Although animals are born with a protective immune system, even the innate immune system is under development from birth to adulthood and this development may be affected by sex and growth. However, most knowledge comes from captive animals or long-lived slow growing species. Moreover, little is known about how innate immune function, the important first line of defence, develops during early life in fast-growing animals such as free-living passerines. We studied development of innate baseline immune function in nestlings of free-living jackdaws Corvus monedula. We measured four immune parameters (hemolysis, hemagglutination, bacterial-killing capacity, haptoglobin concentration) and structural body size (body mass, wing length, tarsus length) at day 12 and day 29 post-hatching. We found that three out of four immune parameters (hemolysis, hemagglutination, bacterial-killing capacity) substantially increased with nestling age and had roughly reached adult levels shortly prior to fledging. We found little differences in immune development between males and females despite them differing in structural development. We also found no evidence that the nestlings traded off immune development with growth. That nestlings rapidly increase innate baseline immune function during early life and similarly in males and females indicates the importance of a well-functioning immune system already during the nestling phase.

虽然动物生来就有保护性免疫系统，但即使是先天免疫系统也从出生到成年都在发育，这种发育可能会受到性别和生长的影响。然而，大多数知识来自圈养动物或长寿缓慢生长的物种。此外，关于先天免疫功能（重要的第一道防线）如何在快速生长的动物（如自由生活的雀形目）的早期发育中知之甚少。我们研究了自由生活寒鸦Corvus monedula雏鸟的先天基线免疫功能的发展. 我们在孵化后第 12 天和第 29 天测量了四个免疫参数（溶血、血凝、细菌杀伤能力、触珠蛋白浓度）和结构体大小（体重、翼长、跗骨长度）。我们发现四分之三的免疫参数（溶血、血凝、细菌杀灭能力）随着雏鸟年龄的增长而显着增加，并且在雏鸟前不久大致达到成年水平。我们发现男性和女性之间的免疫发育几乎没有差异，尽管它们的结构发育不同。我们也没有发现任何证据表明雏鸟会在免疫发育与生长之间进行权衡。