Q.What are the features peculiar to Ratitae birds ? Give two examples.

Altricial young hatch helpless and dependent on parents; precocial young hatch already capable of independent movement and feeding.

Bird (and some other vertebrate) hatchlings are classified into two broad categories based on their state of development at hatching:

Altricial hatchlings

• Hatch in an immature, underdeveloped state.
• Typically blind (eyes closed), naked (no feathers/down) or very sparsely feathered, and largely immobile.
• Completely dependent on parents for warmth, protection and feeding for an extended period after hatching.
• Examples: pigeon, crow, sparrow, and most passerine (songbird) chicks.

Precocial hatchlings

• Hatch in a well-developed, mature state.
• Eyes open at hatching, body covered with down/feathers, and legs strong enough to stand and walk almost immediately.
• Able to leave the nest soon after hatching and can often feed themselves (or at least follow the parent to food) with much less parental dependence.
• Examples: domestic fowl (chicken) chicks, ducklings, and megapode chicks. …

Ducks (class Aves) show several peculiar adaptive characters suited to a semi-aquatic, swimming and filter-feeding life.

• Webbed feet: the toes are joined by skin webs, acting like paddles that make swimming efficient.
• Broad, flat bill: fitted with comb-like lamellae along the edges, used to filter small food particles (plants, small invertebrates) out of water and mud.
• Waterproof plumage: ducks have an oil (uropygial/preen) gland near the tail base; they spread this oily secretion over their feathers using their bill, which repels water and keeps the feathers from getting waterlogged, aiding buoyancy and insulation. …