| Titre : | The daily activity of wintering Common Cranes Grus Grus in Portugal: The effect of scarce food resources |
| Auteurs : | Martim P. Melo, Auteur ; Julia Almeida, Auteur ; Alexandre Vaz, Auteur ; Rita Covas, Auteur |
| Type de document : | Article |
| Dans : | Vogelwelt (Die) (120(5-6) 1999) |
| Article en page(s) : | 353-356 |
| Résumé : | Daily activity studies are an important complement to habitat utilisation studies in order to fully understand the needs of a species in the area where it occurs. In Portugal's main wintering site, time budget and flock dynamics of the Common Crane were studied in the winter periods 1994-1995 and 1995-1996, the last two years of a long drought period. Visits were made every two weeks from November to March. The behaviour of Cranes was recorded by 3 min focal animal sampling in every daylight hour. Flock size, % of juveniles and distance to nearest roost were recorded. Time budget was determined by energetic requirements. Daily activity was characterised by a constant high feeding effort during most of the day with only a small decrease from 2.00 to 4.00 p.m.: this difference to the "classical" double-peak pattern of feeding effort could be a result of the low food availability. Preening occupied discrete periods where no feeding occurred. Vigilance effort was constant during the day. In the morning, when feeding activity was maximal, a peak in preening bouts suggested interindividual differences in time budgets. This difference could be a result of competition and reflect the existence of dominance-subordinate relations in wintering cranes. Cranes dispersed more during the morning, aggregating in larger flocks closer to the roost during the afternoon. In general, flock dynamics seemed related to distribution of food resources, with a weak tendency for segregation of the families from the non-reproductive individuals. |
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