Is climate change putting migratory birds at risk?

The survival of these migratory species is threatened not by one catastrophic event, but rather by an accumulation of pressures. Throughout the year, migratory birds travel between distant habitats that span countries and continents. Hans Linssen, a movement ecologist at the University of Amsterdam, said that “migratory birds are especially vulnerable precisely because they migrate”. Human-led factors such as climate change, hunting, and agricultural expansion all impact the decline of migrating species, and they don’t face threats in one location; rather, threats are faced across the globe.

 Climate change is one stressor that has vast consequences on many of the species flyways. Warming temperatures alter the ecosystems of the planet, rendering habitats once ideal no longer suitable for stop-off or breeding. Equally, warming and consequent droughts have effects on food availability throughout their journey. Whilst climate change is a pressure during migration, Thomas Lameris, migration ecologist at Groningen University, noted that “climate change alone is rarely the main major factor impacting population decline in these birds”.

Despite increasing stressors, the birds’ ability to adapt to alternative migratory patterns is proving possible. Thomas said that there are “more and more indications that birds are tremendously flexible to adjust their own timing”, meaning birds are arriving earlier, travelling faster, or making fewer stops. Despite this, timing changes during one migration don’t necessarily correlate to indefinite adaptation. A key factor in their ability to adjust depends upon food availability at staging and wintering sites. Staging sites are locations where birds stop during migration to rest and feed before continuing their journey. Unsuitable habitats have less food, meaning the birds cannot adequately refuel. Hans says that the birds may struggle to find enough food at certain staging sites, arriving at the next place in weaker condition, potentially affecting their breeding success.

 For Arctic breeding birds, Hans says, the rising temperatures in the Arctic regions are shifting suitable habitats further north. This is particularly disruptive, as there is only so far that these birds can go. Furthermore, species moving up from the south will increase competition for habitats and food sources.

The conservation efforts for these birds must protect the chain of migration, not individual links. BirdLife International emphasised the need for international cooperation and conservation across entire flyways. If a stopover disappears, a protected breeding ground isn’t sufficient for the survival of the birds; if the birds are being hunted in one location, a restored wetland will not protect them outside of it. “In order to help birds adapt, we need to conserve the vital staging sites of migratory birds”, says Thomas.

“Protecting them in one place will not save a population if it’s suffering threats in a different place”, says Hans. For migratory birds, survival does not depend on one safe location but on a chain of places remaining habitable throughout their international journey.