  Let $\mathcal{H}$ be a hereditary abelian category over a field $k$ with
finite dimensional $\operatorname{Hom}$ and $\operatorname{Ext}$ spaces. It is
proved that the bounded derived category $\mathcal{D}^b(\mathcal{H})$ has a
silting object iff $\mathcal{H}$ has a tilting object iff
$\mathcal{D}^b(\mathcal{H})$ has a simple-minded collection with acyclic
$\operatorname{Ext}$-quiver. Along the way, we obtain a new proof for the fact
that every presilting object of $\mathcal{D}^b(\mathcal{H})$ is a partial
silting object. We also consider the question of complements for
pre-simple-minded collections. In contrast to presilting objects, a
pre-simple-minded collection $\mathcal{R}$ of $\mathcal{D}^b(\mathcal{H})$ can
be completed into a simple-minded collection iff the
$\operatorname{Ext}$-quiver of $\mathcal{R}$ is acyclic.
