Altricial birds are a type of bird that hatch in an underdeveloped state and require extensive parental care after hatching. They are sometimes referred to as “nidicolous” birds as they spend an extended time in the nest before fledging. Altricial birds contrast with precocial birds, which are able to feed and move around on their own soon after hatching.
What are the characteristics of altricial birds?
There are several key characteristics that define altricial birds:
- Helpless at hatching – Altricial hatchlings are blind, naked, and completely dependent on their parents for food and warmth. They do not have the strength or coordination to stand, walk or feed themselves.
- Underdeveloped – The organs and systems of altricial birds are not fully developed at hatching. Their eyes are closed and their digestive system is incomplete.
- Extended nesting period – Altricial birds remain in the nest for an extended period, often several weeks, while their parents care for them. They do not fledge or leave the nest until their wings are fully developed.
- Delayed maturity – It takes time for altricial birds to mature after leaving the nest. They may still require parental care such as feeding and protection.
Some examples of traits specific to different altricial bird species include:
- Songbirds – blind, naked, dependent on parents
- Woodpeckers – helpless, requiring parental care
- Falcons – semi-altricial, leave nest at advanced stage
- Flamingos – dependent on crop milk from parents
- Penguins – fed regurgitated food by parents
Why are some birds altricial?
There are several evolutionary factors that help explain why some bird species are altricial:
- Faster population growth – Altricial birds can start breeding earlier as the chicks require less time to mature. This allows for rapid population growth.
- Increased brain development – The extended nesting period allows for greater brain development and learning while the parents provide for the young.
- Specialization benefits – Parental care allows each parent to specialize in roles such as protecting, incubating or gathering food.
- Habitat driven – Altricial development is favored in habitats where food availability fluctuates or parental care provides an advantage.
Additionally, some researchers hypothesize that altricial development enables birds to have lighter eggs, more eggs per clutch, and smaller bodies–all adaptations that optimize flight. The tradeoff is that altricial hatchlings are extremely vulnerable and dependent on dedicated parental care.
What kind of care do altricial birds need?
Altricial birds have specialized needs and require extensive parental investment to survive both in the nest and after fledging:
- Warmth – Altricial hatchlings cannot thermoregulate and rely on the body heat of the brooding parent, often the mother, for warmth.
- Food – Parents provide each chick with hundreds of meals per day, either by dropping food into the nest or by regurgitation.
- Protection – Altricial young are vulnerable to predators. Parent birds defend the nest and may mob or attack intruders.
- Developmental stimulation – Parent birds encourage motor skills and socialization through activities like wing-flapping and vocalizations.
Even after leaving the nest, altricial birds continue to depend on their parents for survival skills like identifying food, avoiding predators, migration routes, and social dynamics.
Comparison with precocial birds
Precocial and altricial development represent two extremes avian life history strategies. Here is a comparison:
| Trait | Precocial Birds | Altricial Birds |
|---|---|---|
| Maturity at hatching | Relatively mature, mobile, down covered | Helpless, naked, eyes closed |
| Early care needs | Able to leave nest shortly after hatching, can feed self | Dependent on parents for warmth, food, protection |
| Time in nest | Hours to days | Weeks to months |
| Examples | Ducks, chickens, quail, grouse | Songbirds, woodpeckers, crows, hawks |
As illustrated, precocial young are relatively mature and mobile from hatching and require less parental care overall. In contrast, altricial hatchlings are wholly dependent on dedicated care from both parents to survive and develop.
What are some examples of altricial birds?
Many common bird species are altricial, including:
- Songbirds – The vast majority of small perching birds like finches, warblers, sparrows.
- Crows and allies – Crows, ravens, magpies, jays.
- Nightjars – Nighthawks, whip-poor-wills.
- Kiwis – Flightless New Zealand bird.
- Parrots – Parakeets, cockatoos, macaws.
- Owls – Barn owls, snowy owls, burrowing owls.
- Woodpeckers and allies – Woodpeckers, toucans.
- Waterfowl – Ducks, geese, gulls, terns.
- Hawks and eagles – Bald eagles, red-tailed hawks.
- Herons – Great blue heron, egrets.
Many other common backyard or water birds are also altricial, highlighting just how widespread this developmental strategy is in birds.
Songbirds
The vast majority of small perching birds known as passerines, including finches, warblers, sparrows, swallows and larks employ an altricial development strategy. These hatchlings are born naked, blind, and dependent on their parents for warmth, food and protection. Parent passerines are well-adapted to rear altricial young, with adaptations like beak pouches for shuttling food back to the nest.
Crows
Crows, ravens, magpies and jays are incredibly intelligent birds that also demonstrate altricial development. They hatch helpless after about 18 days of incubation but are tended constantly by both parents. Young crows fledge at 25-30 days but continue to be fed by the adults for an extended period as they learn survival skills like identifying food and avoiding predators.
Woodpeckers
Woodpeckers are also altricial, hatching after about two weeks of incubation. The helpless hatchlings are brooded in the nest cavity and receive regurgitated food from both parents who visit the nest up to 400 times per day. After fledging, the young woodpeckers continue to roost and receive care in the nest cavity while honing their pecking skills.
Conclusion
Altricial birds represent a unique avian life history strategy characterized by a high degree of offspring helplessness and dependence on parental care. However, this altricial development confers many benefits that allow species to thrive, particularly the ability to breed rapidly. Recognizing which common backyard, water and wild birds are altricial provides insight into their breeding ecology and the amazing devotion they show as parents.
