Hummingbirds are some of the most beloved birds, with their tiny size, beautiful colors, and amazing flying abilities. These tiny birds play an important role in plant pollination and are indicators of environmental health. With development and climate change threatening many bird species, a common question is whether hummingbird populations are increasing or decreasing.
In the past few decades, citizen science projects like the North American Breeding Bird Survey have provided valuable data on hummingbird populations. Banding programs and bird counts by volunteers allow researchers to track migration and population changes over time. However, the data shows variable trends for different hummingbird species across North America.
Here we will examine the population trends for common North American hummingbird species over the past 50 years. Are hummingbirds increasing or decreasing in number? The data reveals complex answers, as hummingbird populations can fluctuate based on many interconnected factors.
Ruby-throated Hummingbird Trends
The ruby-throated hummingbird (Archilochus colubris) is the most widespread and common hummingbird species in eastern North America. According to the North American Breeding Bird Survey, ruby-throated hummingbirds showed a significant population increase from 1966 to 2019. The overall population trend showed a 32% increase over this time period.
Year | Population Index |
---|---|
1966 | 100 |
2019 | 132 |
What factors contributed to the increase in ruby-throated hummingbirds? One reason is the proliferation of backyard bird feeders, which provide a constant supplemental food source for hummingbirds across their breeding range. Milder winters due to climate change may also contribute to higher survival rates. Finally, planting of more exotic nectar flowers in gardens provides greater food resources.
Rufous Hummingbird Trends
The rufous hummingbird (Selasphorus rufus) migrates between the Pacific Northwest and Mexico for the winter. The population of rufous hummingbirds has declined significantly in recent years according to the Breeding Bird Survey. From 1966 to 2019, the population index declined by 53%.
Year | Population Index |
---|---|
1966 | 100 |
2019 | 47 |
What is causing rufous hummingbirds to decline so rapidly? Loss of breeding habitat due to logging and development is a major factor. Climate change also affects the availability of nectar plants and insects along their migration routes. Competition from other hummingbird species may also play a role. More research is needed to understand all the threats facing rufous hummingbirds.
Allen’s Hummingbird Trends
Allen’s hummingbirds (Selasphorus sasin) breed along the Pacific Coast and inland across the Southwestern United States. According to the Breeding Bird Survey, this species has increased significantly since 1966, with the population index rising by 308%.
Year | Population Index |
---|---|
1966 | 100 |
2019 | 408 |
The reasons for the spectacular increase in Allen’s hummingbirds are not fully clear. Urbanization and planting of ornamental flowers likely supported larger populations. Warmer temperatures allowing northward expansion of their breeding range may also play a role.
Black-chinned Hummingbird Trends
The black-chinned hummingbird (Archilochus alexandri) is a western species that migrates between the western United States and Mexico. This species has also increased significantly according to the Breeding Bird Survey data. Their population index grew by 99% between 1966 and 2019.
Year | Population Index |
---|---|
1966 | 100 |
2019 | 199 |
As with Allen’s hummingbirds, the reasons for the increase in black-chinned hummingbirds are not fully understood. Increased urbanization, backyard feeding, warmer temperatures, and more plants providing nectar all likely support larger populations across their range.
Factors Influencing Hummingbird Populations
Hummingbird population trends are clearly complex, with some species increasing and others decreasing. What are some of the key factors that influence hummingbird numbers?
Habitat Loss and Degradation
Loss of natural habitats like pine forests, scrublands, and meadows can remove important food sources for hummingbirds. If flowers and nesting sites are not available, hummingbirds cannot survive. Habitat degraded by invasive plants, pesticides, climate change, and other forces also negatively impact hummingbirds.
Pesticides and Pollution
Pesticides and other chemicals can poison hummingbirds directly when they ingest tainted nectar, pollen, or gnats. Pollution and toxins reduce the insect populations that hummingbirds rely on for food.
Climate Change
Climate change alters flowering times, nectar production, and insect hatching, disrupting the seasonal timing on which hummingbirds rely for migration and reproduction. Hotter temperatures and drought may dry up nectar sources. Severe weather events also threaten hummingbirds during migration.
Disease
Protozoan diseases spread at feeders as well as breeding ground die-offs can quickly impact hummingbird populations. Diseases may spread faster under warmer conditions enabled by climate change.
Feeders and Backyard Plantings
Backyard feeders provide a supplemental food source, which may increase survival, especially in winter. Non-native flower plantings also boost nectar availability. However, feeders must be kept clean and may enable disease transmission.
Competition and Predators
Invasive bird species, bees, and ants may compete with hummingbirds for limited nectar resources. Predators including bats, snakes, and hawks also impact hummingbird survival and nest success.
Research Methods for Studying Hummingbirds
How do scientists track hummingbird populations and study the trends over time? Some key research methods include:
Breeding Bird Surveys
Citizen scientist volunteers perform breeding bird surveys on established routes each year. Experts analyze the data to estimate population densities and trends.
Banding
Hummingbirds are captured, banded with tiny leg bands, and released. Recapturing banded birds provides data on migration routes, survival rates, and population changes.
Nest Monitoring
Researchers locate and carefully monitor hummingbird nests to determine breeding success rates and causes of nest failure. This provides insight on reproduction and survival.
Feather Sampling
Collecting and analyzing feathers determines hummingbird diet, toxin exposure, and genetic diversity. Isotope analysis can reveal migration patterns.
Feeder Surveys
Remote cameras, RFID tags, and mobile apps enable crowdsourcing of feeder usage data across the continent to supplement breeding bird survey analysis.
Radar Studies
Weather surveillance radars can detect clouds of migrating hummingbirds, allowing calculation of population sizes and migration routes.
Conclusions
– Hummingbird population trends vary significantly by species, with increases for some species like ruby-throats and declines for rufous hummingbirds.
– Habitat loss, climate change, pesticides, disease, invasive species, and other factors influence hummingbird populations.
– Citizen science data provides valuable insights but needs to be supplemented with nest studies, surveys, banding, and technology like radar tracking.
– Maintaining healthy ecosystems and mitigating climate change are key to supporting hummingbird populations into the future.
– Providing native plants, reducing pesticide use, keeping feeders clean, and participating in citizen science programs can help hummingbird conservation.
Summary
Hummingbirds face threats from many directions, but they also demonstrate resilience in the face of urbanization and habitat change. Their adaptability to floral resources and nesting locations allows them to thrive if we provide the right conditions. Continued monitoring, habitat improvements, and public engagement will give us the best chance at sustaining hummingbird populations. Though small, hummingbirds have an outsized role in ecosystem health through their extensive pollination services. Ensuring these captivating birds continue to buzz within our parks, backyards and wild areas will maintain some of the magic of the natural world.