Waterfowl nest searches are labor intensive and expensive. Development of a method to estimate number of nests without conducting nest searches would be advantageous. Mottled duck (Anas fulvigula maculosa) chase flights were compared with number of nest initiations to determine if a quantifiable relationship exists. Frequency of chase flights over an area was independent of the number of nests found in the area (P > 0.10), precluding use of chase flight frequency to estimate nest density. Chase flight frequency does provide an index of breeding chronology. A highly significant relationship (P < 0.0001) between chase flights and total flights provides an index to mottled duck density that may be used to identify changes in population size and evaluate changes in habitat use.