Experimental manipulation of photoperiod influences migration timing in a wild, long-distance migratory songbird

Previous laboratory studies have demonstrated the role of photoperiod in
cueing the migration timing of small land birds; however, how migration
timing of young birds in wild environments develops in relation to these
cues have rarely been investigated. Such investigations can make important
contributions to our developing understanding of the phenotypic plasticity
of migration timing to new conditions with climate change, where changes
in the timing of nesting may expose juvenile birds to different
photoperiods. We investigated the impact of manipulating photoperiod
during nestling development in a long-distance migratory songbird on the
timing of post-breeding movements in the wild. Using programmable lighting
installed in the nest-boxes of purple martins (Progne subis), we exposed
developing nestlings, from hatch to fledge date, to an extended
photoperiod that matched the day length of the summer solstice in
Manitoba, Canada. We found that birds with a simulated, earlier
photoperiod had a longer nesting period and later fledge and autumn
departure dates than control group birds. This study demonstrates the
phenotypic plasticity of first-year birds to the ontogenetic effect of
their hatch date in the formation of the timing of their first
post-breeding movements. Further, we discuss how these results have
implications for the potential use of assisted evolution approaches to
alter migration timing to match new conditions with climate change.