Mitochondrial remodeling supports migration in White-crowned Sparrows (Zonotrichia leucophrys)

The migratory movements undertaken by birds are among the most
energetically demanding behaviors observed in nature. Mitochondria are the
source of aerobic energy production on which migration depends, but a key
component of mitochondrial function, mitochondrial remodeling, has not
been investigated in the context of bird migration. We measured markers of
mitochondrial remodeling in the skeletal muscles of the Gambel’s
(migratory) and Nuttall’s (non-migratory) White-crowned Sparrows within
and outside migratory periods. Gambel’s were collected in 1) a
non-migration period (baseline), 2) preparation to depart for spring
migration (pre-migration), and 3) active autumn migration (mid-migration).
Nuttall’s were collected at time points corresponding to baseline and
mid-migration in Gambel’s. Across all sampling periods, we found that
migratory birds had greater mitochondrial remodeling compared to
non-migratory birds. Furthermore, birds from the migratory population also
displayed flexibility, increasing several markers of mitochondrial
remodeling (e.g., NRF1, OPA1, Drp1) pre- and during migration. Further,
the greater levels of mitochondrial remodeling and its upregulation during
migration were specific to the pectoralis muscle used in flapping flight.
Our study is the first to show that mitochondrial remodeling supports
migration in Gambel’s White-crowned Sparrows, indicating a highly specific
and efficient phenotype supporting the increased energetic demands of
migration.