Ten years tracking the migrations of small landbirds: Lessons learned in the golden age of bio-logging
The Auk Ornithological Advances
By Emily McKinnon and Oliver Love
Since miniature light-level geolocators were first deployed on small songbirds (2007), our understanding of migration for this group has grown exponentially. In this paper, 127 studies were reviewed that used geolocators to track small landbirds.
The majority of research (54%) resulted in natural history descriptions of a critical life history phase (e.g non-breeding location, migration route). Studies also tested behavioural (20.5%) and evolutionary hypotheses (9%), constructed range-wide migratory connectivity maps (11%) and tested for seasonal interactions (5.5%). New tracking options, such as archival GPS tags and automated telemetry systems, can be used to build on the information obtained from light-level geolocators. Archival GPS tags are accurate to within metres. New models can record >100 fixes, and will provide much-needed detail on year-round habitat use. Automated telemetry has provided insights into stopover biology and is well-suited for studying carry-over effects of breeding on migration departure decisions. Most recently, the landscape-scale deployment of receiving towers is allowing automated telemetry systems to be used for studying long-distance movements.
Gaps remain in our understanding of flexibility of migration, especially in irruptive or ‘nomadic’ species. The genetic basis of migration is still largely unknown. Carry-over effects of breeding/non-breeding events on start-to-finish migration are still poorly understood in most cases. Migratory connectivity can now be quantified with more sophisticated spatial statistics. Tracking of proportionally more females, repeat-tracking of the same individuals, and targeting species from under-represented flyways (i.e. within continental Africa, Central Asia) would also lead to further insight into migration behaviour.
Migratory birds around the world are declining, and the information gathered by researchers deploying tracking tags often has a critical role to play in identifying conservation targets. The ‘golden-age of bio-logging’ will continue with ICARUS (space-station-based tracking system), set to come online in 2019.
(c) The Auk Ornithological Advances