VOLUME 26 - N. 1

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 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.