ABSTRACT Intervening when bird nestlings are performing poorly relative to the population mean may be a management priority if individuals are of high-conservation value. Assessing body condition may enable identification of potential problems before they cause mortality. We aimed to provide a tool for conservation managers to identify underperforming nestlings in a severely threatened bird population. We develop models of nestling growth and empirically quantify nestling body condition of critically endangered Orange-bellied Parrots Neophema chrysogaster, which have declined to only a single population in southwestern Tasmania, Australia. Using census data on growth of nestlings born over four years into the contemporary wild population, we test whether a body condition index is influenced by sex, hatch order, year of birth, brood size, whether one or both parents were captive bred, and fledging date. The best model describing body condition in Orange-bellied Parrot nestlings included additive effects of year of birth and hatch order. Nestling body condition was lowest in 2013, where first hatched nestlings were 2.5 g lighter than those born in 2016, and > 4.2 g lighter than in 2017/18. Nestlings that hatched either first or in the middle of the brood were respectively 4.8 g and 3.8 g heavier than last-hatched birds. Our body condition index provides a repeatable, rapid and cheap way to assess body condition of wild Orange-bellied Parrot nestlings. This represents a step towards accurate evaluation of management actions aimed at improving reproductive outcomes for this species, and provides a framework for developing hypotheses to test using an empirical and measurable index of individual quality.

中文翻译：

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极度濒危橙腹鹦鹉Neophema chrysogaster的雏鸟生长和体况

摘要 如果个体具有高保护价值，则在雏鸟相对于种群平均值表现不佳时进行干预可能是管理的优先事项。评估身体状况可以在潜在问题导致死亡之前对其进行识别。我们旨在为保护管理人员提供一种工具，以识别受到严重威胁的鸟类种群中表现不佳的雏鸟。我们开发了雏鸟生长模型，并根据经验量化了极度濒危的橙腹鹦鹉 Neophema chrysogaster 的雏鸟身体状况，它们在澳大利亚塔斯马尼亚州西南部已经下降到只有一个种群。使用在当代野生种群中出生超过四年的雏鸟生长的普查数据，我们测试身体状况指数是否受性别、孵化顺序、出生年份、育雏大小、父母一方或双方是否是圈养繁殖的，以及羽翼未丰的日期。描述橙腹鹦鹉雏鸟身体状况的最佳模型包括出生年份和孵化顺序的累加效应。雏鸟体况在 2013 年最低，首次孵化的雏鸟比 2016 年出生的雏鸟轻 2.5 克，比 2017/18 年轻 4.2 克。先孵化或在孵化中间孵化的雏鸟分别比最后孵化的鸟重 4.8 克和 3.8 克。我们的身体状况指数提供了一种可重复、快速且廉价的方法来评估野生橙腹鹦鹉雏鸟的身体状况。这是朝着准确评估旨在改善该物种繁殖结果的管理行动迈出的一步，