While Kino's environment is safe and pleasant, how does the picture of the ants and the roosters underscore the struggle for the survival in nature...

The struggle of the animals and insects is both foreshadowing and a metaphor for Kino’s existence.

Steinbeck describes the setting very carefully.  When Kino wakes up, we learn about the world around him as Kino observes it.  Although Kino seems content, with his wife and child by his side, there is something lurking below the surface.  The yard battles are a metaphor for the struggle of Kino’s everyday life, and they foreshadow trouble to come.

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The struggle of the animals and insects is both foreshadowing and a metaphor for Kino’s existence.

Steinbeck describes the setting very carefully.  When Kino wakes up, we learn about the world around him as Kino observes it.  Although Kino seems content, with his wife and child by his side, there is something lurking below the surface.  The yard battles are a metaphor for the struggle of Kino’s everyday life, and they foreshadow trouble to come.

The ants were busy on the ground, big black ones with shiny bodies, and little dusty quick ants. Kino watched with the detachment of God while a dusty ant frantically tried to escape the sand trap an ant lion had dug for him. (Ch. 1)

Kino’s reaction to the ants is similar to the reaction the colonists like the doctor and the pearl sellers have toward him.  Kino is on top of the food chain here, and he can watch with godlike detachment.  It matters not to him what the ants go through.  However, in terms of people he is at the bottom.  He is just as insignificant as an ant to the doctor and pearl sellers.

The roosters posturing and the doves flying overhead are also symbolic.

Near the brush fence two roosters bowed and feinted at each other with squared wings and neck feathers ruffed out. It would be a clumsy fight. They were not game chickens. Kino watched them for a moment, and then his eyes went up to a flight of wild doves twinkling inland to the hills. (Ch. 1)

Like the roosters, Kino has to make himself more important than others to win.  He is not very good at fighting against the system, however.  Kino’s temper always gets the best of him, and he does not think or act rationally.

While things are simple and peaceful in this little domestic scene, there is plenty of hostility just under the surface.  Kino may be living a simple life now, but things are about to get much more complicated and dangerous for him and his family.