Minimax decision function about poisson

Question

Let $X_1,...,X_n$ be independent r.v.'s from the poisson $P(\theta)$ ,$\theta \in (0,\infty)$.

and consider loss function $L(\theta ; \delta ) =\frac{[\theta - \delta(x_1,...,x_n)]^2}{\theta}$.

then risk $R(\theta ; T ) =1/n$ where $T=\frac{X_1+...+X_n}{n}$.

Then $T$ is minimax?

If there is distribution $\lambda$ on $(0,\infty)$ such that $T$ is bayes rule for $\lambda$, then $T$ is minimax because $R(\theta ; T)$.

Could you help me?