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首页> 外文期刊>Ecological Applications >Combining demographic and count-based approaches to identify source-sink dynamics of a threatened seabird
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Combining demographic and count-based approaches to identify source-sink dynamics of a threatened seabird

机译：结合人口统计和基于计数的方法来识别受威胁海鸟的源汇动态

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Identifying source-sink dynamics is of fundamental importance for conservation but is often limited by an inability to determine how immigration and emigration influence population processes. We demonstrate two ways to assess the role,of immigration on population processes without directly observing individuals dispersing from one population to another and apply these methods to a population of Marbled Murrelets (Brachyramphus marmoratus) in California (USA). In the first method, the rate of immigration (i) is estimated by subtracting local recruitment (recruitment from within the population due to reproduction) estimated. with demographic data from total recruitment (f; recruitment from within the population plus recruitment from other populations) estimated using temporal symmetry mark-recapture models developed by R. Pradel. The second method compares population growth rates estimated with temporal symmetry models (lambda(TS)) and/or population growth rates estimated from counts of individuals over multiple sampling periods (lambda(C)) with growth estimates from a stage-structured projection matrix model (lambda(M)). Both lambda(TS) and lambda(C) incorporate all demographic processes affecting population change (birth, death, immigration, and emigration), whereas matrix models are usually constructed without incorporating immigration. Thus, if lambda(TS) and lambda(C) are >= 1 and lambda(M) < 1, the population is sustained by immigration and is considered to be a sink. Using the first method, recruitment estimated with temporal symmetry models was high (f = 0.182, SE = 0.058), the mean adult birth rate, as estimated using the ratio of juveniles to >= 1 year old individuals (observed during ship-based surveys) was low (bA = 0.039, SE = 0.014), and immigration was 0.160 (SE = 0.057). Using the second method, murrelet numbers in central California were stable (lambda(C) = 1.058, SE = 0.047; lambda(TS) = 1.064, SE = 0.033), but were projected to decline 9.5% annually in the absence of immigration (lambda(M) = 0.905, SE = 0.053). Our results suggest that Marbled Murrelets in central California represent a sink population that is stable but would decline. in the absence of immigration from larger populations to the north. However, the extent to which modeled immigration is due to permanent recruitment or temporarily dispersing individuals that simply mask population declines is uncertain.
机译：确定源汇动态对于保护至关重要，但常常因无法确定移民和移民如何影响人口进程而受到限制。我们展示了两种评估移民作用的方法，即不直接观察个人从一个人口散布到另一个人口的过程，而是将这些方法应用于美国加利福尼亚州的Marbled Murrelets（Brachyramphus marmoratus）人口。在第一种方法中，移民率（i）通过减去估计的本地招聘人数（由于繁殖而从人口内部招聘）来估算。使用R. Pradel开发的时间对称标记重获模型估算的总招募人口统计数据（f;从人群内部招募再加上其他人口招募）。第二种方法将使用时间对称模型（lambda（TS））估计的人口增长率和/或根据多个采样周期内的个体计数估计的人口增长率（lambda（C））与阶段结构投影矩阵模型的增长估计进行比较（lambda（M））。 lambda（TS）和lambda（C）都纳入了影响人口变化（出生，死亡，移民和移民）的所有人口统计过程，而矩阵模型通常是在没有移民的情况下构建的。因此，如果lambda（TS）和lambda（C）> = 1且lambda（M）<1，则该人口由移民维持，被认为是汇。使用第一种方法，使用时间对称模型估算的招聘人数较高（f = 0.182，SE = 0.058），即成年人的平均出生率，该比例是使用少年与> = 1岁个体的比率估算的（在基于船的调查中观察到） ）低（bA = 0.039，SE = 0.014），迁移为0.160（SE = 0.057）。使用第二种方法，加州中部的murrelet数量是稳定的（lambda（C）= 1.058，SE = 0.047; lambda（TS）= 1.064，SE = 0.033），但在没有移民的情况下，预计每年下降9.5％（ λ（M）= 0.905，SE = 0.053）。我们的研究结果表明，加利福尼亚中部的Marbled Murrelets代表着一个稳定的汇聚人口，但会下降。没有大量人口向北部移民。然而，模范移民的程度是由于永久性招募或暂时分散个人以掩盖人口下降的程度尚不确定。

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