Volume 20 - N. 2
December 1996

Avocetta
Volume 20 - N. 2



  1. Avocetta n. 20 (2) - 1996

    Abstract     Read Article       Download
    29 97
  2. Effects of environmental conditions on aerial feeding by Collared Pratincoles Glareola pratincola breeding in southwest Spain

    CALVO B, FURNESS R. W.

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    23 52

    During the chick-rearing period, adult Collared Pratincoles Glareola pratincola tended to feed
    in the colony or nearby on insects caught in flight. Before and after this period, they often moved further
    from colonies to forage in groups over areas of marshes and reeds. Daily activity was highly influenccd.by
    weather conditions. Collared Pratincole feeding density was lower on rainy, windy or cloudy or cloudy
    days. [n generai, fccding activity increased through the morning up to early afternoon and decreased after
    that. Food availability in marsh and reed sites was higher than in the crop site. Apart frorn cereals, few
    Collared Pratineoles fed over crops.

  3. Distribution status and breeding of the White Stork Ciconia Ciconia in Greece

    TSACHALlDISl E., PAPAGEORGIOU N.

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    36 59

    Two thousand three hundred and eighty seven nests (2387) of White Storks Ciconio ciconio were
    found in Greece during the Summer of 1993, Here are presented the geographical distribution and breeding
    success ofthe species. The average population density (StD) was found to be 8.4 pairs per 100 Km’, ranging
    from 46,05 to 0,09 pairs per 100 Km2 The average nurnber of fledged young per nest (1Zm) was 2,87,
    ranging from2,3 to 5,0, The highest nest was found at an altitude of 940 m a.s.l. while the majority ofthe
    nests (76%) were found at an elevation <100 m a.s.l, The White Stork prefers as nesting sites electrical poles, both with platform (artificial nests) (53.5%) and without platform (18%). Wetland areas seems to play the 1110stimportant role affecting the density and geographical distribution of the species. The lack of suitable nesting sites appear to be the criticai limiting factor for the species population size.

  4. Extension of post-juvenile moult and ageing of the Cetti's warbler Cettia cetti  in northern Italy

    PILASTRO A., TASINAZZO S. and GUZZON C.

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    35 109

    The extent of the post-juvenile moult of Cetti’s warbler was studied in northern Italy. Compared
    to previous studies, it was found to be more extended than in northem Europe populations, involving body feathers
    and most of wing coverts. Moreover, juvenile birds moulted rather frequently all the tertials and up to 5 inner
    secondaries. In 6 cases out of 102 examined (4.9%), also 2-5 primaries were moulted. Birds frorn first clutches
    moulted significantly more greater coverts than birds from second clutches. Extension ofthe post-juvenile moult
    was significantly correlated with the degree of skull pneumatisation in September and October, suggesting that
    birds from early clutches have a more extended moult. Moreover, males moulted on average significantly
    more remiges and greater coverts than females. Moult limit. i.e. the contrast between moulted adult-like
    feathers and unmoulted juvenile feathers. was visible in all examined juvenile birds within greater coverts or,
    altematively, within tertials or secondaries. Pre-nuptial moult was restricted both in terms ofindividuals and
    number offeathers involved, and never affected wing coverts or remiges. On the basis ofthese results, a new
    method for ageing Cetti’s warbler, based on the contrast between moulted and unmoulted feathers, is proposed.
    This method allows juveniles to be told apart from adults beyond the completion of skull pneumatisation,
    until their first complete moult.

  5. Arthropod abundance and breeding performance of Tits in deciduous,evergreen oakwoods and pine reafforestation of Sicily (Italy)

    Massa B., Lo Valvo F.

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    24 53

    The aims of this research, carried out in 1993-96, were: l) to ascertain the existence of
    differences in resource abundance between deciduous and evergreen oakwoods; 2) to verify the overlap
    degree of the peak resource and the peak-demand of young Tits in the two oakwoods; 3) to study the
    breeding performance ofTits (Parus major and P. caeruleus) in relation to resource parameters in woodlots
    dominated by trees of different species which are part of the same woodland, namely evergreen Quercus
    ilex, deciduous Quercus pubescens and Pinus halepensis reafforestation. In the four years of this research
    clutch size, number of fledglings and arthropod abundance were higher in the oakwoods than in the pine
    reafforestation; the arthropod abundance coincided with the peak of demand by young, particularly in
    deciduous oakwood. Blue and Great Tits breeding in oakwoods appeared to be significantly more successful
    than in reafforestation sites; clutches generally were larger and started earlier in the oakwoods than in
    reafforestation. Even if differences in the arthropod abundance between deciduous and evergreen oakwoods
    were detected, no important differences in the breeding performance were noticed in the four years, while
    they were observed in the pine reafforestation in respect to oakwoods, both for Great and Blue Tit.

  6. Changes in density distribution of the Hooded Crow Corvus corone cornix  and the Magpie Pica pica  in Northern Italy

    FASOLA M., CACCIAVILLANI S., MOVALLI C. AND VIGORITA V.

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    35 52

    We describe the density distribution ofbreeding Hooded Crows and Magpies over 12,827 km of planitial landscape,
    and we quantify the changes that have occurred since 1980. Nest were censused by
    means of winter roadside counts. We tested this technique by applying it to 12 sample zones where the
    breeding pairs had been censused during the preceding reproductive season, and we caIculated a conversion
    index from winter nest counts to breeding densities. The breeding populations for the entire study area in
    1994 increased by 107% of the 1980 population for the Hooded CTOWand by 27% for the Magpie.
    Compared to 1980, the areas with high density of Hooded Crows in 1994 expanded north- and east-ward,
    while the distribution of the Magpie was similar to that in 1980. The density distributions of both corvids
    showed a clear structure with centers of abundance and with concentric bands of decreasing abundance, a
    pattern probably determined by gradients of environmental factors. However, the planitiallandscape of our
    study area is very uniform, and there is no noticeable gradient to match the density variations between the
    two corvids; the variations therefore remain unexplained. The 1980 distribution patterns had suggested that
    predation or competition by Hooded Crows could limit Magpie distribution at a geographic scale, but the
    1994 data do not confirm this hypothesis.

  7. Food of Italian Sparrow Passer italiae nestlings in CentraI ltaIy

    MONDINO L., FRATICELLI F. and CONSIGLIO C.

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    37 71

    The diet of Passer italiae nestlings was studied in a wood of Centrai Italy. All samples
    contained arthropods, and shell fragments, seeds and gravel were also abundant. Diet diversity changed
    with age, being max imum at about 8 days of age. Diversity also increased with the number of nestlings.
    Differences were found with diet of nestlings of Passer domesticus and Passer montanus. Predation on
    eggs and nestlings was high.

  8. Feeding success and relationships of some species ofwaterbirds in the «Valli di Comacchio» (ltaly)

    BIDDAU L.

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    19 50

    The feeding success of Black-headed gull, Cornrnon tern and Little egret was studicd in the
    \”Valli di Comacchio\” lagoon (northeastern Italy), both in presence and abscnce of intra and interspecific
    interactions. Sometimes gulls and terns feed on the same areas and on particular occasions aggregate with
    other waterbirds, but little is known about the fccding success and behavioural interactions among thern.
    The aim of this work was to evaluate the interactions and the feeding success of gulls and terns foraging
    sintopically with Little egrets. The Little egret had a very high feeding success, but the intraspecific
    territorialism strongly reduced the time available to fish. The Cornmon tern had difficultics to dive because
    of the presence of Black-headed gull swimming in the water. The gull was equally successful both in
    presence and absence of intra and interspecific competition. Then, the observed feeding rate were highcr
    than data frorn literature; this let to suppose that the birds were attracted by a favourable food supply. I
    suggest that the observed species are independently attracted to a rich food source.

  9. Passerine birds preyed by the four-lined snake Elaphe quatuorlineata: some remarks on the predatory tactic and the relevance of avian prey for reproductive female snakes

    ANGELlCI F.M., FILlPPI E., LUISELLI L.

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    24 82
  10. Shell size relationships in the consumption of gastropods by migrant Song Thrushes Turdus philomelos

    GONZALEZ-SOLIS J., ABELLA, J. C. and AYMI R.

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    24 94
  11. Birds in the diet of the Barn Owl (Tyto alba)in an agricultural habitat of northern Italy

    GUIDALI F. and PIGOZZI G.

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    21 76
  12. Great Reed Warblers Acrocephalus arundinaceus arundinaceus performing complete remex moult before post-breeding migration

    MAGNANI A. and SERRA L.

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    16 39
  13. Dati sulle patologie dei Rapaci in Sicilia

    Siracusa A.M.

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    21 60
  14. Reproductive parameters and nestling growth in Hoopoe  Upupa epops  in an area of CentraI ItaIy

    BALDI G., SORACE A.

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    23 62
  15. Book reviews

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    19 34