Birds singing beautiful songs is a sure sign of spring. But as summer approaches, many birds become less vocal and eventually stop singing altogether. Why do birds stop singing in summer? There are several reasons for this behavioral change.
Breeding Season Ends
For many birds, singing is primarily a mating behavior. Males sing to attract females and defend territories during the breeding season. But once eggs are laid and chicks hatch, there is less need for prolonged singing. The breeding season ends and parent birds become focused on raising their young rather than advertising for new mates. Species like robins and cardinals nearly cease singing once their young have fledged and feeding activities take precedence.
Molting Occurs
Late summer brings the annual molt – when birds replace their feathers. Molting is an energy-intensive process that can negatively impact vocalization. Birds going through their molt often appear disheveled as they lose old feathers and grow new ones. Their energy is directed towards the physiological process of molting rather than behaviors like singing. Loss of wing and tail feathers during molt also impacts a bird’s ability to perform aerial displays associated with breeding songs.
Hot Weather Sets In
The heat of summer can also suppress birdsong. Just as extreme cold forces birds to conserve energy in winter, sweltering temperatures have a similar effect. Extended hot, humid weather makes singing more physiologically taxing. Birds will limit singing to save moisture and avoid overheating. Cooler morning and evening temperatures often bring more vocal activity in summer when birds seem to have more energy to devote to singing.
Territoriality Declines
Breeding season also brings high territorial behavior and boundary defense. But as nesting duties end, the need for frequent territory alerts also declines. Males are less motivated to sing long melodious songs proclaiming ownership of turf and warning off rivals. Short alarm calls may still be used to signal intruders, but longer warbling territorial proclamations become less necessary.
Hormone Levels Change
Singing frequency and intensity are influenced by testosterone levels in male birds. Testosterone drives breeding behaviors like singing. Research shows that testosterone levels peak during mate attraction and territory defense and then drop off when parenting duties begin. This hormonal shift leads to decreased vocal displays. Year-round territorial birds tend to maintain higher testosterone levels and more consistent singing through the summer compared to seasonal territorial breeders.
How Birds Change Their Singing Habits in Summer
The fact that most birds sing less in summer does not mean vocalizations cease altogether. Here are some common changes to singing habits once breeding ends:
Shorter Singing Bursts
Birds will still sing from time to time but cut back on the duration of songs. Brief melodious outbursts may be heard rather than extended belting. It takes less energy for a bird to pop out a short vocal ditty compared to singing enthusiastically for long periods. American robins provide a good example of a species that delivers shortened singing bouts in summer.
Dawn Chorus Only
Many birds confine the bulk of their singing to early morning in summer. The cool temperatures make dawn a better time to vocalize before the day heats up. Birds will participate in the dawn chorus, but then greatly curtail or even cease singing for the rest of the day. Cardinals and tufted titmice favor this pattern of singing only at first light.
Soft Warbling
The intensity and power of bird vocalizations also diminish in summer. Loud robust songs give way to soft gentle warbling. Chipping sparrows provide a good example of a species whose sharp melodious trills heard in spring become muted warbles by early summer. It does not take as much effort to produce subdued warbling.
Shorter Song Repertoire
Some species like northern mockingbirds have extensive song repertoires they fully utilize in spring. But summer singing is often limited to repeating just a few songs. Mockingbirds may sing dozens of unique songs in spring as they display the full breadth of their vocal abilities for potential mates. Their summer singing is comprised of only a handful of their most common songs repeated frequently.
No Song Variations
Many birds sing slightly different variations of their songs in spring. Females may prefer more complex songs with frequent variations. But in summer, males stick to singing a standard version of songs without modifications or improvisations. American goldfinches provide a good example of a species that loses much of its variable trill repertoire after breeding season.
Why Do Some Birds Continue Singing in Summer?
Although most birds reduce singing efforts after breeding, some species maintain persistent songs all summer long. Here are reasons why certain birds defy the norm of decreasing vocalizations in summer:
Attracting a Second Mate
Birds that lose a mate during breeding season may continue singing urgently through summer to attract a new partner. This helps increase their chances of raising a second brood. Mourning doves and eastern bluebirds are examples of birds that will immediately resume vigorous singing after losing a mate so they can find a replacement.
Young Males Practice Songs
Young male birds learn songs from adult male tutors. Young males may actively practice their developing songs all summer long even without a territorial purpose. Birds like northern cardinals maintain some song output through summer as young males work on mastering vocal skills.
Year-Round Territorial Species
Species that maintain year-round territories are very motivated to advertise ownership and ward off trespassers at all times. So they persist in regular singing through the summer. Birds like northern mockingbirds and Carolina wrens are vigilant defenders of year-round territories and continue purposeful singing through the summer months.
Non-Native Species
Introduced species brought to new regions may not follow the natural annual singing fluctuations in an area. For example, European starlings in North America continue singing year-round and do not display strong seasonal variations like most native North American species. Their breeding timeframe is not restricted by seasonal changes to the same degree.
Nesting Pairs Communicate
Mated birds may sing soft short songs to keep in contact with a partner working on a nearby nest. This is common in species where parents have unequal roles in nest building and incubating. The male may sing brief updates to convey his status and location to the female while she attends the nest.
Letting Nestlings Learn Songs
Adult birds sing near the nest so nestlings can listen and learn their species’ songs. This helps young birds memorize the vocalizations they will need to master as adults. American crows provide a good example of parents that regularly sing near nests containing young to facilitate song learning.
How Bird Song Differs Between Spring and Summer
Here is a summary of the major differences between typical singing behaviors of birds during the breeding season compared to summer:
Spring | Summer |
---|---|
Longer singing duration | Shorter singing bursts |
Earlier dawn chorus | Later, limited dawn chorus |
More frequent song bouts | Less frequent sporadic singing |
Lower latitude birds initiate singing earlier | Singing initiated when temperatures warm up |
More song types and variations | Smaller song repertoire with few variations |
Louder, higher pitched, and higher energy singing | Softer, lower pitched, lower energy singing |
Consistent singing throughout the day | Mostly early morning singing |
Maximizing song range to attract females | No need to attract mates |
Advertising territory ownership and warding off rivals | Reduced need for frequent territory alerts |
Young males mimic adults and practice songs | Young males actively develop vocal skills |
Notable Songbirds That Stop Singing in Summer
Here are some examples of common backyard birds that become much less vocal in summer compared to the active singing heard during spring:
American Robin
American robins fill spring mornings with loud flute-like melodies emanating from treetops. But they become nearly silent as summer approaches. Their short whistled outbursts are infrequent and subdued in summer.
Northern Cardinal
The whistles of northern cardinals are a constant background sound of spring as males call boldly and persistently. But summer brings fewer melodious interludes from males other than some soft chipping calls.
Tufted Titmouse
The variable whistles and trills of tufted titmice add lively animation to spring days. By summer, their morning tunes and harsh “peto” calls are much less conspicuous.
Chipping Sparrow
Chipping sparrows vocalize with their crisp rhythmic trills through spring. But summer finds these sparrows restricting singing to just early morning hours with longer breaks of silence.
Eastern Bluebird
The warbling songs and churring calls of eastern bluebirds are hallmarks of spring as males sing steadfastly. But they can become nearly voiceless in summer beyond an occasional soft chirp.
Dark-eyed Junco
Dark-eyed juncos perform a high-pitched trilling song in spring. But they rarely make this sound in summer beyond a few quiet drier trills.
Song Sparrow
Song sparrows live up to their name in spring when they sing loud elaborate melodies from perches. By mid-summer, their tunes are truncated to just brief snippets.
House Finch
The complex songs and calls of house finches fill the air in spring and highlight their musical abilities. In summer, long stretches can pass with no songs heard from males.
Black-capped Chickadee
Chickadees have a wide variety of whistles and chick-a-dee calls. But by summer, their vocalizations fade to mostly simple contact notes around feeders.
What Environmental Factors Influence Bird Singing?
In addition to seasonal hormonal shifts, weather and environmental factors can alter daily and seasonal singing patterns in birds. Here are some influences on singing:
Temperature
Low temperatures encourage more frequent singing to boost body heat. Hotter temperatures lead to reduced singing to avoid overheating and moisture loss. Cooler mornings prompt more singing.
Rainfall
Bouts of heavy rain cause birds to temporarily stop singing and seek shelter. Song rates increase again as conditions become drier. Lower humidity prompts more vocalizing.
Food Availability
Plentiful food resources provide birds with excess energy to devote to singing. Areas with higher food availability have higher song output compared to poorer habitat. Birds may migrate out of areas lacking sufficient food availability.
Territory Quality
Higher quality habitats with better nesting and shelter resources prompt males to sing more vigorously to claim prime real estate. Lower quality territories elicit less enthusiastic vocal displays.
Predators
Areas with more predators and threats cause birds to limit conspicuous singing to avoid attracting attention. Safer environments lead to bolder and steadier singing activity.
Parasites
Higher parasite loads place physiological burdens on birds that require more energy expenditure, reducing energy devoted to singing. Healthier individuals in prime condition sing more actively than infected birds.
Artificial Light
Excessive artificial light near habitat causes some species to start singing earlier before dawn since light levels simulate daybreak. This can alter natural seasonal singing cycles.
Noise Pollution
Noisy urban settings impede birds from hearing their own songs. Some birds increase singing efforts to be heard over noise pollution. Others simply abandon noisy spaces.
How Artificial Lighting Changes Bird Singing Patterns
Research shows that light pollution from excessive artificial lighting is altering the natural seasonal singing behaviors of some bird species:
Earlier Dawn Singing
Outdoor security lights, street lamps, and other light sources cause some birds to initiate dawn singing earlier than normal in the summer. This leads to more vocal activity in the predawn hours when birds would otherwise be silent.
Longer Singing Duration
The extra artificial light just before sunrise tricks birds into thinking the day is starting earlier. This results in prolonged singing duration into the late morning by birds near light sources. Their natural decrease in singing later in the day is disrupted.
Late Evening Singing
Bright lights on buildings, bridges, and parking lots fool birds into thinking sunset is later than it really is. Some species continue singing well into the night since darkness does not trigger a natural decrease in vocalizations.
Increased Predation Risk
Nocturnal predators find it easier to catch songbirds that are vocalizing outside of daylight hours near artificial lights. Night singing exposes birds to greater danger of predation they would normally avoid by being quiet at night.
Poor Sleep
Disrupted seasonal rhythms hinder birds from receiving sufficient uninterrupted sleep at night required for optimal health and breeding condition. Light pollution has been shown to negatively impact sleep and reproductive success.
Reduced Egg Production
Altered seasonal lighting exposure can negatively affect reproductive hormone pathways. Research on blackbirds found females nesting near street lights laid fewer eggs compared to birds nesting in darker areas.
Advancement of Egg Laying
The artificial extension of daylight hours shifts hormonal cycles and leads some birds to begin laying eggs earlier in the season. This risks increased chick mortality if food availability has not aligned with the earlier breeding.
Decline of Native Species
Light pollution allows some adaptive non-native species to capitalize on extended vocal activity. This gives invasive competitors an advantage over native birds that follow strict seasonal cycles not attuned to artificial lighting.
Conclusion
Birds rely on changes in day length as an important seasonal cue to shift singing habits and breeding behaviors. But artificial lights are now altering these patterns and creating risks. Being aware of these impacts may lead more communities to adopt smarter lighting policies that work with natural rhythms instead of disrupting them. Protecting vital seasonal cycles will help songbird populations thrive. The future of sustainable cities must be in sync with natural cycles, not opposed to them, if people hope to continue enjoying the songs of birds.