Volume 26 - N. 1
June 2002

Avocetta
Volume 26 - N. 1



  1. Avocetta n.26 (1) - 2002

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    22 42
  2. The corncrake (Crex crex) in Friuli Venezia Giulia (North eastern Italy)

    Rassati G. & Tout C. P.

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    20 66

    The following article is a summary of the current levels of knowledge available for the Corncrake in the region Friuli-Venezia Giulia, especially with regard to studies carried out from the middle of the 1980’s onwards.
This rail species has been the subject of continuous study since the end of the 1980’s in certain sample areas of Upper Friuli both through the collection of general data and, from 1993 onwards, breeding censuses carried out at least twice in each nesting season. During the 1995 nesting season a breeding survey was carried out covering the entire territory of the Region.
The studies have enabled us to establish that in Friuli-Venezia Giulia the species is a regular migrant and nesting species that is occasionaly present even in the autumn and winter when one occasionally encounters individuals that for various reasons (injuries, handicaps or disease) are unable to migrate.
The regional population censussed in 1995 yielded 203 calling males largely located in the central-north part of the region at an altitude between 100m a.s.l. and 1600m a.s.l. (68,8% of the calling males were found between 500m a.s.l.1999 m a.s.l.). In Upper Friuli, for the period 1993-1999, the majority of the calling (5 1 .3%) were located between 200m a.s.l.
The bird is almost completely absent below 200m a.s.l. as a result of the high levels of human impact on the environment and the subsequent absence of suitable habitats for the species. The increasing rarity of the species above 11 00m a.s.l. is due to the lack of broad valley bottoms and human settlements with their regularly cut hay meadows. The upper altitudinal limit for the species is determined by the disappearance of grassland habitats which are replaced by krummholz scrub, screes and bare rock.
The environment favoured by the species in Friuli-Venezia Giulia seems to consist of relatively humid hay meadows with good vegetational cover which are regularly cut in areas with at most a slight slope.
The authors hope that concrete protection measures for the species will be taken with regular monitoring over the years with a view to gathering information on the habitats used by the birds so that appropriate conservation projects can be undertaken.

  3. Age-dependant adult survival in the Cory's Shearwater (Calonectris diomedea)

    Mougin J.L., Jouanin C. & Roux F.

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    17 37

    In the Cory’s Shearwater Calonectris diomedea of Selvagem Grande (30°09’N, 15°52’W), the annual survival rate of the adult is age-dependant. After having remained almost constant during the first breeding years, it begins to decrease shortly after the 15th when the bird has not much passed its 25th year. Such a trend having also been observed in other seabird groups, it is likely to be widespread. The scarcity of the related data published is thus likely to be only a consequence of the length of the studies necessary to get them.

  4. Distribution patterns of snow finches (genus Montifringilla) in the Tibetan Plateau of China

    Yan Hua, Fu Min, Zuo Hua & De Ritis

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    15 47

    We used data from specimen collection records and field expeditions in the Tibetan Plateau and Xinjiang to assess distribution patterns of six Montifringilla species. By plotting specimen localities with latitude, longitude and elevation, we found that six species overlap greatly on the Tibetan plateau, with a limited distributed area at elevations from about 2500m to 5500m, latitudes from about N26o to N38° and longitude from E 751 to EI 151. At 28 of 71 localities, more than one species has been collected. However, in Xinjiang, only four species occur and they have parapatric complementary distributions. The species whose distribution ranges overlap occur in different habitats and develop different ecological and behavioral characteristics. While some breed and roost in rock crevices, others nest in Pikas (Ochotona curzoniae, Ochotona ladacensis, Ochotona alpina, Ochotona daurica) burrows. Those species sharing similar habitats show significant variations in body traits. It seems that the species with similar body traits are less likely to share similar habitats than are species with rather different body traits.

  5. Spring migration of raptors on Conero promontory

    GUSTIN M., SORACE A., Ardizzone D. & Borioni M.

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    17 70

    A survey of raptor migration on the Conero promontory was carried out during spring 1999 (April 20 – May 20), in which the time of passage, and the direction of both in-coming and out-going flights were recorded. Some 2640 migrating raptors were observed, mostly Honey Buzzards (1699 individuals) and Marsh Harriers (503 individuals), altogether representing about 83.4% of total observations. In-coming flight direction was mostly WSW and WNW, while the direction of out-going flights was mainly ENE and ESE. Significantly more individuals were observed passing in the afternoon (15-1800). In addition, the present study, reveals an increase in the number of raptors observed (about 40% more) migrating over the study site compared to a similar survey carried out in spring 1994. The number of raptors observed in the present study being second only to the number of raptors recently observed migrating over the Straits of Messina. Together, our results confirm the importance of the Conero promontory as a site for raptor spring migration.

  6. Nesting and Feeding Habits of the European Bee-eater (Merops apiaster L.) in a Colony next to a Beekeeping Site

    Massa B. & Rizzo M.C.

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    40 100

    Authors carried out a study on a population of bee-caters colonising a former sand quarry next to a beekeeping site. Data were collected to estimate population size, evaluate microclimate differences inside and outside nest tunnels, calculate bill length and weight variation in relation to nest excavation and nest attendance by bee-eaters, and to analyse their feeding habits, in particular in relation to bee availability. Population size was estimated as much as 100-110 pairs. Bill length resulted to decrease during the nest excavation, growing again after one month. Weight on the contrary was increasing during egg laying and brooding, and decreasing during nestlings’ attendance. Temperature outside nests resulted on average lower than inside the nest tunnel, which in turn resulted much more constant. Bee-eaters are specialized in hymenopterans predation, and considered in some countries a pest for beekeeping. The analysis of the relationships between availability of bees and bees preyed upon by be te . the study area consented to consider bee predation incidence actually acceptable to the bee colony for future survival.

  7. Note sulla biologia riproduttiva del Cannareccione Acrocephalus arundinaceus in zone umide dell’Italia Centrale

    Quaglierini A.

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    19 47

    During nine years, a study was carried out on the nesting population of Acrocephalus arundinaceus in a large marsh of fresh water and in the small artificial wetland of Central Italy. Data about location of nest and main reproductive parameters were collected with the main purpose of analysing Great Reed Warbler habitat relationships in an attemp to clearify the reasons for numerical reduction of the species from 1992 on. Nest is averagely hanged up in five stems, 91 em from water height and 78 em far from open waters. Under the nest, water is averagely deep 51 em and reed density is of 497 stems/mq For anchorage, 238 em stems high are used each of which is 0,56 em diameter. Eggs are lightly smaller than other italian and european ones. Similarly, compared with literature, the average of a complete clutch – 4,39 eggs – is inferior of 78%. Informations confirmed regular accomplishment of two broods. First brood between april 29 th and june 6 th, second one between june 10th and july 28th, with various episodes of sostitutive first brood. Hatch rate was 77,8%; 90,2% of nestlings have left nest (at least 2,78 each nest are youngs); the total reproductive outcome has thus resulted of 70,2%. 25,7% of builted nests have been plundered or abandoned or parasited by Cuculus canorus. The Great Reed Warbler for reproduction uses different types of reeds and it doesn’t seem to be influenced by Abstract – During nine years, a study was carried out on the nesting population of Acrocephalus arundinaceus in a large marsh of fresh water and in the small artificial wetland of Central Italy. Data about location of nest and main reproductive parameters were collected with the main purpose of analysing Great Reed Warbler habitat relationships in an attemp to clearify the reasons for numerical reduction of the species from 1992 on. Nest is averagely hanged up in five stems, 91 em from water height and 78 em far from open waters. Under the nest, water is averagely deep 51 em and reed density is of 497 stems/mq For anchorage, 238 em stems high are used each of which is 0,56 em diameter. Eggs are lightly smaller than other italian and european ones. Similarly, compared with literature, the average of a complete clutch – 4,39 eggs – is inferior of 78%. Informations confirmed regular accomplishment of two broods. First brood between april 29 th and june 6 th, second one between june 10th and july 28th, with various episodes of sostitutive first brood. Hatch rate was 77,8%; 90,2% of nestlings have left nest (at least 2,78 each nest are youngs); the total reproductive outcome has thus resulted of 70,2%. 25,7% of builted nests have been plundered or abandoned or parasited by Cuculus canorus. The Great Reed Warbler for reproduction uses different types of reeds and it doesn’t seem to be influenced by any specific parameter. The recent increase of water level in Massaciuccoli – with the consequent delayed growth of reeds seems to have a negative influence on the territorial occupation phase for what concerns males.

  8. Water-crossing tendency of juvenile Honey Buzzards  Pernis apivorus during migration

    AGOSTINI N., COLEIRO C., CORBI F., DI LIET0 G., PINOS F. & PANUCCIO M.

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    18 106

    The autumn migration of juvenile Honey Buzzards was studied from 15 to 29 September 2000 at three sites of the central Mediterranean: the Circeo promontory (central Italy) and the islands of Marettimo (western Sicily) and Malta. The aim of this study was to test the hypothesis that juvenile Honey Buzzards leaving the Italian peninsula from the Circeo promontory, reach Tunisia via the island of Marettimo. At the Circeo promontory a total of 500 individuals was counted with the peak on 21 and 22 September. Juvenile buzzards showed a strong tendency to undertake the sea crossing flying south apparently towards western Sicily via the island of Ponza. 13 birds were seen flying back inland. On average flocks contained 4.8 birds and only one, observed on 21 September, contained more than 20 individuals (87). Over the island of Malta 564 Honey Buzzards were counted with a maximum of 279 on 23 September. There was a notable correspondence between data recorded in these two sites, both concerning the variations of the migratory flow and the size of flocks. Over Marettimo, a total of 45 buzzards were seen in the whole period. These results do not agree with the hypothesis tested in this study; on the contrary they seem to suggest that birds avoid the crossing of the Tyrrhenian Sea deviating east towards the Italian peninsula and passing over Malta about two days later.

  9. Nest site and Breeding Biology of the red-footed falcon (Falco vespertinus) in northern Italy

    SPONZA S., LICHERI D., GRASSI L.

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    17 82

    Una popolazione di Falco cuculo di sette coppie nel 1997 e di quattro nel 1998 si è stabilita nella pianura padana, in provincia di Parma. Le coppie hanno utilizzato nidi di Cornacchia grigia, posti su alberi di 16-20 m d’altezza e con una copertura fogliare perlomeno di 5 m di spessore. In entrambe le stagioni riproduttive è stata riscontrata un’elevata sincronia tra le diverse coppie, malgrado l’assenza di vere e proprie colonie, caratteristiche nell’areale riproduttivo tipico della specie.

  10. Books reviews

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    14 48