Hummingbirds are a beloved backyard visitor for many people. Their rapid wing beats, audible hum, and bright iridescent colors make them a joy to watch. However, over the past several decades, hummingbird populations have been declining across North America. Understanding the causes and extent of these declines is an important step in developing conservation strategies to protect these unique birds.
Why are hummingbird populations declining?
There are several key factors that have led to decreasing hummingbird numbers:
- Habitat loss – Development, logging, and agriculture have destroyed and fragmented hummingbird habitat across North America. Hummingbirds rely on native flowering plants and trees for food and nesting sites.
- Pesticides – The widespread use of insecticides and herbicides has reduced insect populations that hummingbirds rely on for food. Pesticides can also poison hummingbirds directly.
- Climate change – Changing weather patterns, increased storms, droughts, and wildfires have impacted flowering cycles and food availability. Range shifts in response to climate change may also put stress on some hummingbird populations.
- Disease – Avian diseases have become more prevalent and may be contributing to hummingbird mortality.
- Predators – Growing populations of hummingbird predators, like house cats, may be increasing mortality rates, especially where habitat is already degraded.
The synergistic effects of all these factors are likely driving the observed declines in hummingbird abundance across their ranges.
How severe are the population declines?
Research shows that hummingbird populations have declined significantly since the 1960s and 1970s when surveys first began tracking their numbers systematically. Some examples:
- Rufous hummingbird populations in California declined by over 60% between 1970 and the late 2000s.
- In the eastern US, ruby-throated hummingbird numbers declined by an estimated 35% between 1966 and 2014, based on Breeding Bird Survey data.
- Once common in central California, Allen’s hummingbirds have disappeared from much of their range since the 1970s.
- Broad-tailed hummingbird populations at migration hotspots declined by up to 75% in some areas between 1998 to 2013.
Both short-distance and long-distance migratory hummingbird species have exhibited significant population reductions. This suggests the declines are being driven by broad-scale environmental factors occurring across their breeding and migratory ranges.
Which species are most threatened?
While all North American hummingbirds have shown concerning population trends, these species are particularly vulnerable:
- Rufous hummingbird – This abundant western species has declined more dramatically than any other hummingbird. Habitat loss in its Pacific Northwest breeding range and climate threats to food supplies are major factors.
- Allen’s hummingbird – This coastal California hummingbird has suffered severe declines likely due to urbanization, loss of flowering plants, and expanding ranges of competitor Anna’s hummingbirds.
- Violet-crowned hummingbird – Restricted to Mexico’s dwindling pine-oak forests, it is threatened by deforestation and could lose more than half its range by 2080 due to climate change.
- Blue-throated mountain-gem – Only a few hundred individuals remain of this endangered Central American highland hummingbird, threatened by habitat loss and climate change.
Other threatened species include the berylline hummingbird, Bahama woodstar, Esmeraldas woodstar, and the mangrove hummingbird. Many Neotropical hummingbirds restricted to mountaintop cloud forests also face extinction risk from warming climates.
How does climate change threaten hummingbirds?
Climate change poses various threats to hummingbirds:
- Flower/food mismatch – Hummingbirds’ migrations and breeding are timed with spring flowering. Climate change can cause mismatches between peak food needs and food availability.
- Extreme weather – Droughts, heat waves, and storms can kill hummingbirds or reduce nesting success. More wildfires also destroy habitat.
- Shifting ranges – Climate shifts may force hummingbirds to new areas, increasing competition for resources in those regions.
- Altitudinal migration – Warming temperatures are pushing some high elevation tropical species up mountainsides with little room left to move.
Climate change models predict declines of current hummingbird habitat ranges by over 50% in some cases. Their specialized adaptations make hummingbirds particularly vulnerable to these rapidly changing conditions.
What can be done to help hummingbird populations?
While the threats are complex, there are actions that can aid hummingbird conservation:
- Plant native flowers, trees, and shrubs to restore habitat, especially along migration routes and protected areas.
- Avoid or limit pesticide use which reduces prey insects that hummingbirds depend on.
- Keep domestic cats indoors to reduce hummingbird predation.
- Install nectar feeders, pollinator gardens, and birdbaths in backyards to supplement natural food and water sources.
- Support policies to expand protected areas, improve climate resilience, and reduce carbon emissions.
- Participate in citizen science programs to track hummingbird populations and inform conservation strategies.
Protecting hummingbird habitat and mitigating climate change impacts are key to stabilizing populations. Given their ecological importance as pollinators and their cultural legacy, reversing hummingbird declines is an urgent priority.
Conclusion
Hummingbirds face a concerning array of threats driving substantial population reductions across North America. Habitat destruction, pesticides, disease, predators, and climate change impacts are all contributing factors to declines observed in long-term surveys. Species like the rufous hummingbird and Allen’s hummingbird are particularly imperiled and require targeted conservation efforts. Climate change may be the most challenging threat going forward as it disrupts migration and breeding cycles. Protecting and restoring habitat, reducing carbon emissions, and citizen engagement in conservation programs will be critical to the future of these unique pollinators. With committed action, it may be possible to reverse hummingbird population declines before it is too late.
