source_sink_vital_rates_Jun2024

<br>We use 26 years of data on reproduction, movement, and survival to estimate annual source-sink dynamics of the Everglade snail kite (<i>Rostrhamus sociabilis plumbeus</i>), an endangered wetland-dependent raptor in the United States. The biological invasion of a non-native apple snail <i>(Pomacea maculata</i>) provides a supplementary food source for snail kites and the increased prey availability has been linked to increases in reproduction, survival, body mass, and population growth. This analysis estimates fecundity, survival, and movement parameters as a function of years since invasion and how source-sink dynamics changed over time.The Everglade snail kite forms a spatially structured population limited to flooded freshwater wetlands and shallow lakes in peninsular Florida in the United States. Our study area includes all known breeding areas for the Everglade snail kite. Wetlands were grouped into 6 populations based on geographic location and hydrology: Paynes Prairie, Kissimmee River Valley, Okeechobee, Everglades, East, and St. John’s Marsh.For each vital rate (demographic parameter) we included linear, quadratic, and logarithmic effects of years since <i>P. maculata </i>invasion. We tested for interactive effects between years since invasion and snail kite age because the invasion may have affected younger birds differently. Here, the top models for each demographic rate are presented, please see (Beatty <i>et al.</i> for the full model list).To compare pre- and post-invasion estimates, a pre-invasion value was estimated for each vital rate using data before each population was invaded. Pre-invasion values were estimated separately to be able to estimate the distinct relationship between vital rates and time since invasion and because we expected patterns in vital rates to be different before the invasion. Pre-invasion estimates are a single value for each population and therefore do not vary with years since invasion. The Paynes Prairie population did not have snail kites breeding in it until after it was invaded and therefore pre-invasion data is missing for this site and years since invasion represents the number of years since snail kites began breeding in the invaded site.

本研究利用26年的繁殖、移动与存活数据，估算美国濒危湿地依赖型猛禽大沼泽地蜗牛鸢（Everglade snail kite，学名*Rostrhamus sociabilis plumbeus*）的年度源汇动态（source-sink dynamics）。斑苹果螺（Pomacea maculata）的生物入侵为蜗牛鸢提供了补充食物来源，猎物可获得性的提升与繁殖率、存活率、体质量及种群增长的提升存在显著关联。本分析以入侵后的年限为自变量，估算繁殖力、存活率与移动参数，并解析源汇动态随时间的变化规律。
大沼泽地蜗牛鸢形成空间结构化种群，仅分布于美国佛罗里达半岛的淹水淡水湿地与浅湖之中。本研究区域涵盖该物种所有已知的繁殖栖息地。研究人员依据地理位置与水文特征，将研究湿地划分为6个种群：佩恩斯草原、基西米河谷、奥基乔比、大沼泽地、东部种群与圣约翰沼泽。
针对每个生命率（vital rate，种群统计参数），我们纳入了斑苹果螺入侵后的年限的线性、二次与对数效应。我们检验了入侵年限与蜗牛鸢年龄间的交互效应，因为入侵可能对幼鸟产生差异化影响。本文仅展示各生命率的最优模型，完整模型列表详见Beatty等人的研究成果。
为对比入侵前后的估算结果，我们利用各种群被入侵前的观测数据，为每个生命率估算了入侵前的数值。单独估算入侵前数值的原因有二：一是可独立解析生命率与入侵后年限间的特异性关联；二是我们预期入侵前后的生命率变化模式存在显著差异。入侵前估算值为每个种群的单一固定值，因此不会随入侵后的年限发生变化。
佩恩斯草原种群直至该区域被入侵后，才出现蜗牛鸢的繁殖活动，因此该站点缺失入侵前的观测数据，此处的入侵后年限指代蜗牛鸢开始在该入侵区域繁殖后的时长。