According to Kiran Dhanjal-Adams at the University of Queensland, a lifestyle on the move is not without risk. Migration is physically demanding, and migratory species are highly reliant on places to stop, rest and feed along the way. Unfortunately, human activities are making it riskier for animals to travel, while also reducing the number of places they can travel to. Fishing, culling, fence-building, deforestation, land-reclamation and plastic pollution are all making it increasingly difficult for many species to migrate. So much so, that migratory species populations are declining at much greater rates than non-migratory species.
This suggests that current conservation strategies are not working as well as we would like them to. We are still at the early stages of understanding migration, and data detailing where, when and how far many species migrate is still sparse. Though a few individuals of some species have been tracked, it remains unclear how these few tracked individuals reflect the migration patterns of an entire species.
Because of this poor understanding of where animals migrate, conservation strategies are currently set using the data we have – animal counts. Indeed, it is not unreasonable to assume that sites with lots of migrants are probably more useful to the population than sites with fewer migrants. However, research is increasingly showing that where these sites are relative to each other is equally important. This is because the distance between two sites is likely to impact the number of animals able to travel between the two. Connected sites are therefore more useful to the population than unconnected sites.
Pic: Catching and tagging birds is a large part of understanding where they migrate. However, if we tag a few birds in multiple locations, we can learn more about how the population behaves as a whole, than if we tag many birds in the same location. (Photo by Kiran Dhanjal-Adams)