Hummingbirds are one of the most beloved backyard birds, prized for their jewel-like colors and incredible flying skills. Their ability to hover in midair as they sip nectar from flowers is a sight that captivates bird enthusiasts and casual nature lovers alike. However, there are concerns that hummingbird populations may be declining in recent years. In this article, we’ll explore the evidence for and against a decline in hummingbird numbers.
What is a hummingbird?
Hummingbirds are small birds that comprise the family Trochilidae. There are over 300 different species, found only in the Americas from Alaska to Chile. They are known for their rapid wing beats, which allow them to hover and fly backwards and upside down. Their heart rates can reach over 1,200 beats per minute during flight.
Hummingbirds have long slender bills adapted for accessing nectar from flowers. They prefer tubular blooms with high energy nectar. Their diet is supplemented by small insects which provide key proteins.
These tiny birds perform a vital role as pollinators. As they access nectar, pollen sticks to their heads and bills and is transferred to the next flower they visit. Plants rely on hummingbirds, bees, butterflies and other pollinators to reproduce and create seeds, fruits, and nuts.
Where do hummingbirds live?
Hummingbirds are found only in the Americas. Roughly half of all species live in South America, while North America is home to around 12 species. The habitats they occupy include tropical rainforests, mountain meadows, deserts, and both coastal and inland scrublands.
In North America, some of the most widespread hummingbird species include:
- Ruby-throated Hummingbird: Eastern states
- Anna’s Hummingbird: Western states
- Rufous Hummingbird: Northwest to Alaska
- Allen’s Hummingbird: California coast
- Calliope Hummingbird: Western mountains
Evidence of declining populations
There are several sources of information that point to potential declines in hummingbird numbers in recent decades:
Breeding Bird Survey data
The Breeding Bird Survey is a long-running program by the U.S. Geological Survey that tracks bird population trends. Volunteers conduct surveys on roadside routes across the continent during the breeding season. The data is used to estimate population sizes and changes over time.
Analysis of BBS data from 1966-2013 suggests declines in the majority of regularly occurring hummingbird species in the U.S. and Canada:
- Rufous Hummingbird declined by 3.7% per year
- Black-chinned Hummingbird declined by 1.7% per year
- Ruby-throated Hummingbird declined by 0.9% per year
- Only the Anna’s Hummingbird showed a population increase, at 1.3% annually.
However, BBS data has limitations when applied to hummingbirds. The surveys are conducted along roadsides and may not be representative of hummingbird populations across landscapes as a whole. The surveys are also done in early morning when hummingbirds are less active.
Feeder surveys
Another source of information on hummingbird numbers comes from backyard feeder surveys. For example, the Hummer/Bird Study Group runs a spring and fall survey where volunteers report the hummingbirds seen at their feeders during a two-week period.
Analysis of these reports suggests a decline in sightings for some species. Comparing the average number of birds reported per survey site in 1987-1991 versus 2012-2016 showed:
- Rufous Hummingbird declined by 45%
- Black-chinned declined by 22%
- Broad-tailed declined by 17%
However, as with the Breeding Bird Survey, feeder surveys may not represent overall population trends. Participation varies between years and regions. The numbers of birds using feeders can be influenced by many factors such as flowering plant availability.
Habitat loss
Hummingbirds are threatened by habitat loss in many regions from development, logging, fires and climate change. For example, the extinct Blue-bearded Helmetcrest hummingbird of Colombia was restricted to a few mountaintop cloud forests that were heavily logged and cleared.
As hummingbirds have specialized habitat preferences and migration routes, they may be unable to adapt when human activity alters their environment. Ongoing habitat degradation and destruction is an underlying driver of risk for many hummingbird species.
Evidence against declining populations
While some data sources indicate hummingbird declines, other information suggests populations may be stable or increasing:
Stable Partners in Flight estimates
Partners in Flight is a cooperative bird conservation group that develops status assessments for bird species’ populations. Their estimates for 26 species of North American hummingbirds suggest most have breeding populations in the millions or tens of millions.
Just four hummingbird species were given a status of High Concern:
- Allen’s Hummingbird
- Rufous Hummingbird
- Calliope Hummingbird
- Buff-bellied Hummingbird
The remaining species were ranked as moderate concern or low concern, indicating their populations are likely stable.
Increasing sightings
There are many anecdotal reports of hummingbirds expanding their ranges northward and to higher elevations. This may indicate populations adapting to climate change as warmer temperatures allow the birds to breed in new areas.
For example, Ruby-throated Hummingbirds were traditionally an eastern species. But sightings have increased dramatically in western states, suggesting the species is expanding its territory.
Citizen science databases like eBird show increasing observational records for hummingbirds in many areas, particularly for species like Anna’s and Rufous Hummingbirds. These suggest range expansions likely linked to global warming.
Backyard habitat programs
One of the main threats to hummingbirds is loss of feeding and breeding habitat. But programs encouraging homeowners to landscape for wildlife may offset those impacts. For example:
- Audubon’s Plants for Birds program guides people to add native flowering plants to yards.
- The National Wildlife Federation has certified over 150,000 backyard habitats across the U.S.
As more people provide habitat, localized conditions and resources for hummingbirds may improve, supporting stable or increasing numbers.
Research needs
The uncertainty around hummingbird population trends highlights the need for more research. Some approaches that could provide clarity include:
Expanded monitoring programs
Surveys specifically targeting hummingbirds are needed, as Breeding Bird Surveys have significant limitations. More geographic coverage and year-round monitoring would provide better trend data.
Banding studies, where birds are captured and marked to track migrations and survival, provide important life history data. Expanding hummingbird banding programs would augment survey results.
Tracking populations genetically
Analyzing genetic markers from feathers and blood samples helps estimate population sizes. Comparing genetic diversity over time can reveal if populations are declining.
Targeted studies of at-risk species like the Rufous Hummingbird or Buff-bellied Hummingbird may clarify their conservation status.
Understanding migration routes
Many hummingbird species make incredible multi-stage migrations. Documenting their migratory connectivity and stopover locations is critical.
Technologies like tiny geolocator tags can map migration pathways and identify key sites. With this data, efforts to protect habitat can be targeted along entire flyways.
Filling in life history knowledge gaps
For many hummingbird species, basics on lifespan, breeding biology and habitat needs are still poorly known. Filling these information gaps would allow modeling of extinction risk and population viability.
Causes of hummingbird declines
If some hummingbird species are indeed declining, what factors may be contributing? Potential causes include:
Habitat loss and degradation
Hummingbirds are highly adapted to specific habitat niches like subalpine meadows and tropical forests. Logging, development, agriculture and other human land uses reduce available habitat and floral resources. For migratory species, habitat loss on the breeding grounds, wintering grounds and along migration routes may all impact populations.
Pesticides and insect declines
Insects make up an important part of hummingbird diets. However pesticide use, introduced species and broader insect declines may limit this food source. Neonicotinoids and other common pesticides are implicated in reducing insect populations, and may indirectly affect the birds relying on them.
Climate change
Climate warming could disrupt hummingbird populations in complex ways. Ranges may shift out of sync with flower timing. Extreme heat, droughts or wildfires may affect breeding areas and food supplies. Migratory species rely on environmental cues to move between areas, which global warming may disrupt.
Disease
Hummingbirds may suffer from avian malaria and other diseases spread by mosquitoes. West Nile Virus has killed Blue-throated Mountain-gem hummingbirds and other species. As climate change alters insect ranges, new disease risks for hummingbirds may emerge.
| Cause | Effects on Hummingbirds |
|---|---|
| Habitat loss and degradation | Loss of feeding, breeding and migratory sites |
| Pesticides and insect declines | Reduced insect food sources |
| Climate change | Shifting migration patterns and mistimed breeding |
| Disease | Higher mortality from West Nile Virus, malaria, etc. |
Backyard bird feeding
Ironically, one factor that may reduce wild hummingbird populations is backyard bird feeding. Hummingbirds may grow dependent on sugar water solutions from unmaintained feeders. This may reduce their natural foraging behaviors and nutritional health.
Feeders may also concentrate birds unnaturally and increase disease transmission of parasites like trichomonosis. Experts encourage cleaning feeders regularly and using feeders more as a supplement than sole food source for hummingbirds visiting backyards.
Conclusion
The evidence for hummingbird declines is still inconclusive and mixed. While some species like the Rufous Hummingbird show concerning trends in long-term surveys, other data suggests stabilization or adaptations to a changing world.
Ongoing habitat loss coupled with new stressors from climate change and pesticide impacts present risks. However, conservation initiatives focused on hummingbirds help counteract these threats. Continued monitoring along with targeted research on at-risk species will shed more light on their status.
The allure of these smallest of birds remains strong. With their glittering colors, entertaining antics, and almost magical flight, they hold a special place in the wildlife communities they inhabit. Time and care is needed to ensure hummingbird populations persist into the future.
