ACCorDing to thE pAssAgE, whiCh oF thE Following DEtErminEs thE shApE AnD Coloring oF thE plumAgE oF A givEn spECiEs oF BirD within A givEn ECologiCAl niChE
A．thE EmErgEnCE oF A CompEting spECiEs who rEly upon thE sAmE FooD sourCE As thE First spECiEs
B．thE physiCAl AppEArAnCE oF thE FooD supply AvAilABlE in thE niChE to thE givEn spECiEs
C．thE ABility oF thE First spECiEs to CollECt AnD mAkE usE oF thE nutritionAl propErtiEs oF thE FooD within in thE niChE
D．thE physiCAl AppEArAnCE oF rivAl mAlEs within thE spECiEs who CompEtE For Both thE sAmE FooD supply AnD FEmAlEs
E．(E) thE physiologiCAl EFFECts on FErtility oF thE FooD AvAilABlE in thE niChE