Attendance at a Sage Grouse Lek: Implications for Spring Censuses

Abstract

Numbers of adult male sage grouse (Centrocercus urophasianus) increased between early March and late April-early May. Yearling cocks began attending in numbers when female numbers peaked in early April. Hens stayed for shorter daily and seasonal periods than cocks did. Data on seasonal and daily attendance confirm the validity of the Patterson census technique, but suggest that it is more restrictive than necessary. Peak numbers of cocks can be estimated to within 90 percent by the highest of 3 counts between 1/ hour before and 11/2 hours after sunrise during the first 3 or the second and third weeks after the peak of breeding. J. WILDL. MANAGE. 42(1):46-52 The daily activities of sage grouse during the period of the lek have not been carefully documented (Johnsgard 1973:165). Biologists census sage grouse in the early dawn hours during the mating season and are well aware of the general pattern of predawn arrival of cocks on the arena and their departure soon after sunrise. Although the basic spring census technique takes daily activity of the grouse into account, precise data on lek arrival and departure times throughout the breeding season are not available. From 1969 to 1971 we conducted a detailed study of male sage grouse on a lek in central Montana (Hartzler 1972). In order to interpret the significance of male behavior, we also studied the arrival and departure times of the birds during both morning and evening lek periods throughout each season. This is an important aspect of sage grouse biology, and also provides the basis for the proper timing (both daily and seasonal) of spring censuses. These data allow us to test statistically the validity of the widely used Patterson census techniques (Patterson 1952). The term arena is restricted to the place where the grouse display while the term lek refers to birds gathered on the arena, or to the birds and the arena collectively (Koivisto 1965).