Maximum of the function F(X)=X*(1+X)^0.5

Hello,
Is x=-1 local maximum of $F(x)=x\sqrt{1+x}$
On the one hand, $F(-1+\delta)<F(-1)$ for $0<\delta<1$.
However, $F(-1-\delta)$ is not defined.
As far a I know, the point x=a is considered local maximum, if there exists small neighborhood $\delta$ such that $F(a)>F(x)$ for every $a-\delta<x<a+\delta$.

So is x=-1 a local maximum or not?