Nest site choice and construction by ground-nesting shorebirds can have important repercussions for survival and reproductive success, potentially impacting predation risk, mate retention and hatching success. One such decision, lining nests with shell fragments, was investigated in the Piping Plover (Charadrius melodus). Data were collected describing the placement, construction and fate of 34 nests on Cape Cod, Massachusetts, USA in 2003. Model selection criteria were used to determine the habitat variables that most strongly influence nest lining. The best model included variables related to both the immediate surrounding (proportion of the substrate made up of shell and rock, and sand granularity), as well as nest location (distance from the dune). Plovers used more shell fragments in nests that are on shelly, rocky, or coarse-sanded beaches, and when nesting closer to dunes. There was a negative correlation between fledging success and the amount of shell surrounding the nest. These results and related conservation implications are explored for this threatened shorebird.