Breeding phenology and productivity of ducks in rivers of the Tajo Valley.

Full article

Published:

Volume 43(1), June 1996. Pages 31-39.

Language:

Spanish

Original title:

Fenología de la reproducción y productividad de anátidas en ríos del valle medio del Tajo

Keywords:

abundance, breeding phenology, brood size, ducks, rivers, Tajo Valley.

Abstract:

Ducks breeding in the Henares, Manzanares, Jarama and Tajo rivers at Madrid and Toledo provinces were censused. Breeding species were Mallard Anas platyrhynchos, Gadwall Anas strepera, Shoveler Anas clypeata, Red-crested Pochard Netta rufina and Pochard Aythya ferina. Mallards were the most abundant ducks, especially at the Tajo river. All the other species showed lesser abundances, always being more numerous at the Tajo river except for the breeding abundance of Pochards in the Jarama river (1.6 pairs/km). The earliest Mallard broods were observed on April (first and last hatchings occurred in March and July). Pochards showed a late breeding phenology, with most hatchings in July. Mallard brood size decreased 1.8 ducklings in average across the growing period. The same trend was observed in Gadwalls but not in Pochards. The average number of young produced per successful female was 4.9 in Mallard and 5.5 in Pochard.