Data from: Immature gannets follow adults in commuting flocks providing a potential mechanism for social learning

Group travel is a familiar phenomenon among birds but the causes of this
mode of movement are often unclear. For example, flocking flight may
reduce flight costs, enhance predator avoidance or increase foraging
efficiency. In addition, naive individuals may also follow older, more
experienced conspecifics as a learning strategy. However, younger birds
may be slower than adults so biomechanical and social effects on flock
structure may be difficult to separate. Gannets are wide-ranging
(100s-1000s km) colonial seabirds that often travel in V or echelon-shaped
flocks. Tracking suggests that breeding gannets use memory to return
repeatedly to prey patches 10s–100s km wide but it is unclear how these
are initially discovered. Public information gained at the colony or by
following conspecifics has been hypothesised to play a role, especially
during early life. Here, we address two hypotheses: (1) Flocking reduces
flight costs and (2) young gannets follow older ones in order to locate
prey. To do so, we recorded flocks of northern gannets commuting to and
from a large colony and passing locations offshore and used a
biomechanical model to test for age differences in flight speeds.
Consistent with the aerodynamic hypothesis, returning flocks were
significantly larger than departing flocks, while, consistent with the
information gathering hypothesis, immatures travelled in flocks more
frequently than adults and these flocks were more likely to be led by
adults than expected by chance. Immatures did not systematically occupy
the last position in flocks and had similar theoretical airspeeds to
adults, making it unlikely that they follow, rather than lead, for
biomechanical reasons. We therefore conclude that while gannets are likely
to travel in flocks in part to reduce flight costs, the positions of
immatures in those flocks may result in a flow of information from adults
to immatures, potentially resulting in social learning.