Rufous hummingbirds undertake one of the longest migrations relative to body size of any bird, dependent on precisely timed nectar availability along their route.
Rufous hummingbirds face welfare challenges from climate-driven phenological mismatches: if flowers peak before birds arrive on northward migration, early season food sources are depleted during the critical period of territorial establishment and breeding. Hummingbirds have extremely high metabolic rates and can enter torpor overnight to conserve energy but cannot survive multi-day food shortages. Habitat loss reducing floral diversity along migration routes creates energy bottlenecks causing welfare impacts and mortality.