number of f1edglings per nest was 2.81 ± 0.08 (SE) in 1992 and 2.80 ± 0.06
    (SE) in 1993. In 1993 the fledgling production in late broods was lower than in early ones; no difference
    was found between nests at the centre and those at the edge of the colony, nor among cJusters of trees of
    different density. o cases of predation were observed. Data indicate a further growth of the colony. Some
    second brood attempts are also reported.

  11. Does prey size affect predatorybehaviour of Kestrel ?


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    19 40

    sample of IO rehabilitated kestrels Falco tinnunculus was tested immediately prior to release
    to ascertain whether their predatory behaviour was modified according to the type of prey the kestrel faced.
    The tests were carri ed out individually in captivity conditions, using either one laboratory agouti mouse
    weighing 12-15 g or one laboratory agouti rat weighing 48-60 g. The size ratio between the prey was then
    constantly of 1:4.
    The behavior displayed by the kestrels before either prey was c1early different, both prior to and after its
    catching. The rat elicited more conflict patterns, such as preening and movements on the perch, while this
    was hardly ever record ed during the rnouse-tests. There were instead no differences in the latency of
    predation and the technique used for grasping the prey. In contrast, the rat received more biting than the
    mouse, and the latency of ingestion, interpreted as the time span necessary to induce the death of the prey,
    was much longer when the rat was captured. The adaptive implication of such behaviour differences are

  12. Egg size variability between clutchesof Choughs  (Pyrrhocorax pyrrhocorax)

    TELLA, J.L., JOVER, LL. and RUIZ, X.

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    12 58

    The main sources of egg-size variability al interclutch level (clutch size and female) have been
    analyzed for 57 pairs of Choughs breeding at the Ebro Valley (Monegros) area in 1992. Egg-size variability
    is not affected by clutch size variation (4,5 and 6 eggs), whereas it is influenced by female characteristics.
    These results are discussed in relation to the findings in other birds, particularly Corvidae, and a final
    hypothesis, taking into account the existence of sexual dimorphism and courtship feeding behaviour in these
    birds, is emitted to explain them.

  13. Flight strategies of Honey Buzzards during spring migration across the Central Mediterranean


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    21 49
  14. Inter-annual constancy in the laying period or Cory's Shearwater  Calonectris diomedea diomedea on Lavezzi Island (Corsica)


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    12 61
  15. Status and habitat use of a populationof Great Bustard in southern Spain.


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    14 54
  16. Book reviews

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    14 50