If these are all single objects (as opposed to a pattern used to fill an area) the simplest way would be to put your penguin on a separate layer above the stitches and then lock the layer (using the little lock icon next to the eye in your layers palette).
Then, using your penguin form as a guide, simply select and delete the stitches at the edge which need deleting. Some which are mostly outside the penguin you'll probably delete while some which are only minimally outside you'll probably keep.
I think that's the best way to go at it, because you'll have to visually choose which stitches to keep or delete depending on how it affects the whole.
Then the rest of the stitches well outside can all be selected in large amounts by click and dragging over them to select them.
(If the stitches are all grouped then ungroup them by Ctrl+Shift+G, or alternatively use the white arrow tool to select them).