bluegreen-labs/apus_pallidus_foraging: Apus pallidus foraging study (2019 - 2020)

<strong>Non-breeding Pallid swifts favour the aeroecology of atmospheric convergence zones</strong> Trans-Saharan migratory bird species encounter large scale seasonal atmospheric convergence zones, where opposing monsoon and continental air masses meet. These macro-scale atmospheric conditions determine local weather, influence migratory and foraging behaviour and seasonal bird survival rates. Here we investigate the flight behaviour of Pallid swifts (<em>Apus pallidus</em>), a small aerial insectivore, in relation to non-breeding season atmospheric conditions using state-of-the-art GPS logged data. Our analysis suggests that pallid swift prey on insects by catching them where they are most densely concentrated within the atmosphere. Residence of birds in West Africa well past the vegetation minimum suggests that the state of the vegetation and associated local insect populations are not necessarily limiting. Migration events within, to and from, the non-breeding season foraging locations might therefore not only be guided by a decline in vegetation as common metric for prey availability, but also by shifting wind directions and their concentrating effects. <strong>Supporting materials</strong> This repository includes all data to reproduce the statistics in the described study, above. Certain omissions were made due to the data volumes involved. The latter mostly pertain to the visualization of the processes involved using transects through the atmosphere. <strong>Data structure</strong> Key data is saved in compressed R serial files (.rds) in the <code>data</code> folder. The <code>position_data.rds</code> file contains bird positions, headings and ancillary data to support most of the analysis in the study. Additional rds files are included which cover spatial analysis (ITF_location.rds, *_shear_index.rds, shear_index_fields.rds), as well as atmospheric analysis (temperature_profiles.rds). Data in the <code>data</code> folder are generated using raw data from the <code>data-raw</code> folder, and its included scripts. <strong>Code execution</strong> It is best to execute code in the numeric sequence as provided in the filename. Although it should not matter for the statistical analysis. <strong>Licensing</strong> Be mindful of the Open Database License (ODbL) which is a copyleft license. Reuse is permitted on the condition that any database in which this database is used remains open as well. The authors will enforce this policy.**《非繁殖期苍白雨燕偏好大气汇聚带的空中生态环境》** 跨撒哈拉迁徙鸟类会遭遇大规模季节性大气汇聚带（atmospheric convergence zones）——即季风气团与大陆气团交汇的区域。这类大尺度大气条件不仅决定局地天气，还会影响鸟类的迁徙与觅食行为，以及季节性存活率。本研究借助最先进的GPS定位数据（GPS logged data），探讨了非繁殖期内，小型空中食虫鸟类苍白雨燕（*Apus pallidus*）的飞行行为与大气条件的关联。分析结果表明，苍白雨燕会通过捕食大气中密度最高的昆虫种群来获取食物。研究发现，鸟类在西非的停留时间远超植被量最低的时段，这说明植被状态及其关联的当地昆虫种群未必是限制因素。因此，非繁殖期觅食地内、往返觅食地的迁徙行为，其引导因素或许不只是作为猎物可获得性通用指标的植被减少，还包括风向变化及其带来的汇聚效应。 **支撑材料** 本数据集仓库包含复现上述研究中所有统计结果所需的全部数据。由于数据量较大，部分内容未被收录，其中主要涉及利用大气断面可视化相关过程的材料。 **数据结构** 核心数据以压缩的R序列化文件（后缀为.rds）存储于`data`文件夹中。其中`position_data.rds`文件包含鸟类位置、飞行航向及辅助数据，可支撑本研究中绝大多数分析内容。此外还包含其他rds文件，分别用于空间分析（`ITF_location.rds`、`*_shear_index.rds`、`shear_index_fields.rds`）以及大气分析（`temperature_profiles.rds`）。`data`文件夹中的数据由`data-raw`文件夹中的原始数据及配套脚本生成。 **代码运行** 建议按照文件名的数字顺序执行代码，尽管这对统计分析而言并非必需。 **授权协议** 请注意本数据集采用开放数据库许可协议（Open Database License, ODbL），这是一种著佐权（copyleft）许可协议。允许二次使用的前提是，使用该数据库的任何衍生数据库同样需保持开源。作者将严格执行该许可政策。