I used some painted strips of linen for the grass. I pulled out some threads from each strip, so they looked a little grassy.
For the tree I couched down some wool yarns. I wasn't quite sure the best way to do the branches, but I ended up unraveling the yarn at the ends. They are a little loose at the ends, since it was impossible to stitch down where they thinned down.
For the leaves I cut up bits of a specialty yarn and just sewed them down irregularly.
You can see the details in the closeup photo:
|Sparrow with nest material|