Data from: “Green incubation”: avian offspring benefit from aromatic nest herbs through improved parental incubation behaviour

Development of avian embryos requires thermal energy, usually from parents. Parents may however trades off catering for embryonic requirements against their own need to forage through intermittent incubation. This dynamically adjusted behaviour can be affected by properties of the nest. Here we experimentally show a novel mechanism by which parents, through incorporation of aromatic herbs into nests, effectively modify their incubation behaviour to the benefit of their offspring. Our study species, the European starling, includes in its nest aromatic herbs which promote offspring fitness. We provided wild starlings with artificial nests including or excluding the typically selected fresh herbs and found strong support for our prediction of facilitated incubation. Herb effects were not explained by thermal changes of the nests per se, but by modified parental behaviours. Egg temperatures and nest attendance were higher in herb than herbless nests, egg temperatures dropped less frequently below critical thresholds, and parents started their active day earlier. These effects were dynamic over time and particularly strong during early incubation. Incubation period was shorter in herb nests, and nestlings were heavier one week after hatching. Aromatic herbs hence influenced incubation in beneficial ways for offspring, possibly through pharmacological effects on incubating parents.

鸟类胚胎的发育依赖热能，此类热能通常由亲鸟提供。然而亲鸟需在满足胚胎发育的热能需求与自身觅食需求之间做出权衡，这一权衡通过间断性孵卵行为得以实现。这种动态调控的孵卵行为会受到巢箱特性的影响。本研究通过实验揭示了一种全新机制：亲鸟可通过在巢箱中添加芳香草本植物，有效调整自身孵卵行为，从而为后代带来益处。本次研究的对象为欧洲椋鸟，该物种的巢内会出现可提升后代适合度的芳香草本植物。我们为野生欧洲椋鸟提供了分别添加或不添加该物种常规选取的新鲜芳香草本的人工巢箱，结果为“草本植物可促进孵卵行为”这一预测提供了强有力的支持证据。草本植物的影响并非源于巢箱本身的温度变化，而是源于亲鸟行为的改变。相较于无草本的巢箱，添加草本的巢箱中卵温与亲鸟巢驻留率更高，卵温低于临界阈值的频率更低，且亲鸟每日活动起始时间更早。此类影响随时间呈现动态变化，且在孵卵早期尤为显著。添加草本的巢箱中孵卵期更短，雏鸟出壳一周后的体重也更高。由此可见，芳香草本植物通过对孵卵亲鸟产生潜在的药理作用，以对后代有益的方式调控了孵卵过程。