Birds make all kinds of noises from chirps to squawks to songs, but some of their vocalizations can be quite loud and alarming to humans. Screaming or shrieking is common among certain bird species and serves a variety of purposes. Understanding why birds scream can provide insight into avian communication, behavior, and evolution.
What is a Bird Scream?
A bird scream refers to a loud, piercing call. The sound is often abrupt, harsh and high-pitched. This differs from a bird song, which tends to be more melodious and complex. Screams are simple, direct vocalizations used to quickly get across specific messages.
Some examples of birds well-known for their screaming abilities include blue jays, Swainson’s hawks, bald eagles and parrots. However, many common backyard birds like crows, grackles, starlings, magpies, and mourning doves may scream on occasion as well. Even small songbirds like chickadees and finches can produce alarm screams.
Reasons Birds Scream
Birds scream for the following reasons:
- Territorial warnings
- Alarm calls
- Begging calls from offspring
- Flock communication
- Mating calls
- Predator mobbing
Let’s explore each of these scream types and what they mean.
Territorial Screams
Many birds use screaming as a territorial display. Loud vocalizations communicate a claim on resources and mates. Resident birds scream to signal possession of a nest site or feeding ground and to repel intruders.
Common territorial screamers include blue jays, northern flickers, red-winged blackbirds and barn owls. The familiar “caw caw” of American crows is a territorial scream. Horned owls announce possession of a nest cavity with their iconic hoots.
While screaming may deter trespassers, it also attracts mates. Males seek to advise females of bountiful resources within their territory. The intensity and persistence of territorial screams signifies the male’s fitness. Females often prefer males with the strongest territorial screams.
Screaming Matches
Competing males will scream back and forth in intense contests. This screaming battle advertises each bird’s vigorous health and fighting abilities. The bird able to sustain the loudest, longest screaming bout often wins the turf. Even females may join in cacophonous screaming matches prior to mating.
Screaming is energetically expensive, so the bird able to scream the most demonstrates superior strength and endurance. Persistent screamers also show their willingness to invest maximum effort in defending resources necessary for breeding.
Alarm Screams
Birds produce alarm calls to warn others of potential danger. These screams signal predators or threats and broadcast an urgent message to take cover. From a survival standpoint, loud alarm screams quickly relay critical information.
Many social bird groups use alarm calls. Flocks, families and breeding pairs all benefit from cooperative screaming that relays imminent risk. Crows, jays, blackbirds, chickadees, finches and swallows demonstrate well-known alarm scream behaviors.
Predator Alerts
Birds identify specific predators through variations in their alarm screams. Research shows that birds even respond appropriately to recorded alarm calls for different predators. For example, crows produce a rapid staccato scream for hawk alarms compared to a lower stretched call for owl alerts.
Unique vocalizations for each predator help other birds respond correctly without directly observing the threat. Distinct screams warn if evasive maneuvering in the air is needed versus hiding in dense cover. Some birds even identify predator size based on call pitch or frequency.
Screaming Frenzies
The sight of a predator often triggers an eruption of screams as multiple birds relay the danger. Large noisy flocks amplify alarm calls and create confusion to overwhelm a predator. Mass unity provides security.
Mobbing predators is another reason birds congregate into screaming frenzies. Swarming a predator may drive it from the area or signal where it hides. This allows other birds to avoid the threat. Diving at predators also displays the risk of group retaliation if attacks persist.
Offspring Begging Calls
Baby birds beg for food with loud screams that are impossible for parents to ignore. The screams stimulate regurgitation and delivery of meals by parents. Begging screams provide honest signals of chicks’ hunger levels and health.
Honest Hunger Signals
Research shows that begging intensity indicates a chick’s energy reserves and need. Louder, quicker screams reflect increased hunger. Parents respond by providing more food. Honest signaling ensures adequate resources for the healthiest, strongest chicks.
The location and persistence of screams also signal chicks most at risk or easiest for parents to reach. Begging calls taper off when chicks approach satiation. This prevents waste and overfeeding.
Increased Urgency
As chicks get older, their screams take on a more urgent or exaggerated quality. Parents become somewhat desensitized. Increased scream urgency captures parental attention for continued care.
Higher pituitary levels in screaming chicks stimulate parental instincts. Loud begging literally alters parental hormone levels and brain activity to promote nurturing responses.
Flock Communication
Flocks scream to stay in contact and coordinate activities. Vocal cues keep groups unified while foraging and migrating. Flock screams also relay important events like food sources or predators.
Constant screaming provides self-reassurance that social bonds persist within bustling activity. Vocalizations help maintain flock cohesion, especially near predators. Familiar screams signify group belonging too.
Screaming as Bonding
Roosting flocks end their days with communal screaming. In the evening, groups of crows all scream together before settling down. This group bonding behavior is known as corvid cacophony, though many birds indulge in cacophonous screaming to strengthen social ties.
Duet and chorus screaming also helps pairs or colonies bond when breeding. Performing the same screams breeds affiliation. The cooperation needed for coordinated vocal bouts cements mutual commitment.
Mating Screams
Screaming plays a vital role in avian courtship. Potential mates advertise themselves through signature screams or duets. Synchronized screaming fosters pair bonding.
Performances of Fitness
Loud vocal performances demonstrate a bird’s cardiovascular fitness. The ability to sustain screaming requires healthy lungs and endurance. Persistent screaming also indicates sufficient energy reserves for breeding.
Mate choices rely partially on the intensity of screams. Strong sustained screaming shows off the best cardio, strength and health needed to survive the demands of reproduction.
Duetting Displays
Paired birds will vocalize together in complex duets. Partners demonstrate cooperation, coordination and compatibility through tightly integrated duetting screams. The broader the repertoire of cohesive duet types a pair can perform, the stronger their bond.
Great horned owls are one of the most familiar duetting birds. The female’s higher pitched hoots harmonize with the male’s deeper hoots in complex duets. Most songbirds also duet with mates. Roosting flocks may perform group screeching contests, akin to singing competition shows.
Predator Mobbing
Birds gang up on predators through mobbing. This mob harassment includes repeated dive bombing while screaming loudly. The goal is to annoy and upset dangerous enemies.
Mobbing may deter predators from lingering near a nest or signals a predator’s location to the rest of the flock. It also displays a squadron of defenders willing to counter any attacks. Swallows aggressively mob predators near their mud nest colonies.
Heroic Self-sacrifice?
Mobbing seems to contradict the self-preservation function of alarm screams. Why risk confronting predators? Some suggest mobbing birds are heroic altruists willing to sacrifice themselves to protect others.
But mobbing likely provides hidden benefits. Mobbers gain intelligence on predator numbers, location and reactions. Predators too associate mobbing risks with attacks on certain sites. Harassing predators is also good practice.
Safety in Numbers
While mobbing seems high risk, a squadron of screaming dive bombers reduces risks to any single bird. And the most aggressive mob leaders tend to be the healthiest birds who can quickly evade predators. Mobbing is just another form of cooperative, communal risk reduction.
There is safety in numbers. Along with distressing predators, mobbing rallies reinforcements to the screaming throng. United, ardent screaming also empowers the birds psychologically.
Conclusion
Birds scream for many adaptive reasons. While alarming to humans, avian screaming is just a critical form of communication between birds. Loud vocalizations quickly convey urgent and important information related to territory, predators, offspring, bonding and harassment. Understanding the varied functions and contexts of bird screaming provides deeper insight into central needs for survival and reproduction. The next time birds erupt in cacophonous screams, listen closely rather than recoil. Their screams are telling an intricate story.
| Scream Function | Context | Examples |
|---|---|---|
| Territorial Warning | Repel intruders and attract mates | Blue jays, flickers, crows |
| Alarm Call | Warn of predators | Crows, chickadees, finches |
| Begging Call | Signal hunger to parents | Baby birds of all species |
| Flock Communication | Maintain contact and cohesion | Roosting flocks like crows |
| Mating Call | Attract mates and duet | Great horned owls, songbirds |
| Mobbing | Harass predators | Swallows, cooperative flocks |
