Hummingbirds are a familiar sight in gardens and backyards, easily recognizable by their tiny size, iridescent plumage, and ability to hover and fly backwards. They have an extremely high metabolism and must consume up to their entire body weight in nectar each day to maintain their energy levels. This raises an interesting ecological question – where do hummingbirds fit into food chains and food webs? More specifically, are hummingbirds tertiary consumers?
What are primary, secondary, and tertiary consumers?
Within an ecosystem, organisms can be classified by their feeding relationships known as trophic levels. Primary producers like plants and algae make their own food through photosynthesis. Primary consumers are herbivores that eat primary producers. Secondary consumers are carnivores that eat primary consumers. Tertiary consumers are carnivores that eat other carnivores.
So tertiary consumers are at the third trophic level in a food chain. They are top predators that typically feed on secondary consumers. This gives them an important ecological role in regulating prey populations. Examples of tertiary consumers include wolves, snakes, hawks, and big cats.
The diet of hummingbirds
Hummingbirds have an extremely fast metabolism – their hearts can beat up to 1,260 beats per minute and they can take up to 250 breaths per minute while resting. To support this rapid metabolism, hummingbirds need a lot of energy. Their primary food source is floral nectar from many different plant species. Hummingbirds use their specialized long bills and tongues to slurp up nectar as they hover near flowers. Some common nectar sources are from flowers of salvias, trumpet vines, and many tropical plants.
While nectar provides the main energy in a hummingbird’s diet, they also consume insects for essential proteins and nutrients. Preferred insect prey includes small spiders, aphids, fruit flies, gnats, mosquitoes, caterpillars, and insect eggs. Capturing insects provides hummingbirds with vital amino acids, vitamins, minerals, and lipids to supplement their nectivorous diet. For example, females increase insect consumption while nesting and rearing young to provide proper nutrition.
Role of hummingbirds in food chains
Based on their feeding ecology, hummingbirds can be classified primarily as secondary consumers. Nectar provides most of the energy they require, making hummingbirds nectarivores. And since the nectar is produced by plants, this means plants are the primary producers at the base of the food chain supporting hummingbirds.
The insects that hummingbirds eat are primary consumers feeding on plants. By eating these insects, hummingbirds take on a secondary consumer role. However, hummingbirds will occasionally feed on spiders and other predatory insects that are themselves secondary consumers. This technically makes hummingbirds an omnivorous secondary consumer capable of opportunistically feeding at a tertiary level.
Examples of hummingbird food chains
Here are some examples of food chains involving hummingbirds at different trophic levels:
- Trumpet vine plant → Carpenter bee (primary consumer) → Hummingbird (secondary consumer)
- Maple tree → Aphid (primary consumer) → Hummingbird (secondary consumer)
- Oak tree → Caterpillar → Jumping spider (secondary consumer) → Hummingbird (tertiary consumer)
The first two represent typical trophic dynamics where the hummingbird feeds on primary consuming insects. The third demonstrates how hummingbirds will act as tertiary consumers if given the opportunity.
Unique adaptations of hummingbirds for feeding
Hummingbirds have several unique anatomical and physiological adaptations that allow them to thrive on a nectar-based diet and engage in aerial hunting for insects:
- Needle-like bill: Perfect for sipping nectar from long, narrow flower corollas.
- Specialized tongue: Can extend past the bill tip and split into two tube-like structures ideal for lapping up nectar.
- High-speed wings: Beat up to 70 times per second, allowing superb hovering and aerial agility to snatch insects.
- Enhanced color vision: Adapted for discerning flower colors and patterns.
- Hyperactive metabolism: Requires huge amounts of energy from regular feeding on sugary nectar and protein-rich insects.
These adaptations maximize energetic returns from flowers scattered in diverse and often inaccessible locations in the hummingbird’s mountainous habitats across North and South America.
Nectar robbing by hummingbirds
In addition to legitimate nectar feeding, hummingbirds sometimes engage in “nectar robbing” where they access nectar in flowers in unintended ways. This includes piercing holes at the flower base or slitting openings in the corolla to steal nectar while avoiding pollination. Some hummingbird-pollinated flowers have even evolved protective measures against nectar robbing like toughened petals or more concealed nectar reservoirs.
While robbing nectar reduces a flower’s pollination success, this cheating behavior provides extra nourishment for hummingbirds. It allows them to efficiently exploit reliable and clumped nectar resources. One study found that up to 88% of nectar from a population of columbine flowers was robbed by broad-tailed hummingbirds rather than legitimately consumed through the flower opening.
Hummingbirds as pollinators
Although nectar robbers, hummingbirds are also extremely important pollinators for many plant species. Their ability to precisely hover in front of flowers enables hummingbirds to transfer pollen between blossoms as they feed. This gives hummingbirds a vital role in facilitating plant reproduction and gene flow between populations of certain plant species.
Plants pollinated by hummingbirds often have red tubular flowers loaded with nectar and no scent, along with curved petals that perfectly accommodate the long bills of hovering hummingbirds. Examples include lilies, fuchsias, and many tropical flowers. The coevolution between hummingbirds and specialized flowering plants dates back millions of years.
Competition for nectar resources
Given their extremely high metabolic demands, hummingbirds can be fiercely competitive over flower resources, aggressively chasing away other hummingbirds or pollinators from valuable nectar supplies. However, hummingbirds also form fascinating foraging associations with other species. For example, some tropical hummingbirds will follow spider monkeys to exploit the nectar from flowers that the monkeys expose in the forest canopy.
Other nectar feeders
Key competitors for nectar resources include:
- Bees
- Butterflies
- Moths
- Flowerpiercers (another bird)
- Orioles (certain species)
- Honeycreepers (Hawaiian birds)
The availability of flowering plants and the diversity of co-occurring nectar feeders all influence the foraging ecology of hummingbirds in a given habitat.
Do hummingbirds migrate?
Most hummingbird species that breed in North America migrate great distances to overwinter in the tropics. For example, ruby-throated hummingbirds fly nonstop across the Gulf of Mexico, an incredible 18-22 hour, 500 mile journey for such tiny birds. This allows hummingbirds to take advantage of seasonally abundant resources, feeding on flowering plants and arthropods during spring/summer breeding season in temperate zones, then shifting to tropical nectar supplies in winter.
However, some tropical and subtropical hummingbird species are year-round residents in their equatorial range and do not migrate. Rufous hummingbirds also populate summer breeding grounds along the Pacific Northwest by taking a convoluted migratory route up the edge of the Rocky Mountains rather than flying over the Gulf of Mexico.
Are hummingbird populations threatened?
Habitat loss, pesticide use, climate change, and predation pressure from invasive species have led to declines in some hummingbird populations, particularly migratory species like the ruby-throated hummingbird. However, many other hummingbird species remain widespread and relatively abundant in both tropical and temperate regions.
Providing hummingbird-friendly habitats by planting native nectar sources in gardens and minimizing pesticide usage can help support local hummingbird populations. Careful monitoring is needed to detect population trajectories in different hummingbird species.
Conclusion
To summarize, hummingbirds occupy an ecological role primarily as secondary consumers feeding on sugary nectar from flowers as well as insect prey. Their specialized adaptations allow them to thrive on this high-energy diet. While hummingbirds occasionally eat other predators and engage in nectar robbing, they more importantly serve as pollinators for numerous plant species. Their flexibility as omnivores and ability to migrate in response to resource availability has allowed hummingbirds to diversify into over 300 species across the Americas.
