First of all draw a beak and the top part of the head (it to be at an angle and it is similar to a hat form), a big eye with a patch of light and part of a neck.
Draw a trunk of a martin.
Further the tail, it is similar on Lastochkin, and the put wing, quite long.
Then we draw the second wing and a paw.
Draw feathers at a bird.
Put dark and light sites of plumage at a martin, using for more dark tones — pencils of bigger softness (4,6, 9V), for light — firmer from N to 2B. Also for patches of light and for correction of color use an eraser.