We have that \(\sin ^{2} \theta+\sin \theta=1\). Subtracting \(\sin ^{2} \theta\) from both sides and rearranging gives \(\sin \theta=1-\sin ^{2} \theta=\cos ^{2} \theta\). Then \(\cos ^{4} \theta+\cos ^{2} \theta=\cos ^{2} \theta\left(\cos ^{2} \theta+1\right)=\sin \theta(\sin \theta+1)=\sin ^{2} \theta+\sin \theta=1\).
Final Answer: The final answer is 1 .