Birds that breed exclusively on islands have smaller clutches

The ‘island syndrome’ refers to similarity in the biology of island organisms, but its generality is questionable, as the scope of species and traits examined are often limited. Here, I show that birds breeding exclusively on islands (breeding island endemics) evolved smaller clutches, using a dataset of 4,530 bird species. Using an inclusive definition of a breeding island endemic, which also encompasses migratory species and seabirds, I examine the evolution of clutch sizes in island breeding species using phylogenetic generalized linear models. Across disparate phylogenetic hypotheses, and after accounting for biological and geographical co-variables, I show that breeding island endemic landbirds (470 species) evolved smaller clutch sizes than continental breeding species (3,818 species). I show that the evolution of clutch size follows the expectations of the island syndrome, as among breeding island endemic landbirds there is a positive relationship between clutch size and breeding..., , , # Data from: Birds that breed exclusively on islands have smaller clutches

Related article published in *Ornithology* in 2024 by M. T. Jezierski.

Data and code versioned 16th January 2024. README versioned 16th January 2025.
[[e-mail]](mailto:[e-mail])

[https://github.com/jezierskim/clutch](https://github.com/jezierskim/clutch)

## Repository contents:

#### README file (this).

* clutch_data_code.R (R script for data preparation; uses files: clutch_dataset.csv and dev_sp.csv)
* clutch_dataset.csv (raw data for the above R script)
* dev_sp.csv (family level data on precociality)
* analysis_dataset.csv (final output of clutchdatacode.R; to be used with clutch_analysis_code.R)
* clutch_analysis_code.R (R script for data analysis; uses the file seabirds.csv)
* seabirds.csv (list of species identified as seabirds (see Methods))

#### In addition to files provided in the repository, clutch\_data\_code.R requires two extra files that cannot be provided due to ...

# 数据集说明
“岛屿综合征（island syndrome）”指岛屿生物在生物学特征上呈现出的趋同性，但其普适性尚存争议，因现有研究往往受限于所考察的物种类群与性状范围。本研究基于涵盖4530种鸟类的数据集，证实仅在岛屿上繁殖的鸟类（岛屿繁殖特有种，breeding island endemics）演化出了更小的窝卵数（clutch）。

本研究采用涵盖迁徙物种与海鸟的广义岛屿繁殖特有种定义，通过系统发育广义线性模型（phylogenetic generalized linear models）分析岛屿繁殖物种的窝卵数演化规律。在不同的系统发育假说框架下，且在控制了生物学与地理协变量之后，本研究证实：岛屿繁殖特有陆鸟（共470种）的窝卵数小于大陆繁殖鸟类（共3818种）。本研究还发现，窝卵数的演化符合岛屿综合征的预期——在岛屿繁殖特有陆鸟类群中，窝卵数与繁殖……呈正相关关系。

# 数据来源：仅在岛屿繁殖的鸟类窝卵数更小

相关研究论文于2024年发表于《Ornithology》（《鸟类学》），作者为M. T. Jezierski。

数据与代码版本更新于2024年1月16日；README文档版本更新于2025年1月16日。
邮箱：[e-mail]
项目仓库：https://github.com/jezierskim/clutch

## 仓库内容
#### README文档（即本文档）
* clutch_data_code.R：用于数据预处理的R脚本，依赖文件为clutch_dataset.csv与dev_sp.csv
* clutch_dataset.csv：上述R脚本所用的原始数据
* dev_sp.csv：关于早成鸟的科级水平数据
* analysis_dataset.csv：clutchdatacode.R的最终输出结果，需配合clutch_analysis_code.R使用
* clutch_analysis_code.R：用于数据分析的R脚本，依赖文件为seabirds.csv
* seabirds.csv：被鉴定为海鸟的物种种列表（详见研究方法）

除本仓库提供的文件外，clutch_data_code.R还依赖两个因原文未说明原因无法提供的额外文件。