Volume 18 - N. 2
December 1994

Volume 18 - N. 2

  1. Avocetta n.18 (2) - 1994

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    22 326
  2. The diet of the Chough  Pyrrhocorax pyrrhocoraxas indicated by analysis of  digested prey remains


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    60 455

    The largely invertebrate food of Red-billed Choughs, Pyrrhocorax pyrrhocorax, living on the
    mariti me cliffs and hinterland ofWest Wales and Cornwall was investigated by analysis ofprey remains in
    pellet and faecal samples. Undigested material was identified to varying taxonomic levels dependent upon
    the degree offragmentation and the skeletal units recovered. This was carried out as part ofa study aimed at
    conserving the species at the southern edge of its British range, and assessing the feasibility of reestablishment
    in Cornwall.
    Direct observation showed that, in the breeding season, ants were a major resource, but their absence from
    faecal samples suggested that they are fed exclusively to nestlings. Otherwise, beetles and dipterous larvae,
    especially tipulids, were predominant foods. The majority ofthe prey identified in this study are associated
    with well-grazed rough pasture and maritime cliffs. Dung fauna apparently guarantees a food supply through
    lean periods. The importance of earthworms is ambiguous: direct observation and faecal evidence suggest it
    was a regular and important source ofwinter protein, possibly when cerea l grain was unavailable.

  3. Distribution and  population-size of colonies of Yellow-Iegged Gull  Larus cachinnans michahellis breeding in North-Eastern Adriatic sea


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    23 47

    The distribution of colonies of Larus cachinnans michohellis in the North Adriatic is related to
    the vegetation and the presence/absence of human interference. Strong increases in recent years are noted
    and an estimate for the Northern Adriatic population (40,000 – 50,000 pairs) is given.

  4. Winter sympatry of two Reed bunting  (Emberiza schoeniclus) subspecies in  the Venetian lagoon


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    32 67

    Morphometric data were taken on 403 specimens of Reed bunting, mist-netted during a 7 year
    peri od on the northern border ofthe Venetian lagoon. Two morphs could be clearly identified on the basis of
    bili depht and wing lenght. The large-billed, short-winged morph (E. schoeniclus intermedia) was caught year
    round, while the other (E. schoeniclus schoeniclus) was caught only from October to March. The distributions
    ofbill depth ofthe two morphs showed some overlap that may suggest hybridization: birds of intermediate bili
    size, however, were never caught in summer months and their wing lenght was that of E. S. schoeniclus.

  5. Some comparative aspects of the breeding biology of Black-headed Gull (Larus ridibundus), Common Tern (Sterna hirundo) and LittleTern (Sterna albifrons) in the Lagoon of Venice, NE Italy


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    20 49

    During the years 1989-1992 three species of Laridae and Sternidae breeding in the lagoon of
    Venice were studied. The breeding population of L. ridibundus increased steadily through the period of
    study, whereas S. hirundo was stable and S. albifrons decreased. Alrnost ali of the colonies were closely
    clustered in the southern lagoon, where hurnan disturbance is less heavy. Colonies were located on a few of
    the apparently favourable sites. Colony size was significantly higher in S. hirundo (90.8 ± 80.1, n=45) than
    in S. albifrons (51.9 ± 72.3, n= 12) and in L. ridibundus (26.3 ± 42.5, n=20). S. hirundo was significantly
    associated with L. ridibundus, whereas S. albifrons avoided the occurrence ofthe latter species. Site tenacity
    did not differ arnong species, with the rnajority of sites being occupied only for one or two years.
    Suggestions for the protection ofthe colonies are proposed.

  6. Su una collezione di Mallofagi dei Caradriformi: 8 taxanuovi per l'Italia e review delle specie


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    22 66

    Da 41 esemplari di uccelli appartenenti a 22 specie di Caradriformi, di cui 19 osservate in Italia
    e 3 in Somalia, sono stati raccolti 99 esemplari di Mallophaga riconducibili a 23 specie (5 Amblycera, 18
    Ischnocera), di cui almeno 8 risultano essere nuove per la fauna d’Italia: Actornithophilus pustulosus (Piaget
    1880), A. tafani (Schrank 1803), A. umbrinus (Burmeister 1838), Carduiceps meinertzhageni Timmermann
    1954, Cummingsiella ovalis (Scopoli 1763), Koeniginirmus eugrammicus (Burmeister 1838), Quadraceps
    fissus (Burrneister 1838), Q. similis (Giebel 1866).

  7. Dependence of Yellow-Iegged Gulls (Larus cachinnans) on food from human activity in two Western Mediterranean colonies

    BOSCHI M., ORO D. and RUIZ X.

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    24 74

    The diet of tledging chicks of the Yellow-Iegged Gull (Larus cachinnans) was studied in the
    Medes Islands and the Ebro Delta, two Northwestern Mediterranean colonies with differing ecological characteristics.
    The diet ofthe Medes Islands colony showed a higher biomass percentage oftip food than from
    the Ebro Delta colony. At the Ebro Delta, chicks consumed a higher biomass percentage ofpreys from channel
    s, mainly mullets (Mugil sp.) and showed a higher foraging niche width. The consumption of garbage
    from refuse tips seems to affect the growth patterns in both populations.

  8. The breeding biology of Dupont's Lark,Chersophilus duponti, in Europe

    Herranz J., Manrique J., . Yanes M. and Suarez F.

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    26 127

    Very little published information exists concerning the reproductive biology of Dupont’s Lark,
    Chersophilus duponti, and what is available largely refers to the North African population. Here we present
    data frorn 33 nests found in southeastern (n= 15) and centraI (n= 16) Spain between 1989 and 1993.
    The reproductive period extended frorn mid March lo early July, a month longer than the orth African
    populations. The laying peri od in SE Spain started more than a monrh earlier than in centraI Spain. Nests
    were placed on the ground, nearly always partially covered by shrubs (88 %), and oriented to the W, or
    E (84%) of the closest plant. In SE Spain, this species appears to select nest site positions covered by
    shrubs 7-12 cm in height. o selection was evident in centraI Spain, where shrub height rnay be closer IO the
    optirnurn required. Mean clutch size (3.6±0.6 sd) was larger than that reported for North Africa, but no
    differences were found between the two areas in Spain. lndications ofasynchronous hatching were found,
    and appear to depend on clutch size. Mean egg length and width were 0.5 mrn greater than those reported
    previously. The incubation peri od was 12-13 days. Nestling period was very short (8 days). est mortality
    was extremely high (84%), but egg hatchability was high (95.7%), and no nestlings starved (n=32).
    Coleopteran and lepidopteran larvae forrn 50%. of nestling diet, bui araneids (especially Lycosidae) are
    particularly important early in the nestling periodo

  9. Maladaptive adoptions in the Hooded Crow Corvus corone cornix


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    21 61

    Three cases of post fledging adoption were observed in 13 nests located in a northern ltalian
    study area, where Hooded Crows nest at a high density (6.7 nests per km\”), Adoptions occurred imrnediately
    after fledging; any later atternpt ofyoung to obtain food frorn adults other than own parents was unsuccessful.
    Feeding frequency was not different between adopted young and true offspring. Feeding performance
    before tledging did not di ffcr bctween the pairs frorn which the adopted young originated and those that
    becarne foster parents. lt is presurned that Hooded crows lack the ability to recognize their offspring and
    adoptions are a maladaptivc phenornenon due to the high nesting density.

  10. Wasteland bird use. Evidence from the NW Mediterranean coast (Genoa, Italy)


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    20 51

    Bird occurrence was recorded from January 1989 to June 1991 in a wasteland area located on a
    sea embankment within a dammed sea basin close to the city of Genoa. The study area was visited almost
    weekly, globally recording 173 species whose occurrence ranged from a few to more than one thousand individuals
    at a time. Regularly detected species showed seasonal occurrence or seasonal fluctuations in numbers
    of individuals. Bird communities also showed seasonal turnover as testified by the cyclic trend ofthe
    herbivores/carnivores ratio. A description ofthe year succession ofbird communities was achieved by correspondence
    analysis between months and a total of69 most common species. The first axis (37.6% ofinertia)
    displayed species typical of different seasons, while the second one (22% of inertia) was related to the
    transient occurrence of migrant species. The most complex bird community was that of wintering species,
    mainly divided into sea birds and a crowded group of passeri ne species, whereas the warm season cornrnunity
    was less defined, excluding the Ringed Plover and the Short-toed Lark which bred in the area.
    Additionally, the area was also used as a refuelling ground by many migrant species, especially wetland
    birds when it was flooded by rain. Based on these data, and considering natural environment dcpletion, the
    value of wasteland as wildlife habitat and the opportunity of planning the occurrence of low-disturbance
    plots within heavily urbanized areas is discussed.

  11. Prima nidificazione di Lanario Falco biarmicus in provincia di Siena e note sulla locale distribuzione storica


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    29 84
  12. Book reviews

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    19 56