Abstract：
The peptide hormone prolactin plays an important role in the expression of parental care behaviours across bird and mammal taxa. While a great deal is known about how plasma prolactin concentrations vary across the reproductive cycle, the few studies that investigate how prolactin relates to individual-level variation in parental care have reported mixed results. We argue that, since parental care is also affected by social interactions and environmental constraints, prolactin may better reflect behaviours that are indirectly related to parenting than the absolute level of care that is eventually expressed. In this study, we tested for associations between plasma prolactin and the expression of both parental care and proximity to the partner in incubating black-headed gulls, Chroicocephalus ridibundus. Baseline prolactin levels increased with calendar date but were unrelated to incubation behaviours. However, parents who showed a weaker decrease in prolactin to an acute stressor spent more time in close proximity to their incubating partner while not on the nest themselves, suggesting that individual variation in stress-induced prolactin changes reflect differences in parents\' tendency to be closely associated with their partner and the joint nesting attempt. Baseline and stress-induced levels of the stress hormone corticosterone were unrelated to both prolactin levels and parental behaviours, suggesting that this hormone is not a strong moderator of parental care in black-headed gulls. One potential explanation for the link between prolactin dynamics and partner proximity is that prolactin reflects parental motivation to provide parental care or retain contact with the breeding partner, but further work is needed to directly test this hypothesis.
摘要：
肽激素催乳素在鸟类和哺乳动物分类群的父母照料行为表达中起重要作用。虽然人们对血浆催乳素浓度在整个生殖周期中的变化有很多了解，少数调查催乳素与父母照护中个体水平差异相关的研究报告了不同的结果.我们认为，由于父母的照顾也受到社会互动和环境限制的影响，与最终表达的绝对护理水平相比,催乳素可能更好地反映与育儿间接相关的行为.在这项研究中,我们测试了血浆催乳素与父母关怀和与伴侣在孵化黑头海鸥中的表达之间的关联，嗜头菌ridibundus。基线催乳素水平随日历日期而增加，但与孵化行为无关。然而,父母谁表现出较弱的催乳素下降到急性应激源花费更多的时间在靠近他们的孵化伙伴，而不是在巢自己，这表明应激诱导的催乳素变化的个体差异反映了父母与伴侣和联合筑巢尝试密切相关的倾向。基线和应激诱导的应激激素皮质酮水平与催乳素水平和父母行为无关，这表明这种激素不是黑头海鸥父母照顾的强有力的调节剂。催乳素动力学与伴侣亲近之间联系的一种潜在解释是，催乳素反映了父母提供父母照顾或与繁殖伴侣保持联系的动机，但是需要进一步的工作来直接检验这一假设。
