Different kinds of development by vertebrates after birth The two kinds of developmental strategies for birds after birth, is mainly linked to nest building, feeding and protecting from predators in their environment. Altricial development (‘requiring nourishment’) Precocial development

Altricial development Altricial refers to species whose newly-hatched or -born youngs are helpless and require care for a specific amount of time. They … are relatively immobile, lack hair or feathers, are not able to obtain food on their own, must be cared for by adults, have closed eyes which are common, though not always the case. They cannot leave the nest and are fed by their parents until their body is covered in feathers and their muscles have strengthened. They are unable to regulate their own body temperature. (kept warm by a parent)

Altricial development (cont.) Their nest are above the ground in trees or on poles to protect them from predators. Amongst birds, for example,  woodpeckers, owls, pigeons, etc. Among mammals, most rodents (rat, mouse, marmot) are altricial.  Cats, dogs, humans are some of the best-known altricial organisms.

Advantage of altricial development With rich diet provided by parents the initial small brains developed into large adults brains – leads to greater adaptability and intelligence

Disadvantage of altricial development More demanding on parents (more energy needed) for protection and feeding Parents need to teach them to fly

Precocial development Precocial refers to species in which the young are relatively mature and mobile from the moment of birth or hatching. They … are able to move around soon after hatching, are covered with down /feathers, can leave the nest within two days, are able to regulate their own body temperature, Make their nests on the ground Examples: guinea fowl, geese, ducks, chickens, cranes, etc.

Advantage of precocial development Hatchings are able to avoid predation to some extent, They can see and run around, Can feed themselves, Less demanding on female/ parents once hatched – they are independent Mother stays nearby to protect them and teach them

Disadvantage of precocial development Hatchlings have relatively large brains and their brain size does not increase much Demanding on female to produce lots of yolk so that embryo can develop into more mature chicks

Increasing parental care

ALTRICIAL DEVELOPMENT PRECOCIAL DEVELOPMENT Some differences ALTRICIAL DEVELOPMENT PRECOCIAL DEVELOPMENT Woodpeckers, pigeons, guineafowel Chickens, duck, geese, owls 25% of yolk – less energy needed to produce 40% of yolk in egg – lots of energy needed to produce Nests in trees, caves, on poles Nests on the ground Closed eyes Open eyes Naked very few or no feathers Down/feathers present Cannot leave the nest Leave nest within two days Cannot move around Can move around Cannot feed themselves Can feed themselves Cannot maintain their body temperature (kept warm by a parent) Can maintain their body temperature Parents have to protect them from predators Parents may help to protect them Need a lot of parental care for amount of time Very little or no parental care