Describe how the development of a special beak shape could affect a bird species’ survival.

The different beak shapes allow the birds to eat different things. I'd look at Darwin's finches for a better example. 

The truman doctrine was an american foreign policy whose stated purpose was to counter soviet geopolitical expansion during the cold war. it was announced to congress by president harry s. truman on march 12, 1947, and further developed on july 12, 1948, when he pledged to contain threats to greece and turkey