Data from: 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 range area. Finally, I reinforce the view that the island
syndrome is a general pattern in birds, spanning diverse phylogenetic and
ecological groups, by showing that in a seabird-only dataset (242
species), breeding island endemic seabirds show evolution of smaller
clutch sizes. In a model of the full dataset of both landbirds and
seabirds (4,530 species) there was no evidence of an interaction of being
a seabird with breeding island endemicity, showing that seabirds and
landbirds respond in the same way. This study, using more than 40% of all
bird species, provides the first evidence of a general evolutionary
response in a life history trait, clearly showing the island syndrome as a
general evolutionary tendency associated with island environments.

"岛屿综合征（island syndrome）"指岛屿生物在生物学特征上的相似性，但其普遍性存疑，因为所研究的物种范围与性状往往有限。本文利用涵盖4530种鸟类的数据集，揭示仅在岛屿繁殖的鸟类（繁殖岛屿特有种，breeding island endemics）演化出更小的窝卵数。

通过采用繁殖岛屿特有种的包容性定义（涵盖迁徙物种与海鸟），我运用系统发育广义线性模型（phylogenetic generalized linear models）分析了岛屿繁殖鸟类窝卵数（clutch size）的演化规律。

在不同的系统发育假说下，且控制生物与地理协变量后，结果显示繁殖岛屿特有陆鸟（470种）的窝卵数显著小于大陆繁殖鸟类（3818种）。

此外，繁殖岛屿特有陆鸟的窝卵数与其繁殖范围面积呈正相关，这表明窝卵数的演化符合岛屿综合征的预期。

最后，通过仅包含海鸟的数据集（242种）分析发现，繁殖岛屿特有海鸟同样演化出更小的窝卵数，这进一步支持了岛屿综合征是鸟类中跨多样系统发育与生态类群的普遍模式这一观点。

在包含陆鸟与海鸟的完整数据集（4530种）模型中，未发现海鸟身份与繁殖岛屿特有性之间存在交互作用，说明海鸟与陆鸟的响应模式一致。本研究覆盖了超过40%的鸟类物种，首次为生活史性状的普遍演化响应提供了证据，明确表明岛屿综合征是与岛屿环境相关的普遍演化趋势。