The Reproductive Cycle of the Chukar

Abstract

This is a 2-year study (1958-60) of the reproductive cycle of the chukar (Alectoris graeca) in southeastern Washington. Pairing occurred from early February to late March, with birds over 1 year of age being the first to form pairs. The pair bond appeared to endure until early in the incubation period. Testicular recrudescence began during late January, progressing at a relatively gradual and constant rate; the full breeding condition appeared to be reached by late March and persisted about 3 months; and regression was two-phased, occurring largely within 4 to 6 weeks. Ovarian and oviducal cycles were timed similarly. Recrudescence began about February 1 and progressed in two phases, a period of gradual change followed by a period of rapid development before the onset of egg laying. Most females laid the first egg between mid-March and mid-April. Six captive females laid 221 eggs at a mean rate of 1.3 days per egg. Renesting persisted following loss of eggs prior to hatching; some females continued to lay until mid-July. Dates for initiation of incubation ranged from about April 19 to July 19, hatching from about May 1 to mid-August (peak about June 21). Regression of ovaries and oviducts occurred in two stages, a short period of extremely rapid change during incubation followed by a long period of gradual change. The present study provides a more detailed understanding of the reproductive cycle of the chukar than has been available previously and serves as a basis for future ecological and physiological investigations. Relatively few data are available on the reproductive cycle of the chukar. Galbreath and Moreland (1953) in Washington, Christensen (1954) in Nevada, and Harper et al. (1958) in California report primarily on releases, successful establishment, ecology, and general life history. Reproductive behavior is discussed only in general in these papers. This investigation was supported in part by funds provided for biological and medical research by the State of Washington Initiative Measure No. 171. The Washington Department of Game provided a collecting permit and funds to conduct studies during the summer of 1959. We wish to thank Dr. Irven O. Buss for his helpful suggestions, Dr. Richard A. Parker for assistance with statistical analyses, and Dr. Robert L. Eng for his comments concerning the manuscript. STUDY AREA The investigation was conducted on a 47-square-mile study area located adjacent to the Snake River in Whitman County, Washington. The steep, rocky, and deeply cut breaks of the Snake River Canyon characterize the area. A vertical drop of about 1,900 feet extends over an average distance of 2 miles from rolling farmlands adjacent to the upper margin of the Canyon to the Snake River. The slopes are covered by sagebrush-grassland type vegetation heavily interspersed by basalt outcroppings and talus slides. Daubenmire (1942) describes the vegetation of the area as within the Agropyron spicatumrr-Poa secunda vegetation zone. However, prevailing cover types vary as a result of edaphic and disturbance factors. The area is semiarid, receiving about 13 inches of precipitation annually. The chukar population on the study area resulted from releases of 700 game-farm birds stocked in several groups along the Snake River in Whitman County, Washington, during March and April, 1951 (Galbreath and Moreland 1953). The research