The management of avian populations at risk requires accurate estimates of vital rates across age and sex classes to effectively identify the most vulnerable demographic and support conservation actions. In the endangered Red Knot (Calidris canutus rufa), there are relatively few reliable estimates of reproductive success because they breed in such low densities across such a large and relatively inaccessible area in Arctic Canada. The purpose of this study is to test whether a migratory time lag between adult male and female knots during post-breeding southbound migration could be a reliable index of reproductive success for this species. If so, we expected to find a positive relationship between a time lag in male migration and the number or proportion of juveniles present at the same fall migration site. To test this hypothesis, we analyzed 13 years of capture-mark-recapture and census data from an important staging area during southbound migration. We found a strong and consistent age and sex-specific chronology; median passage dates for females were approximately 2 weeks earlier than males, with juveniles following 1 month later than adults of both sexes. For most years, there was a significant time lag of up to 27 days between females and males. However, we found no evidence to support that this time lag explained variation in the number of juveniles at the stopover site each year. Instead, we found that the timing of female migration along with an index of environmental conditions on the breeding grounds and during migration best described the proportion of juveniles present during migration. Overall, our results cast doubt on the reliability of the male migratory time lag as an indicator of breeding success.

中文翻译：

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雌性迁徙物候和气候条件解释了秋季迁徙期间的幼年红结 (Calidris canutus rufa) 数量

管理处于危险中的禽类种群需要准确估计不同年龄和性别类别的生命率，以有效识别最脆弱的人口并支持保护行动。在濒临灭绝的红结（Calidris canutus rufa）中，繁殖成功的可靠估计相对较少，因为它们在加拿大北极地区如此大且相对难以进入的地区以如此低的密度繁殖。本研究的目的是测试在繁殖后南行迁移期间成年雄性和雌性结之间的迁移时间滞后是否可以作为该物种繁殖成功的可靠指标。如果是这样，我们预计会发现男性迁徙的时间滞后与同一秋季迁徙地点的青少年数量或比例之间存在正相关关系。为了检验这个假设，我们分析了南行迁移期间一个重要集结地的 13 年捕获-标记-重新捕获和人口普查数据。我们发现了一个强有力且一致的年龄和性别特定年表；雌性的中位通过日期比雄性早大约 2 周，而青少年则比成年男女晚 1 个月。在大多数年份，女性和男性之间存在长达 27 天的显着时间差。然而，我们没有发现任何证据支持这一时间滞后解释了每年中途停留地点青少年数量的变化。相反，我们发现雌性迁徙的时间以及繁殖地和迁徙期间的环境条件指数最好地描述了迁徙过程中幼体的比例。全面的，