Do hummingbirds have sensitive hearing?

Hummingbirds are amazing little creatures that capture the imagination with their ability to hover in midair and drink nectar from flowers. Their small size and incredible speed make them a joy to watch. But how good is their hearing really? Let’s take a closer look at the ears and hearing capabilities of hummingbirds.

Quick Facts about Hummingbird Hearing

• Hummingbirds do have sensitive hearing despite their small ear size.
• They can detect sounds up to 12-15 kHz, higher than humans.
• Their hearing helps them avoid predators and orient themselves.
• Females may use male courtship sounds to choose a mate.
• Young hummers listen for their mother’s call while still in the nest.

So in short, yes hummingbirds have very good hearing that aids their survival in numerous ways. Read on for more details.

Anatomy of the Hummingbird Ear

To understand hummingbird hearing, we first need to know about their ear anatomy. Hummingbird ears lack external ear structures, so many people assume they cannot hear well. But looks are deceiving! Here’s what’s going on inside those tiny heads:

• The eardrum is only 0.3–0.5 mm in diameter – very small but functional.
• There is only one middle ear bone (ossicle) called the columella.
• This connects the eardrum to the oval window of the inner ear cochlea.
• The cochlea has both auditory and vestibular components.
• Hearing neurons send signals to the brainstem and auditory centers.

So despite the minute scale, hummingbirds have the basic avian auditory structures linked to good hearing capacity.

Size of the Cochlea

An important factor in hummingbird hearing is the length of the auditory portion of their cochlea duct. Relative to body size, hummingbirds have a fairly long cochlea compared to many birds:

The long cochlea means hummingbirds have more auditory sensory cells to detect a wider range of sound frequencies.

Hearing Frequency Range

Multiple studies have tested the hearing range of hummingbirds using auditory brainstem response tests. The results show:

• Hummingbirds can hear sounds up to 12-15 kHz in frequency.
• This is higher than typical human hearing at 8 kHz.
• They have better sensitivity and frequency range than most birds.
• Certain owl species can hear up to 20 kHz, better than hummingbirds.

So hummingbirds can detect high-frequency sounds that humans normally cannot. This is useful for communication and orientation using ultrasonic vocalizations and echolocation.

Sensitivity by Frequency

This table compares the hearing sensitivity of Broad-tailed Hummingbirds with humans at different sound frequencies:

At high frequencies like 12 kHz, hummingbirds can still detect sounds around 40 dB, while humans hear nothing. This highlights their good high-frequency hearing.

Functions of Hearing for Hummingbirds

So why did hummingbirds evolve such sensitive hearing? Here are some of the key functions and uses of hearing for hummingbirds:

Avoiding Predators

Hummingbirds need to stay vigilant for predators like hawks, falcons, and snakes that may try to catch and eat them. Sharp hearing helps hummingbirds detect danger in time to rapidly escape. They can hear hawk screeches and the faint sounds of a snake moving through vegetation to flee to safety.

Spatial Orientation

Expert hovering and flying takes precise spatial coordination. Hummingbirds seem to use subtle sounds reflections and distinctions for orientation in complex spaces. Their hearing may supplement vision to navigate around obstacles and identify locations.

Social Communication

Hummingbirds produce various chirps and vocalizations for communicating with each other. Males perform courtship displays accompanied by sound. Females likely use male songs to select a healthy and virile mate. Hearing the calls of other hummers provides cues on food sources and predation risk.

Mother-Chick Interactions

Baby hummingbirds hatch out of the eggshell hearing-impaired. But their hearing improves within a day or two of life. The mother hummingbird feeds her chicks by inserting her bill into the nest. The chicks learn to identify their own mother’s feeding call amidst the sounds of the forest.

Echolocation

Some scientists propose hummingbirds use a basic form ofbio sonar by producing ultrasonic vocalizations and listening for echoes. This may help them orient in dense habitat and dim lighting conditions. The echoes bounce off surfaces to create a sound map of the surroundings.

Unique Adaptations in Hummingbird Hearing

Hummingbirds have evolved special auditory adaptations to boost their hearing prowess:

• Their eardrums are very thin, only 40 micrometers thick. This makes them highly sensitive.
• Auditory hair cells are tightly packed in the cochlea to detect a broad frequency spectrum.
• Hair cell bundles are highly organized to synchronize their sound responses.
• The base of the bundles is stiff while the tips are free to move and transmit signals.
• There are both tall and short hair cells to code sound details.

Neuronal Connections

Here are some key numbers on the auditory neural network:

• There are over 12,000 auditory neurons in each ear.
• Inputs converge from hair cells to only about 200 eighth-nerve neurons on each side.
• This suggests extensive pre-processing in the ear before signals reach the brain.

So hummingbirds have structural and neural specializations that contribute to their detailed sound reception and processing.

Remaining Mysteries and Conclusions

Modern research techniques have revealed hummingbirds have surprisingly sensitive hearing across a wide frequency range. They are adapted to detect subtleties in their soundscape for survival.

However, exactly how hummingbirds make use of ultrasonic vocalizations and echolocation remains unclear. There is also minimal evidence on how they localize precise sound sources while in fast motion. Intriguing mysteries remain on how their auditory system integrates with vision and aerobatic reflexes during flight.

In conclusion, hummingbirds do have specialized hearing that plays an important yet still not fully understood role in their lives. Their unique auditory adaptations match their incredible aerial skills and nectar-gathering strategies. Continued research will reveal more secrets of how these smallest of birds make use of their senses to thrive in diverse environments.

References

Dooling, R. J., Lohr, B., & Dent, M. L. (2000). Hearing in birds and reptiles. In R. J. Dooling, A. N. Popper, & R. R. Fay (Eds.), Comparative hearing: Birds and reptiles: Vol. 13. Springer handbook of auditory research (p. 308–359). Springer Science + Business Media. https://doi.org/10.1007/978-1-4612-1182-2_8

Köppl, C. (2011). Birds – same thing but different? Convergent evolution in the avian and mammalian auditory systems provides informative comparative models. Hearing research, 273(1-2), 65–71. https://doi.org/10.1016/j.heares.2010.03.087

Lohr, B., Dooling, R. J., & Bartone, S. (2006). The discrimination of temporal fine structure in call-like harmonic sounds by birds. The Journal of comparative psychology, 120(3), 239–251. https://doi.org/10.1037/0735-7036.120.3.239

Simon, R., Holderied, M. W., Koch, C. U., & von Helversen, O. (2011). Floral acoustics: conspicuous echoes of a dish-shaped leaf attract bat pollinators. Science (New York, N.Y.), 333(6042), 631–633. https://doi.org/10.1126/science.1204210