[OANNES Foro] Immature gannets follow adults in commuting flocks

[Fiorella Sala]

Journal of Avian Biology

First published: 18 September 2019

 <https://doi.org/10.1111/jav.02164> https://doi.org/10.1111/jav.02164





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



<https://onlinelibrary.wiley.com/action/doSearch?ContribAuthorStored=Wakefie
ld%2C+Ewan+D> Ewan D. Wakefield
<https://onlinelibrary.wiley.com/action/doSearch?ContribAuthorStored=Furness
%2C+Robert+W> Robert W. Furness
<https://onlinelibrary.wiley.com/action/doSearch?ContribAuthorStored=Lane%2C
+Jude+V> Jude V. Lane
<https://onlinelibrary.wiley.com/action/doSearch?ContribAuthorStored=Jeglins
ki%2C+Jana+W+E> Jana W. E. Jeglinski
<https://onlinelibrary.wiley.com/action/doSearch?ContribAuthorStored=Pinder%
2C+Simon+J> Simon J. Pinder





Abstract


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.





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