January/February 2026

8 – Purebred PIGEON Birds are classified into two large groups depending on whether their mode of development is altricial or precocial. Altricial birds hatch at an early stage of development and are incapable of moving around on their own soon after hatch- ing. Precocial birds hatch at a later stage of development and are capable of moving around on their own soon after hatch- ing. Ligon and Burt determined that 8890 of the 9993 extant species of birds (88%) have altricial development. Pigeons are altricial birds. THE ALTRICIAL-PRECOCIAL SPECTRUM Actually, the developmental modes of birds occur along a continuum from extremely altricial to extremely precocial. Four distinct patterns have been identified on this continuum. • Altricial: Hatched with eyes closed, with no down, incapable of leaving the nest, and fed by the parents. Exam- ples: all passerine birds • Semi-altricial: Covered with down, incapable of leaving the nest, and fed by the parents. Examples: hawks, which hatch with eyes open; and owls, which hatch with eyes closed • Semi-precocial: Hatched with eyes open, covered with down, and capable of leaving the nest soon after hatch- ing but remain at the nest and are fed by the parents. Exam- ples: gulls and terns • Precocial: Hatched with eyes open, covered with down, and leave the nest within two days. Examples: ducks, which follow their parents but find their own food; and game birds, which follow their parents and are shown food Pigeons are altricial birds. But more specifically, they are semi-altricial birds. They hatch with eyes closed and with down. Pigeon babies are blind but not bald. SEMI-ALTRICIAL PIGEONS The relative presence of natal down is a reliable indi- cator of where a bird species falls on the altricial-precocial spectrum. Precocial chicks, such as baby chickens, have the most natal down. The semi-altricial hatchlings of pigeons, which are covered with a yellowish or whitish down, have less down than precocial chicks but more down than altricial hatchlings. Like baby owls, pigeon squabs hatch with their eyes closed. And like other altricial birds, pigeons feed their babies in the nest. Pigeon parents differ from other altricial birds, however, by feeding crop milk to their chicks rather than high-protein animal foodstuffs. PROTEIN AND PREDATION Why do birds have these different modes of develop- ment? They appear to be different ways of dealing with two biological imperatives: the need for protein and the avoid- ance of predators. Females of precocial species, such as chickens, require a protein-rich diet before laying to support the greater in-egg development of precocial embryos. They invest energy in heavier eggs with larger yolks and more calories, but they benefit later from more independent chicks that feed themselves. On the other hand, altricial birds lay smaller eggs with smaller yolks and smaller energy demands on the female. She expends her energy in raising her helpless chicks. Parents of altricial species, such as pigeons, must work hard to provide a protein-rich diet to their chicks while they develop to the point of fledging. While altricial chicks are in the nest, the entire brood is at risk of predation. Their main protection is the hidden nest. Precocial chicks, by con- trast, are mobile and may avoid predation. It is less likely the entire brood will be lost to a predator. SMALL BRAINS AND BIG BRAINS The brains of altricial birds and precocial birds devel- op differently. The general pattern is that precocial chicks have larger brains than altricial chicks. But in adult birds the pattern is reversed: altricial adults have larger brains than precocial adults. Why? Precocial chicks have larger brains because their neural growth takes place in the egg, while in altricial species it occurs after hatching. The brains of preco- cial species are well-matured at hatching and will not grow much. The level of development at hatching must allow them to move independently and eat on their own. Altricial adults have larger brains because the continued development of many brain functions beyond hatching allows altricial species to achieve larger brain size. Ricklefs and Starck view altricial development as a mechanism to permit increased postnatal growth of the brain leading to large brain size in the adult. In other words, the biological purpose of altricial development may be to grow big brains. PIGEON BEHAVIOR By Mike McKaig PIGEON BABIES: BLIND BUT NOT BALD