As a naked, blind hatchling transforms into a feathered juvenile, the young altricial bird approaches a pivotal event in its life leaving the nest. Departure from the nest and then from parental care increases a chick’s vulnerability to predators and the weather. During this time the chick’s mortality rate is high. After the first dangerous days have passed, however, the fledgling chick is safer than it would have been back in a vulnerable nest. Fledglings protect themselves if there is a warning call from their parents by staying still or by hiding. Camouflaging plumage along with Immobility combined can render chicks extremely difficult to find.
Nestling and Fledging
Technically speaking, the nestling period is the interval between hatching and departure from the nest,
Peregrine Falcons and the fledging period is the interval between hatching and flight. The nestling and fledging periods will be the same for altricial birds, like hummingbirds, but different in precocial and sub-precocial birds, which have short nestling and long fledging periods. “Fledging” is a term used to refer to the moment of departure by altricial birds even though the young birds only scramble and flutter for a few days before their first flight.
Do parents teach young ones foraging skills?
Sometimes birds learn some important foraging techniques from their parents. For example, the Common Ravens juvenile phase seems to be a highly exploratory and curious behavior that helps them learn both from both trial and error and their parents about which foods are edible. This innate tendency to approach novel environments or objects appears to be most frequently in birds that forage broadly on multiple different types of food. In addition, parents teach young ones how to hunt, a behavior found commonly in carnivores like raptors as they require complex skills to capture prey.
For example, parent Ospreys sequentially bring dead prey to their young offspring, then start to bring live but incapacitated prey, and as the young ones develop skills live prey that requires recapture. In Costa Rica, White‐fronted Nunbird parents holding a large insect conspicuously for their juvenile to practice snatching while in flight. The significance of learning to feed is instructed by local feeding traditions within a species; for example, Peregrine Falcons in New Mexico (USA) specialize in capturing bats as they emerge from their roosting caves.
Growth stages
Getting ready and leaving the nest
Long before they are ready to leave the nest or to fly, young birds develop essential strengths through exercise. Young pelicans jump up and down and flap their growing wings with increasingly effective strokes. Young hummingbirds anchor themselves not to take off grip nest fabric with their feet as they practice beating their new wings. When first airborne, some young birds respond to the new experience with astounding ability and control. Young Osprey on its first flight over a northern lake, flaps and wobbles uncertainly, loses altitude, and seems to splash into the lake. In the last possible moments, it flaps more effectively and gains altitude, climbing steadily and safely high above the lake. It then glides in circles and practices steering and control. Even more impressive are newly fledged Common Swifts, which spend their first night out of the nest on the wing.
Initial stages away from the nest:
Mobile young birds follow a tactic that reduces the strain on the parents by moving with their parents closer to good feeding grounds. The initial stages away from the nest are often heroic ones. One brood of Wood Ducks jumped two meters to the ground from their nest in a tree cavity and then followed their mother down a bluff and across a railroad track before swimming three-quarters of a mile across the Mississippi River to feeding grounds in good bottomland. More amazing always is the pair of Egyptian Geese that bred for several years on the roof of a building in Johannesburg, South Africa. After the chicks hatched, the female herded them toward the roof’s drain outlet, and after a little pushing and shoving, they fell three stories down the drainpipe at the curved end of the drain pipe.
Under more natural circumstances, precocial chicks that leave nests in tall trees or high cliffs must leap to the ground below, bouncing off soft earth if they are lucky or off jagged rocks if they are not. Torrent Ducks live in the dangerous fast-flowing water streams high in the South American Andes. To leave their nests in cliff crevices or holes above the streams, ducklings plunge as much as 20 meters into the turbulent water of the rocky streams below. Only rarely do they hurt themselves. Their lightweight, buoyancy, and downy cushioning protect them from severe impact.
statics of survival initial stages of leaving the nest:
Nevertheless, mortality in the first few weeks out of the nest is typically high and relentless, especially in the first days out of the nest. Only 19 percent of Hooded Warblers survived the 28-day fledgling period before independence, and fledglings’ day-to-day survival rate was lowest in the first four days once they left the nest. Predators take about 50 percent of fledgling Yellow-eyed Juncos incapable of extended flight in the initial nine-day risk period. Survival then improves for three weeks while parent juncos care for their mobile fledglings. With independence, however, comes a second episode of high mortality due to starvation. Newly separated young find insects inefficiently and slowly and spend nearly all day feeding. Approximately half of them die, most by starvation. These juveniles take about two weeks to develop essential foraging skills.
Factors that improve fledging survival
A fledgling’s chance of survival increases in proportion to its mass at fledging. In general, a young bird’s chances of survival increase with the state of its physical development when it leaves the nest.
This advanced development is the main advantage of longer nestling periods and aids in faster growth in altricial nestlings.
The food availability, the quality of parental care, the number of siblings competing for that, and the departure timing from the nest all affect a fledgling’s physical condition.
Other Development
Behavioral Growth and Development
Both heritage and experience affect the behavior of birds. This clarifies the past decade’s intense debates about whether a certain behavior is learned or innate. Behavioral patterns of birds change constantly from those derived completely from experience and those modified by experience. The embryonic growth patterns are linked to the period of incubation, for example, setting the stage for later cognitive abilities required for foraging innovation and social interactions. Both prolonged learning experiences and brief exposures to imprinting link a bird’s genetic heritage of nerves, bones, muscles, and hormones to its ambient and social environments.
Innate responses to particular color patterns or objects guide a chick’s food solicitation from its parents. Once they are physically capable, for example, hatchling Herring Gulls to receive food from parents it will peck at the red spot on the bill tip of a parent. The simple stimulation near the end of the bill is quite complicated. It includes several elements, such as shape and color contrast. Experimenting with the use of bill-like sticks with color-pattern on this species and with the Laughing Gull showed that the most effective stimulus for pecking was red or blue, with a nine-millimeter wide, elliptic rod, held vertically at the level of the young chick’s eye and moved horizontally 80 times a minute. The Laughing Gull chick’s accuracy in pecking increases as ages and has motor coordination, depth perception, and the capability to predict its parents occasionally. Older, chicks restrict their pecking to stimuli most similar to the adult.
Predator Recognition
How do baby birds avoid danger?
The natural escape responses of juveniles to predators are both born and learned. Household baby chickens innately avoid eating warning colors like the yellow and black of many caterpillars. They will then refine their choices with experience. Similarly, hand-raised Turquoise-browed Motmots are scared by colored sticks painted with red, black, and yellow bands since they look like coral snakes. Such a reaction is learned coral snakes are dangerous. Rather than learning to associate this color with danger by direct experience, birds are genetically predisposed to avoid the danger, and then they learn refinements. Hatchling Australian Brushturkeys like various other megapodes are independent once they emerge from the compost mound. They respond intrinsically to the alarm calls of songbirds by showing more alertness. They also react to wild predators by running or by crouching.
Knowing about predators is important. Naïve, young Great Tits fail to distinguish between a nonpredator and a predator, even though elder,
adults and wild-caught birds do so. In part, young birds by observing the mobbing behavior of other birds, learn to recognize predators or improve their recognition. Adults attack and scold owls and snakes that they discover. Immature birds quickly associate possible dangers with this commotion.
Imprinting parents
Imprinting is irreversible it is a special learning that takes place during a time period called the critical learning period. Something learned during this period persists. Imprinting determines habitat preferences and adult mate preferences. Imprinting also includes the prey-impaling behavior and the selection of nest materials and sites.
Successful captive propagation of endangered bird species requires careful attention to the early visual experiences of hand-reared chicks An early sensitive period enables young precocial birds to establish the critical concept of “parent,” on which their survival depends. The young of species that leave the nest shortly after hatching must learn to distinguish their parents from inanimate or inappropriate objects. Ducklings, for example, imprint most strongly on a moving and calling object when they are from 13 to 16 hours old. The objects that ducklings follow define their future acceptance of comrades and mates. They start with their parents.
The next stage in the behavioral development of a chick is to learn to differentiate its parents from other adults. Their parent’s visual appearance alone was a critical distinguishing factor. When exposed to different breeds of hens, baby chicks tend to follow the one that looks more like their mother, which they had imprinted initially.
A baby bird also imprints on a parent’s voice, one of the first sounds it hears, possibly even while it is in the egg. Common Murre chicks before hatching, exchange calls with their parents and while hatching they even recognize their parent’s voices.
Learning Some Essential Skills
After chicks leave their nest, they need to go through intense learning and practice essential survival skills, which include avoiding predators and foraging.
Fledglings of small passerines stay with their parents for two to three weeks after they left their nest.
In the Tropics, where long training also seems necessary to develop feeding skills, some young passerines for about 10 to 23 weeks stay with their parents.
Young terns and boobies rely on their parents for about as long as six months after they left the nest until they have mastered the skill of plunging after fish.
The post-fledging period is the last period of parent-offspring conflict. Fledglings should extend this period of parental care as long as possible. Parents, however, will encourage the independence of their young as soon as their investment is secure, which allows them to start incubating another clutch. In species like Montagu’s Harriers, parents terminate the post-fledging dependence by reducing the amount of food that they provide they do this, as soon as the fledglings’ flying and hunting skills improve.
In seasons of inadequate food availability and hunting becomes tougher, the fledglings try even harder to extend parental care.
Other essential skills also develop with social experience and age. Navigation and direction skills require the definition of goals and calibration of compasses.
Do birds play with their siblings?
Social skills and dominance also improve with age. Some birds play like Ravens, young crows, jackdaws, and their relatives, frequently play and even create elaborate games similar to “follow the leader” or “king of the mountain.” Exchange of sticks, stick balancing and manipulation, sometimes while upside down, and taking turns sliding down a smooth piece of wood in a cage are among the numerous games that these intelligent birds play.
Peregrine Falcons through playful practice and social interactions develop their hunting skills. They develop their hunting and flying skills through interactions when playing with their siblings. In aerial dogfights, they chase and dive at each other, called stooping, and roll over to grapple each other’s talons.