Remember that it can be very helpful to change the dropdown scope menu from the default "Collins, Summit, & Articles, etc" to just "Collins" when searching for books. 

When searching for books, try different variations on your topic. For instance, you could try searching for 'Olympic mountain goat relocation' but you could also try "species reintroduction" or "wildlife translocation" to find books on the broader topic that aren't focused as narrowly on this one example.