EPHEMERAL LEKKING BEHAVIOR IN THE BUFF-BREASTED SANDPIPER, TRYNGITES SUBRUFICOLLIS

We studied male reproductive behavior of the buff-breasted sandpiper T ryngites subruficollis for three years on a 16-km(2) study site in nor thern Alaska to document variation in male lekking behavior and to exp lore the causes of that variation. During the breeding season, about 7 5% of males on the study area displayed on leks, with the remainder di splaying solitarily. Leks averaged between 2.3 and 3.0 males each (max imum size = 20). Most leks (69%) were present in only one year and abo ut one-tenth were active all three years. Half of the leks were active for only one survey (maximum of 3-4 days) in a given year. Individual male behavior varied substantially, from remaining at a single lek fo r most of the breeding season or attending multiple leks during the se ason, to displaying solitarily or displaying both on leks and solitari ly Some males (30% or fewer) displayed near nests during the later par t of the breeding season, perhaps attempting to copulate with females during egg-laying. The proportion of males that displayed on leks rema ined consistently high throughout the breeding season despite changes in the operational sex ratio and in the intensity of male-male competi tion. However, the absolute number of males (lekking and solitary) in the study area was positively correlated with the number of fertile fe males during both breeding seasons. We suggest that buff-breasted sand pipers may be unusual among lek-breeding birds in that males have the option of leaving areas when the number of fertile females becomes dep ressed and flying to new areas where breeding opportunities are still available. Breeding opportunities may be especially variable in the hi gh arctic because of uneven snow accumulation and differential melt-of f that can delay breeding by two or more weeks. This interpretation su ggests that the mating system of the buff-breasted sandpiper must be v iewed at a much larger scale than what has typically been used in mati ng system studies.