SURVIVAL AND CAUSE-SPECIFIC MORTALITY OF FEMALE NORTHERN PINTAILS IN SOUTHERN SASKATCHEWAN

Abstract

Unlike most prairie-nesting ducks, the North American population of northern pintails (Anas acuta) has shown limited response to improved wetland conditions on the U.S. and Canadian prairies during the mid to late 1990s. Because adult female survival is a key parameter affecting waterfowl population dynamics, and a large fraction of annual mortality for some dabbling ducks occurs during the nesting season, we used radiotelemetry to estimate nesting season survival and cause-specific mortality of adult female northern pintails that were monitored during an induced renesting study. We conducted our research in a predominantly agricultural landscape in southern Saskatchewan during 1998–2000, an area that is typical of much of the pintail's prairie breeding range. The survival rate of 140 females for a 75-day interval (30 Apr–14 Jul) during the nesting season was 0.806 ± 0.046. Survival did not vary among years or between ages (second-year, after second-year), nor was it related to female body condition (body mass adjusted for structural size, date, and year of capture). We documented 15 mortalities and found that the 75-day mortality rate due to raptors (0.141 ± 0.040) was greater than that due to red fox (Vulpes vulpes; 0.011 ± 0.011), collisions with power lines (0.011 ± 0.011), or unknown factors (0.039 ± 0.027). Our results differ from prior research that indicated red fox was a major predator of female pintails during the nesting season. Raptors were the primary mortality agent for female pintails, perhaps because of limited exposure during incubation in our study, or the use of open habitats by pintails in southern Saskatchewan. Management programs that provide nesting or wetland habitats with overhead concealment, or that reduce perch sites for raptors in areas with high pintail densities, may decrease the risk of avian predation on female pintails.