The first warm-blooded vertebrates are:

Which of the following is a characteristic feature of $Aves$?

The presence of feathers and the power of flight are characteristic features of:

$A$: All birds,except the one like Koel (cuckoo),build nests for retiring and taking rest during night time.
$R$: Koel lays eggs in the nests of tailor bird.

What type of fertilization occurs in birds?

The feet of a kingfisher are adapted for ...............