If you’ve ever wondered why birds are singing early in the morning but stop chirping later in the day, you’re not alone. The rhythms of bird vocalizations provide clues into avian biology and behavior.
If you’re short on time, here’s a quick answer to your question: Birds generally stop singing in the late morning or early afternoon when territories have been established and mating is over. Their hormones, metabolism, and energy levels fluctuate over the course of a day, influencing their urge to sing.
In this article, we’ll explore the fascinating science behind why and when birds stop their melodious trilling and chirping.
The Role of Bird Song
Defining Territories
Bird songs play a vital role in defining and protecting territories (Audubon). Songs mark the boundaries of a bird’s territory, warning rival males to stay away. This territorial signaling helps birds space themselves out to reduce competition for resources like food, nesting sites, and mates.
Amazingly, some species can recognize their neighbors by song alone and will avoid overlapping territories. Songs reach farther than visual displays in dense habitat, so acoustic signaling is often more effective than visual cues.
This allows birds to stake their claims over larger areas than they could using sight alone. Bird song helps maintain territory boundaries without dangerous physical confrontations.
Attracting Mates
Bird songs also function to attract mates (All About Birds). Males often sing to court females, demonstrating the quality of their genes through vocal skill and endurance. More elaborate songs can indicate better fitness, so females may preferentially choose males with complex songs.
In some species, pairs even sing coordinated duets to strengthen pair bonding. And birds with the largest repertoire of song types are sometimes preferred. For example, Marsh Wrens may mimic other species to seem more attractive.
So learning new songs takes effort but can really pay off with the ladies!
Signaling Danger
In addition to territory defense and courtship, birds use alarm calls to warn each other of danger (ScienceDaily). These mobbing calls recruit others to help drive intruders away or distract predators. Roosters are a familiar example, crowing at the first sight of a threat.
And chickadees have a complex system of alarm calls indicating the type of predator and level of danger. Their “chick-a-dee” mobbing calls can communicate fine details like size, speed, and threat. Other small passerines join these attacks, benefiting from their early warning.
So alarm calls provide a cooperative defense strategy against predators. Pretty impressive for a few short tweets!
Hormones and Singing
Testosterone Triggers Singing
Testosterone is the primary hormone that triggers birdsong in male birds. During breeding season, testosterone levels increase dramatically, triggering changes in the size of song control nuclei in the brain and activating complex vocalizations and courtship displays.
Testosterone stimulates singing by acting on androgen receptors in brain regions like the hypothalamus and song control nuclei. Recent research has even found testosterone receptors within vocal muscles themselves, allowing fine motor control of song.
Thus, testosterone coordinates brain and body for the complex task of birdsong.
Estrogen and Progesterone Affect Song Quality
While testosterone initiates singing behavior in male birds, other hormones like estrogen and progesterone help modulate song quality. Female birds have higher levels of estrogen and progesterone, which act on song control regions of the brain.
Research shows that blocking estrogen receptors in male zebra finch brains causes their song syntax to degrade. Furthermore, artificially increasing estrogen and progesterone levels in male birds causes their songs to sound more stereotyped and repetitive.
Therefore, estrogen and progesterone fine-tune male birdsong and reinforce proper syntax. This effect may help attract choosy females looking for males with robust and complex songs during courtship.
Corticosterone Indicates Stress
Corticosterone is a hormone associated with stress and arousal in birds. Prolonged elevated corticosterone suppresses reproductive behaviors like courtship displays and mating in birds. Studies measuring corticosterone levels before and after singing find that birdsong briefly lowers corticosterone levels, reducing stress.
However, severe stress and elevated corticosterone can impair song control circuitry in the brain. This causes abnormal repetitive vocalizations called “long calls” instead of organized birdsong. So monitoring corticosterone levels through non-invasive droppings analysis may indicate birds enduring chronic stressors like habitat loss or pollution.
Circadian Rhythms and Metabolism
Following the Biological Clock
Birds, like humans, have an internal “biological clock” that regulates their circadian rhythms over a roughly 24-hour cycle. This clock controls body temperature, hormone levels, sleep patterns, and other biological activities – including birdsong production.
Songbirds tend to be most active in singing in the early morning when hormone levels peak.
Sing Early, Rest Later
Many songbirds rise before dawn to belt out their melodious tunes at first light. But as the day wears on and their energy reserves drop, they sing less and spend more time resting to conserve calories.
One study found that nuthatches decrease singing time from almost 90% of daylight hours to just 10% over the course of the day.
Energy Reserves Drop Over the Day
Like human athletes, birds burn through a tremendous amount of energy while singing. Give a songbird unlimited food, and it will sing its heart out from dawn to dusk. But in the wild, birds must balance singing time against the need to replenish energy stores by hunting and foraging for food.
As daylight hours progress, most songbirds grow hungrier and their lipid and glycogen energy reserves drop. With less fuel in the tank, they simply can’t afford to sing as often. Saving their voices becomes a survival necessity so that they can resume chorusing at dawn the next day.
Environmental Factors
Light and Darkness
Light and darkness play a key role in regulating birdsong. Most birds sing during the day, with dawn and dusk choruses being especially prominent. This is because lighting conditions influence hormone levels and other physiological factors that control song production. Here are some details:
- Increasing light triggers hormonal changes that stimulate singing in many bird species. Melatonin levels drop while testosterone rises, activating song control centers in the brain.
- As light fades at dusk, melatonin begins rising again, eventually inhibiting singing behavior. This causes the evening chorus to dissipate.
- Artificial lighting can confuse birds’ circadian rhythms. It may cause them to start singing earlier before dawn or continue later into the evening.
- Some birds do sing at night, like nightjars or mockingbirds. But night singing is rare overall due to low light conditions.
In short, most birds sing during the brighter hours between dawn and dusk. Their singing is cued by changes in hormone levels that are regulated by daily light/dark cycles. Artificial lighting can disrupt these natural patterns.
Temperature Extremes
Temperature extremes can also impact birdsong production. Here’s an overview:
- Low temperatures – Cold weather causes birds’ metabolisms to slow down. This makes it harder to sing, as song production requires high metabolic activity. Many birds sing less in winter or stop singing altogether if it gets too cold.
- High temperatures – Heat stresses birds out, which may suppress singing. However, some species sing more frequently to signal distress or keep in touch when scattered by heat.
- Humidity – Moist air helps maintain vocal tissue health. But excessive humidity impedes heat dissipation during singing, potentially causing overheating. Low humidity can dry out vocal membranes, making songs hoarse.
In moderation, warmer temperatures with adequate humidity are ideal for birdsong. But temperature extremes force birds to alter or cease singing to conserve energy and avoid physiological strain.
Noise Pollution
Excess anthropogenic noise pollution makes it challenging for birds to communicate through song. They have to adjust their singing behavior in noisy environments. Some patterns include:
- Singing louder to be heard over background noise.
- Pitching songs higher to stand out from lower-frequency ambient noise.
- Singing at different times to avoid peak noise periods.
- Changing song structure to include more repetitions.
- Abandoning song type diversity for simpler, repetitive songs.
- Changing the frequency of singing, either increasing or decreasing depending on context.
While some birds can adapt to noise pollution, chronic exposure may impair mate attraction, breeding success, and territorial defense. It can also cause chronic stress with long-term health impacts. Minimizing noise disruption of natural soundscapes benefits birdsong and avian communities.
When Do Specific Birds Stop Singing?
Dawn Chorus Fades Away
The melodious singing of birds that marks the start of a new day begins to fade as daylight emerges. Most songbirds sing the loudest and most enthusiastically around dawn because it is important territory defending time and to attract potential mates.
Their cheerful chorus will die down after an hour or two of lively vocalizations once they have established boundaries and caught the attention of partners.
Night Singers Stop at Dawn
While most birds sing during the day, some prefer belting out their tunes under the cloak of night. Species like nightjars, owls, frogmouths, and some thrushes tend to sing after dusk when competing daytime birds have settled down.
Their nocturnal notes are vital for defending territories and mating in low light conditions. But even nighttime crooners wrap up vocal activity at the break of dawn and rest their voice boxes during daylight.
Differences Between Species
Not all birds are vocal dawn risers or late night chatterboxes. Some songbird species like larks continue singing intermittently all day long. Others may have multiple peak singing times depending on factors like mating status, competition levels, and seasonal changes.
Migratory birds tend to sing the most during springtime breeding while birds defending winter territories chirp more consistently all season long. When food is plentiful, songs may temporarily subside across a range of species as they focus more on feasting than fluting!
Conclusion
Bird vocalizations serve important purposes like defending territories and attracting mates. However, singing requires energy so birds limit calling and singing to certain times of day when it’s most needed.
Their hormones, circadian rhythms, energy reserves, and environment all influence when an individual bird stays silent or bursts into song. Understanding when birds stop singing provides fascinating insight into avian biology while allowing us to appreciate the complex behaviors of our feathered friends.
