Hummingbirds are some of the smallest and most fascinating birds in the world. Their ability to hover mid-air and fly backwards sets them apart from other avian species. Despite their diminutive size and delicate appearance, hummingbirds lead perilous lives in the wild. Understanding the main causes of hummingbird mortality can help us better protect these unique creatures.
Predation
Predation is one of the leading causes of death for wild hummingbirds. Their small size makes them vulnerable to a wide range of predators. Birds of prey such as falcons, hawks and shrikes frequently prey on hummingbirds. Snakes, lizards, frogs, spiders and praying mantises will also eat hummingbirds when given the opportunity.
Nestlings and fledglings are especially susceptible to predation since they cannot fly away from danger. Common nest predators include snakes, squirrels, chipmunks, rats, cats, and birds like jays, crows and grackles. Parent hummingbirds fiercely defend their nests from intruders, but they are not always successful in fending off predators.
Adult hummingbirds may be taken unaware by stealthy predators like praying mantises that camouflage themselves as flowers or leaves. Larger birds of prey surprise hummingbirds in midair or ambush them from perches. The bold colors and iridescent plumage that make hummingbirds so breathtaking to humans also unfortunately make them more visible to predators.
Starvation
Starvation is another major cause of mortality in hummingbirds. Because of their hyperactive metabolism, hummingbirds need to consume more than their weight in nectar each day to fuel their energy needs. Hummingbirds starve when they cannot find enough flowers and feeders with adequate nectar to meet their high energy requirements.
Migration puts hummingbirds at greater risk of starvation. Making long seasonal journeys leaves less time and energy for foraging. Adverse weather conditions like storms, winds and rain can prevent hummingbirds from feeding properly during migration. Lack of flowering plants or feeders along migration pathways also leads to starvation.
In residential and urban areas, disappearance of feeders or ornamental flowers when homeowners go on vacation results in starvation. Similarly, droughts in the wild reduce natural nectar supplies. Due to their specialized nectar diet, hummingbirds have no other food alternatives when normal nectar sources are unavailable.
Collisions
Collisions are a frequent cause of injury and mortality in hummingbirds. Windows claim many hummingbird lives as the birds smash into invisible panes. Vehicle strikes also kill countless hummingbirds every year.
Younger hummingbirds just learning to fly are especially prone to collisions. Their lack of flying experience leads them to blunder into windows and vehicles. During courtship and territorial displays, adult male hummingbirds focus intently on chasing rivals and impressing females. This diverts their attention from potential hazards in their path.
Migrating hummingbirds traveling through unfamiliar terrain are at higher risk of collisions. Exhaustion diminishes their reflexes and reaction time. Hummingbirds migrating at night or in foggy conditions are more likely to collide with towers, buildings, wind turbines, power lines and other structures.
Diseases
Hummingbirds are susceptible to a number of infectious diseases that can be fatal including:
- Aspergillosis – Fungal respiratory infection
- Avian malaria – Parasitic disease transmitted by mosquitoes
- Candidiasis – Fungal infection
- Chlamydiosis – Bacterial disease
- Pox – Viral skin infection
- Salmonellosis – Bacterial food poisoning
- Trichomoniasis – Parasitic infection
- West Nile virus – Mosquito-borne virus
The viruses, bacteria, parasites and fungi that cause these diseases thrive in unsanitary living conditions. Contaminated feeders, bird baths and nesting areas promote transmission. Stressed, starved, injured and fledgling birds have weakened immunity and are most prone to succumbing to these diseases.
Pesticides
Pesticide poisoning poses a substantial threat to hummingbirds. Since hummingbirds feed on flower nectar, they ingest any pesticides or herbicides applied on plants. The synthetic chemicals interfere with hummingbirds’ metabolism, reproduction, endocrine system and immune function. Pesticides can kill hummingbirds outright or have chronic effects that gradually degrade their health.
Common pesticides implicated in hummingbird deaths include organophosphates, neonicotinoids and glyphosate. Using pesticides and herbicides sparingly, or avoiding them altogether, greatly reduces the pesticide exposure and risk for hummingbirds and other pollinators.
Extreme Weather
Extreme weather events like storms, floods, heatwaves and cold snaps kill hummingbirds directly or indirectly by degrading their habitat and limiting their food supply. Intense storms may blow fledglings out of nests before they can fly or drown hummingbirds in floodwaters.
Prolonged extreme heat causes heat stress, dehydration and hyperthermia in hummingbirds. Frigid temperatures during unusual cold spells can freeze hummingbirds to death. Both hot and cold extremes impact flowering schedules and nectar availability.
Hummingbirds evolved to thrive in specific microclimates and are highly sensitive to weather changes. Global warming increases the frequency and severity of extreme weather, heightening threats to hummingbirds from storms, floods, heatwaves and unseasonal frosts.
Habitat Loss
Widespread habitat destruction also contributes to hummingbird mortality. Urbanization, agriculture, ranching, logging and mining destroy natural meadows and forests hummingbirds depend on for food and shelter. Deforestation in tropical wintering grounds threatens species like the Ruby-throated Hummingbird.
Development near water depletes riparian areas that provide essential oases for migrating hummingbirds. Natural habitat loss is a key factor in the endangerment of specialized species like the Rufous Hummingbird that rely on certain ecosystems.
Providing backyard habitats with native plants, trees, flowers and feeders can offset habitat impacts near homes. Preserving wild spaces through conservation helps protect essential hummingbird habitat.
Conclusion
Hummingbirds captivate us with their beauty, but they lead surprisingly perilous lives in nature. Predators, starvation, collisions, diseases, pesticides, weather extremes and habitat loss all contribute to high mortality rates. While individual survival is precarious, most hummingbird species continue to thrive overall through prolific reproduction.
Supporting hummingbird conservation helps protect these special birds. Providing clean feeders, limiting pesticide use, preserving habitat, reducing collisions through awareness and contributing to research all make a difference. With diligent stewardship, we can continue enjoying hummingbirds for generations to come.
