Volume 15 - N. 1/2
1/2 1991

Avocetta
Volume 15 - N. 1/2



  1. Avocetta n.15 (1-2) - 1991

    Abstract     Read Article       Download
    13 90
  2. Niche organization of a forest bird community in north-western Italy during autumn and winter. A comparative analysis

    ROLANDO A. and TECCHIATI F.

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    12 33

    The niche organization of a deciduous forest bird community (Passeriformes and Piciformes)
    in north-western Italy has been described by considering other activities in addition to foraging.
    Principal Component Analysis suggests that, with regard to foraging, the first factor (PCl) depends
    on the use of outer parts of branches and middle height of trees in autumn whereas it is mainly concerned
    with the use of trunk , ash and oak versus the ground in winter. As for singing , the first factor
    is highly correlated only with particular species of trees in autumn whereas it defines the use of the
    outermost parts of branches in winter. Such differences reflect well-known seasonal shifts in the behaviour
    of species. The lack of correlation between foraging and singing rotated loadings suggests that
    foraging community organization differs from the singing one.
    Cluster analysis (Pearson’s distance) stresses the ecoiogicai isolation of woodpeckers both in autumn
    and in winter. Also tits and associated species are seen to be separate enough from others both in
    foraging and in singing. Dendrograms computed on data collected without distinguishing birds’ activities
    are more similar to foraging dendrograms than to singing ones. This seems to suggest that in
    autumn and winter community organization is more dependent on foraging than on singing activities.
    Since the results of the Cluster analysis are in agreement with those previously obtained concerning
    the same data but worked out by simple niche overlap indices, it may be inferred that both methods
    of data analysis are adequate to describe community organization.

  3. Some aspects of the spring migration of the Willow Warbler Phylloscopus trochilus, on the isle of Capri

    BEZZl E.M. and GUSTlN M

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    10 49

    Some aspects of the migration of the Willow Warbler Phy/loscopus trochilus were studied
    on the isle of Capri in the spring of 1987. 309 individuals were captured between ApriI 13th and May
    24th. 200 m of nets were used in groups of 20-30 m each within an area covering approx. l hectare
    and made up of Mediterranean bush. The trend of the capture, which was concentrated in the second
    half of the month of ApriI, did not appear to be determined simply by the different transit of males
    and females in the species but also by groups of different individuals. In the nominaI ssp. 2 different
    groups of individuals were distinguished, one characterized by colour note 2, the other by colour notes
    3 and 4, according to the amount of yellow streaks on the breast and belly. The study examines the
    rnigratory transit and differences in fatty deposits between males and females in the three groups.
    The ssp. acredula, which is distinguished by wing length, appears different from the nominaI ssp. also
    in the transit periodo

  4. Italian Sparrows (Passer italiae) breeding in black kite(Milvus migrans) nests

    PETRETTI F.

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    9 38

    ltalian Sparrows were found breeding in Black Kite nests in a woodland in Centralltaly.
    The sparrows usually bred only in active raptor nests and their reproductive cycle seemed to be
    synchronized with that of the kites, the highest number of sparrow broods occurring when the raptor
    nests were occupied by the chicks. The adult sparrows were seen feeding in the raptor platforms when
    adult kites were away.

  5. Chick mortality and hatching asynchrony in the Pallid Swift    Apus pallidus

    MALACARNE G. and CUCCO M.

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    9 37

    In swifts (Apodiformes), hatching asynchrony has been frequently reported and it has
    been suggested (Lack, 1947) that it can enhance reproductive success because in favourable conditions
    an extra chick can be reared, while in poor conditions it can be eliminated (brood reduction hypothesis).
    In this paper hatching asynchrony is studied in relation to nestling mortaIity.
    A four year study of the Pallid Swift in two Piedmontese (NW Italy) colonies has been conducted.
    Clutch size and other measures of reproductive success were record ed in 313 nests, either of the first
    or of the second c1utch.
    Hatching success and f1edging success were similar to those observed in previous years in the same
    North-Italy area. Mortality increased, both in the first and second brood, in late-laid c1utches. Chicks
    died mainly during the first ten days after hatching.
    The most important factor affecting nestling surviva1 was hatching hierarchy: the last hatched, especially
    in three-egg c1utches, experienced higher mortality. Hatching asynchrony was nearly always observed
    in three-chick broods, and in 751110 of the cases in two-chicks broods. In the latter situation, asynchronous
    and synchronous broods did not differ significantly as to mortality and mass of the f1edging birds.
    It is discussed why in two-chick broods hatchìng asynchrony did not affect strongly the breeding success,
    while in three-chick broods the survival value of asynchrony was apparently fully expressed.

  6. Studio sull'alimentazione della popolazione di Storni svernante nella città di Roma

    Fortuna P.

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    10 34

    Attraverso l’analisi degli escrementi è stata studiata l’alimentazione della popolazione
    di Storni (Sturnus vulgaris) svernante nella città di Roma negli anni 1985-1987. La dieta comprende
    19 categorie sistematiche di prede animali (Artropodi e Molluschi Gasteropodi terrestri) e 20 specie
    vegetali. In base alle prede identificate, gli ambienti principali di alimentazione appaiono rappresentati
    da prati incolti, macchia aperta, oliveti e vigneti.

  7. Il Picchio rosso maggiore (Picoides major L.) nella limitazione naturale delle popolazioni della Saperda maggiore del pioppo (Saperda carcharias L.)

    ALLEGRO G.

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    12 44

    Negli anni 1988/90 è stato realizzato uno studio sull’importanza della predazione del
    Picchio rosso maggiore verso la Saperda maggiore, pericoloso parassita xilofago del pioppo. L’analisi
    delle “life tables” dell’insetto ha evidenziato che il principale fattore di mortalità è rappresentato dalla
    reazione dei tessuti corticali della pianta, che è in grado di eliminare fino all’800Jo delle uova e delle
    giovani larve. Non è tuttavia trascurabile l’azione del Picchio rosso maggiore, che preda le larve del
    parassita durante l’inverno, distruggendo nei casi più favorevoli oltre il 50% della popolazione larvale
    svernante.
    In base ai dati raccolti in 28 pioppeti padani la predazione appare più elevata nei pioppeti adulti e
    confinanti con aree di bosco naturale rispetto ai pioppeti più giovani e isolati. Esiste inoltre una correlazione
    positiva tra l’entità della predazione e la presenza di cavità-nido o dormitorio scavate dal picchio,
    e, almeno per i pioppeti golenali, tra il primo fattore e la densità di popolazione della Saperda.
    L’evidenza di una risposta funzionale del predatore consente interessanti ipotesi sul ruolo del Picchio
    rosso maggiore nella limitazione naturale delle popolazioni di Saperda carcharias.

  8. Date of laying, clutch size and second brood percentage in Great Tit Parus major and Blue Tit Parus caeruleusin the Natural Reserve "Monte Rufeno" (VT, Centrai Italy)

    BELLAVITA M. & SORACE A.

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    10 58

    The breeding biology of Great Tit and Blue Tit has been studied in the natural reserve
    “Monte Rufeno”. For both species, compared to other European areas, an earlier laying date, a smaller
    clutch size and a higher percentage of second clutches were observed. These results are discussed.

  9. Densità e distribuzione del Falco di palude, Circus aeruginosus,in Toscana

    LIBERATORI F., PENTERIANI V. & PINCHERA F.

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    10 86
  10. Censimento dell' avifauna nidificante in un saliceto ripariale

    Montanari P.

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    11 45

    Mediante il metodo del mappaggio ho censito l’avifauna nidificante in un saliceto ripari aIe
    del fiume Po. In totale ho rilevato la presenza di 20 specie e una densità totale di 54,4 coppie per
    IO ha; l’Usignolo Luscinia megarhynchos risulta la specie più abbondante. Le ridotte dimensioni dell’area
    in esame influenzano negativamente la struttura della comunità nidificante che tuttavia presenta specie
    di interesse biogeografico locale.

  11. The annual presence of the gannet (Sula bassana) in the central Thyrrenian Sea

    BERNONI M., CARERE C., GUSTIN M.

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    11 33

    Observations for a total of 249 hours were made on the Thyrrenian coast by the mouths
    of Tevere river from December 1983 to Aprii 1985. The regular presence of the Gannet was recorded
    and confirmed both in wintering and migratory periods; the presence of mainly adult individuals in
    these waters suggests that immatures migrate tow.ards eastern seas. On the whole, a distinct prevalence
    of single individuals (1.59 ind./obs.) was noticed even during migratory periods.

  12. Short communications

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    31 31
  13. Book reviews

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    18 62