Hummingbirds have an incredible ability to detect when the nectar they are feeding on has gone bad or sour. Their sense of taste and smell allows them to avoid spoiled nectar that could make them sick. Here’s an overview of how hummingbirds know when nectar is no longer fresh and safe to drink.
Hummingbirds can taste sour and bitter flavors
Hummingbirds have taste receptors on their tongues that allow them to detect sour, bitter, sweet, and umami flavors. When nectar starts to ferment and turn alcoholic, the sugars break down and the nectar takes on a sour or bitter taste. Hummingbirds are very sensitive to these tastes and will reject any nectar that has even a slight sour or bitter flavor.
Research has found that hummingbirds have a high density of taste buds compared to other birds. One study found that hummingbirds have around 1,100 taste buds compared to chickens which only have around 24. Their tongues also have grooves and fringes which may help them detect subtle taste differences.
This acute sense of taste protects hummingbirds from ingesting nectar that could expose them to toxins or make them sick. Even a small amount of spoiled nectar could be problematic for hummingbirds given their high metabolism.
Their sense of smell also kicks in
In addition to taste, hummingbirds also rely on their sense of smell to avoid rancid nectar. As nectar ferments, it gives off aromatic compounds that act as warning cues to hummingbirds. They quickly learn to associate these smells with nectar that will not be safe or provide nutritional value.
Researchers have discovered that hummingbirds have excellent odor detection and can learn to recognize the scent of sweet, fresh nectar versus spoiled nectar. They not only use sight to locate flowers, but smell probably helps lead them to the best nectar sources.
They will inspect nectar closely
Hummingbirds have good vision that allows them to inspect nectar quality up close. They can see color changes or debris in old nectar that might make it less palatable. You may see a hummingbird approach and hover near a flower to get a good look at the nectar before deciding to feed.
Interestingly, hummingbirds can also assess nectar quality just by looking at the age and condition of the flower itself. Older, wilted flowers often have lower quality or negligible amounts of nectar. Hummingbirds learn to target fresh, healthy flowers and ignore ones that are past their prime.
They remember flower locations and nectar quality
Research demonstrates hummingbirds have excellent memories when it comes to rewarding flower locations and nectar quality. Once they taste bad nectar at a particular flower or feeding station, they will avoid returning to that location.
Hummingbirds will also track nectar production cycles. If a flower previously had spoiled nectar, a hummingbird will remember that and temporarily avoid the flower until the nectar regenerates.
This ability to recall information about flowers and nectar quality allows hummingbirds to more efficiently find and feed on the highest quality nectar in their environment.
How does nectar go bad?
Nectar is essentially a mixture of sugars and water produced by plants. It has some natural antifungal and antibacterial properties when freshly made by the plant. However, nectar can spoil over time due to microbial activity.
Yeasts and bacteria are the main microbes that ferment and degrade nectar. These microorganisms break down the sugars in nectar and change its chemical composition. As a result, the nectar takes on a sour, bitter, or rancid taste and smell.
Nectar in hummingbird feeders can go bad within 2-4 days, especially in warm weather. The sugary mixture is an ideal breeding ground for microbes. Keeping feeders extremely clean and changing nectar frequently prevents buildup of microbes.
In natural settings, certain flowers may have antimicrobial compounds in their nectar to slow microbial growth. However, nectar in most flowers will eventually degrade over time.
Signs that indicate nectar has gone bad
Here are some signs that the nectar in a flower or feeder has spoiled and should be replaced:
- Cloudy appearance
- Layer of scum or mould on surface
- Sour or bitter smell
- Fermented odor like wine or vinegar
- Carbonated bubbles in nectar
- Change from clear to brown/murky color
Hummingbirds will avoid nectar at the first hints of spoilage, so we may not observe them actually drinking visibly contaminated nectar.
Do all hummingbirds avoid bad nectar?
Most research shows that all hummingbird species studied exhibit an ability to discriminate against poor quality or rancid nectar. However, younger hummingbirds may be more prone to sampling spoiled nectar than mature adults.
One study found that younger hummingbird fledglings were more likely to feed on fermented nectar than adult hummingbirds. The adults seemed to have learned to avoid anything with a fermented odor.
This suggests that some level of learning over time may reinforce hummingbirds’ avoidance of bad nectar. Young hummingbirds may need to experience an upset stomach from rotten nectar before they refine their foraging skills.
How else do hummingbirds avoid bad nectar?
In addition to taste, smell, vision, and memory, hummingbirds may use other strategies to avoid low quality nectar:
- Watching the feeding behaviors of other hummingbirds. If other hummingbirds are avoiding a particular flower, they may follow suit.
- Sampling just a small amount of unfamiliar nectar sources before drinking more. This allows them to taste test new flowers.
- Favoring flowers that are more vertically oriented. Research indicates this may help nectar avoid microbial contamination.
- Targeting flowers in sunlight over shade. Sun exposure helps keep nectar from developing mould.
Hummingbirds are vigilant about seeking out the best quality nectar thanks to their specialized senses and foraging behaviors.
Do hummingbirds ever get sick from bad nectar?
While hummingbirds work hard to avoid rancid nectar, they may occasionally ingest some by accident before tasting that it has spoiled. This can result in them becoming ill.
Symptoms that a hummingbird may have eaten bad nectar include:
- Lethargy or weakness
- Not moving around actively
- Ruffled feathers
- Tail bobbing
- Staggering or loss of balance
If a hummingbird becomes sick from ingesting fermented nectar, the best chance of recovery is taking it to a wildlife rehabilitation center. With supportive care, they can usually recover and be released back to the wild.
Key Takeaways
Hummingbirds have specialized adaptations to detect when nectar has gone bad. By relying on their keen senses of taste, smell, sight, and memory, hummingbirds can carefully avoid rancid nectar that would make them ill. While young hummingbirds may occasionally sample bad nectar by accident before learning to avoid it, most adult hummingbirds are excellent at discerning fresh, sweet nectar from foul spoiled nectar.
Conclusion
Hummingbirds have evolved remarkable physiological and behavioral tools to pinpoint the best quality nectar to fuel their high-energy lifestyles. Their ability to discriminate against anything even slightly fermented or rancid helps hummingbirds thrive among the flowers and feeders they visit. Understanding hummingbirds’ extraordinary nectar quality detection helps us appreciate the nuances of their foraging strategy and motivation for seeking out particular flowers and feeders.
