  We investigate the eruption of a quiescent filament located close to an
active region. Large-scale activation was observed in only half of the filament
in the form of pre-eruption oscillations. Consequently only this half erupted
nearly 30 hr after the oscillations commenced. Time-slice diagrams of 171 \AA\
images from Atmospheric Imaging Assembly were used to study the oscillations.
The oscillations were observed in several thin and long features connecting the
filament spine to the chromosphere below. This study traces the origin of such
features and proposes their possible interpretation. Small-scale magnetic flux
cancellation accompanied by a brightening was observed at the footpoint of the
features shortly before their appearance, in images recorded by the
Helioseismic and Magnetic Imager. Slow rise of the filament was detected in
addition to the oscillations, indicating a gradual loss of equilibrium. Our
analysis indicates that a change in magnetic field connectivity between two
neighbouring active regions and the quiescent filament resulted in weakening of
the overlying arcade of the filament leading to its eruption. It is also
suggested that the oscillating features are filament barbs, and the
oscillations are a manifestation during the pre-eruption phase of filaments.
