Hummingbirds are attracted to the sweet nectar inside flowers as their main food source. They have specialized beaks and tongues that allow them to reach deep inside flowers to access the nectar. However, ants are also attracted to nectar and will often crawl onto flowers to drink the sugary liquid. This raises an interesting question – if ants have already been on a flower and tasted or contaminated the nectar, will hummingbirds still feed from that flower? In this article, we will explore the evidence around hummingbird feeding preferences when ants are present.
Do Hummingbirds Avoid Flowers with Ants?
Several studies have investigated the interactions between hummingbirds and ants on flowers. The results show that hummingbirds do tend to avoid flowers that have ants present. In one study in Arizona, researchers found that broad-billed hummingbirds were much less likely to feed from artificial flowers if harvester ants were already on them. The hummingbirds would avoid those flowers and instead feed from different clean flowers without ants.
Another study in California looked at Anna’s hummingbirds feeding from real flowers. They found the hummingbirds spent significantly less time feeding at flowers that had ants present. On average, the hummingbirds only made one-fifth as many visits to flowers with ants compared to flowers without ants.
The research indicates that hummingbirds can detect the presence of ants visually and will preferentially avoid feeding from those flowers. This avoidance behavior suggests hummingbirds are sensitive to the risk of interference or contamination from ants while feeding.
Do Ants Contaminate or Deplete Nectar?
There are a couple reasons why hummingbirds may avoid flowers with ants:
Nectar Depletion
Ants will consume nectar from flowers, which depletes the amount of food available for hummingbirds. In some cases, ants can drain flowers of up to 90% of their nectar. This can make the flower less energetically rewarding for the hummingbird. They likely avoid heavily ant-attended flowers to avoid expending energy for minimal nectar intake.
Nectar Contamination
Ants can also contaminate nectar by spreading microbes and other small particles when they feed. Their legs and mouthparts frequently touch pollen and debris that can then get deposited into the nectar. Some microbes transmitted by ants are pathogenic and potentially dangerous to hummingbirds. The nectar in ant-visited flowers has been found to have higher microbial loads. Hummingbirds seem to be able to detect this contamination and prefer to avoid it.
Some experts speculate the ant-derived microbes may also negatively alter the taste of nectar, making the hummingbirds less likely to feed from contaminated flowers. However, more research is needed on how microbial loads actually impact nectar palatability.
Exceptions – When Do Hummingbirds Feed from Ant-Visited Flowers?
While hummingbirds generally avoid flowers with ants, there are some circumstances when they will still feed from ant-visited flowers:
When Nectar is Limited
During times of drought or scarcity when nectar is limited, hummingbirds may be less choosy. If few flowers are available, they cannot afford to skip ant-visited ones and will risk feeding from them.
When Ants are Present in Very Low Numbers
Hummingbirds seem to make calculated decisions based on the density of ants on a flower. If only one or two ants are present, the nectar depletion and contamination risk is lower. Some studies have found hummingbirds will feed from flowers with up to five ants present.
When the Benefit Outweighs the Risk
Flowers that are especially rich in nectar, or flower species that a hummingbird particularly prefers, may still be visited by the birds even with some ants present. If the payoff is high enough, hummingbirds will take the gamble.
Young, Inexperienced Hummingbirds
Juvenile hummingbirds with less exposure may be more likely to try feeding from ant-occupied flowers. As they gain experience, they learn to identify and avoid flowers with contamination risks.
How do Ants Impact the Feeding Behavior of Hummingbirds?
The presence of ants seems to significantly alter the feeding patterns and behavior of hummingbirds in several ways:
Increased Vigilance
Hummingbirds will be more cautious and alert when feeding in areas with more ant activity. They spend more time looking around and checking for ants before inserting their beaks into flowers.
Reduced Feeding Time
When hummingbirds do feed from flowers also visited by ants, they tend to feed for shorter durations. One study found hummingbirds would feed for only about half as much time on flowers with ants compared to ant-free flowers.
More Frequent Flower Switching
Hummingbirds will feed from multiple flower types intermittently when ants are present. By shifting between different flowers, they reduce their exposure to contaminated nectar and avoid depleting any single flower type.
Displacement from Preferred Feeding Sites
Areas with high densities of ants may prevent hummingbirds from feeding on their preferred flower species in those sites. The ants essentially displace hummingbirds from prime feeding patches.
Increased Energy Expenditure
When ants force hummingbirds to alter their feeding strategy and patterns, it likely requires greater energy expenditure. The birds burn extra calories searching for and shifting between less preferable, ant-free flowers. This negatively impacts their energetics.
How Hummingbirds Detect Ants
Hummingbirds have several methods for detecting the presence of ants on flowers:
Vision
Hummingbirds have excellent color vision and the ability to see rapid movements. This allows them to spot the crawling ants on flowers. They can visually scan a patch from a distance before approaching to feed.
Smell
Ants produce pheromones and other odor cues that hummingbirds may detect. Studies show hummingbirds rely heavily on smell to gather information about food sources.
Feedback from Past Experience
Like many animals, hummingbirds can learn from experience and recognize where they encountered ants previously. They may associate the sight, smell, or location of certain flowers with past ant encounters.
Ant Sounds
It’s possible hummingbirds can hear the high-pitched sounds and stridulations some ants make. Further research is needed on hummingbird hearing sensitivity.
Disturbance of Flower Parts
As ants move over and feed from flowers, they may shake or disturb flower petals and parts. Subtle movements of plant structures may alert hummingbirds to an ant presence before they even see the insects.
Impact of Ants and Hummingbird Interactions on Pollination
The interactions between ants, hummingbirds, and flowers also influence pollination:
Decreased Pollination from Hummingbird Avoidance
When hummingbirds avoid flowers due to ants, those flowers receive reduced pollination services. Many plants rely on hummingbirds as their main pollinators, so ant activity can disrupt that process.
Altered Pollen Transfer
Ants crawling over flowers may cause some pollen transfer. However, this is often less effective than hummingbird pollination for those flower species. Ant activity may reduce pollen quality.
Opportunistic Nectar Robbery by Ants
The nectar in many flowers has evolved specifically to attract and reward specialized pollinators like hummingbirds. Ants are often opportunistic nectar thieves that take nectar without providing useful pollination services.
Reduced Seed Production
With reduced pollination from hummingbirds avoiding ant-visited flowers, those plants likely produce fewer viable seeds for reproduction.
However, some ant species may protect plants from herbivores, so they can also provide some indirect benefits to plants they steal nectar from. The overall outcomes of these complex ecological interactions are still being researched.
Key Factors That Influence Hummingbird-Ant Interactions at Flowers
Ant Species
Not all ant species disrupt hummingbird feeding equally. Tiny, inconspicuous ants may go undetected. Large, aggressive ants likely deter more hummingbird visits. Differences in ant pheromones and nectar contamination levels also influence interactions.
Flower Characteristics
Nectar volume, flower shape, petal thickness, and other plant traits affect how much ant activity is tolerated. Some flowers may be more resilient to ant damage.
Nectar Dynamics
Nectar secretion rate, sugar concentrations, and regrowth intervals impact the degree of nectar depletion by ants. Rapidly replenished flowers can better withstand ant theft.
Timing of Ant Activity
Nocturnal ants that feed when hummingbirds are inactive may have less effect on pollinator visitation. Ant cycle timing matters.
Density of Ants and Hummingbirds
More hummingbirds competing for fewer ant-free flowers intensifies avoidance behaviors. Higher ant densities deter more pollinators.
Presence of Other Food Sources
Access to alternate feeding sites allows hummingbirds to more readily bypass ant-visited flowers when needed. Resource availability is key.
The complex, context-dependent nature of these interactions means outcomes vary across locations, seasons, and species involved. More field research in different ecosystems will provide greater insight into these relationships.
Conclusion
The consensus from multiple studies is that hummingbirds do tend to avoid feeding from flowers that also have ants present. Ants can be nectar thieves that deplete food sources and potentially contaminate the remaining nectar. Hummingbirds seem to visually identify ant-occupied flowers and preferentially choose alternative, cleaner flowers when available. However, hummingbirds may utilize ant-visited flowers when other options are limited or the payoff is high enough. Ant activity often disrupts pollination by deterring hummingbird visitation, sometimes reducing seed output. But outcomes depend on many ecological factors. Understanding the nuances of hummingbird feeding choices in response to ants provides broader insights into pollinator behaviors and plant-insect interactions. Going forward, further research across different environments will help elucidate the context dependencies and impacts of these important pollinator-ant relationships.
