Give scientific reasons: Birds can fly for long distances continuously.

(N/A) $1$. The flight muscles of birds are composed of red muscle fibers.
$2$. These fibers contain a high concentration of myoglobin,which acts as an oxygen-storing pigment.
$3$. Red muscles are rich in mitochondria,which facilitate aerobic respiration to produce large amounts of $ATP$.
$4$. Due to the efficient aerobic metabolism and high $ATP$ production,these muscles do not get fatigued easily,allowing birds to fly continuously for long distances.