It is known that birds inhabiting temperate regions accumulate fat in order to survive a night of extreme conditions. Levels of fat depots arise as the day goes by, reaching its pick at dusk and decreasing along the night hours when no feeding is possible. Allied to this fact, there is a seasonal increase of the lipid stores as the winter gets closer, which enable the bird to survive through this season. Data on tropical birds are however rare. This study concerns the knowledge of the fat dynamics of the Rufous-fronted Thornbird Phacellodomus rufifrons (Wied, 1821), an ovenbird (Passeriformes, Furnariidae) endemic of the Neotropical region, on a seasonal tropical environment, the Southeastern Brazilian Cerrado, a savannah-like ecosystem. The fieldwork was carried out between August 2001 and July 2002 at Serra do Cipó National Park, municipality of Jaboticatubas in the state of Minas Gerais. The data on subcutaneous fat was visually scored on the captured individuals. As the furcular subcutaneous amount of lipid varied, it was established four categories for this parameter. We found out that there was a significant increase of the fat levels along the day, as in the temperate region species, but there was not a significant seasonal variation. Also the mean body weight did not change throughout the year or throughout the day. Our results show that the daily variation in the Cerrado region can act as a stressing situation that could lead to overnight physiological adaptation. On the other hand, seasonal variation could be balanced by the habit of sleeping all year long inside the nest, a behavior relatively rare for passerine birds.
Body weight; Cerrado; Serra do Cipó; winter fattening
