Bird health can significantly affect spring reproductive fitness. A better understanding of how female sage grouse health varies with seasonal nutrition changes provides insight for determining if specific nutritional habitats are limiting bird productivity. In 2004, greater sage grouse adult and yearling hens were captured, and blood samples collected, during breeding (MARCH: March 15 to April 11; n = 22), early brood rearing (MAY: May 20 to June 22; n = 21), and on summer range (JULY: July 7 to August 17; n = 19) in two distinct but similar northern Nevada population management units (Tuscarora [TU] and Lone Willow [LW]). In TU, yearlings weighed less (P < 0.043) than adults at all sampling periods. No age-related differences were observed for LW birds. Serum blood chemistry values were influenced by site, bird age, and season. Adults had more plasma protein and albumin than yearlings during MARCH (P < 0.005) followed by a decrease by MAY (P < or = 0.0001). Lone Willow females had higher albumin levels (P = 0.0005). Higher serum phosphorus levels were detected for LW females during MARCH (P < 0.0001), and no site differences were detected for MAY or JULY. Tuscarora yearlings had lower serum calcium levels than adults during MARCH (P < 0.0001); LW yearlings had lower levels than adults during MAY (P = 0.030). Both TU yearlings (MARCH P < 0.0001) and adults (MARCH P < 0.0001; MAY P = 0.040) had lower values than LW counterparts. Tuscarora adults and LW yearlings and adults showed decreases between MARCH and MAY (P < 0.0001). The combination of lower yearling weight, plasma protein, and serum calcium and phosphorus in the TU birds indicates a lower nesting and re-nesting potential. Leading to the conclusion that TU yearlings contributed less to the population production than LW yearlings for that particular year.