When successive stages of an organism's life-history overlap, conflicts and trade-offs can emerge due to competition among physiological pathways. For example, long periods of sustained locomotion in migrating birds are supported by the androgenic up-regulation of aerobic factors, such as new red blood cell production and hematocrit. However, towards the end of migration, many female birds begin up-regulating 17ß-estradiol (E₂) to support vitellogenesis and egg production, but E₂ secretion is known to have suppressive effects on red blood cell production (anti-erythropoiesis). We explored potential trade-offs between factors related to aerobic performance (hematocrit, reticulocyte index) and the expression of factors related to E₂-mediated vitellogenesis (i.e. yolk precursor production) in female macaroni penguins (Eudyptes chrysolophus), a species in which the physiologies controlling egg production and migratory activity run simultaneously (e.g. females experience a migratory conflict). We collected blood samples from penguins immediately upon their return to the colony, prior to egg laying. Hematocrit was elevated when the penguins returned to the colony (50.05% ± 3.40 SD), which is similar to pre-laying values observed in other migratory bird species. Furthermore, mean reticulocyte levels were elevated (34.87% ± 2.34), which is the highest level yet recorded in birds. Similarly, both plasma vitellogenin and yolk-targeted very low density lipoprotein levels were upregulated (2.30 ± 0.06 μg Zn ml⁻¹, and 9.70 ± 0.19 mmol l⁻¹, respectively), indicating that penguins were reproductively active and producing eggs during migration and upon arrival on land. As predicted, a negative relationship between hematocrit and plasma vitellogenin was found, but we found no evidence to suggest that birds were experiencing reproductive anemia. Alternatively, we attribute the negative relationship to a hemodilution effect of yolk precursor secretion into circulation. It appears that female macaroni penguins are able to preserve hematocrit levels and new red blood cell production when migratory activity overlaps with reproductive processes.

当生物的生命史的连续阶段重叠时，由于生理途径之间的竞争，可能会出现冲突和折衷。例如，在迁徙的鸟类中长期持续的运动受到有氧因子的雄激素上调的支持，例如新红细胞的产生和血细胞比容。然而，在迁徙即将结束时，许多雌鸟开始上调17β-雌二醇（E ₂）以支持卵黄发生和卵子产生，但是已知E ₂分泌对红细胞产生具有抑制作用（抗红细胞生成）。我们探讨了有氧运动相关因素（血细胞比容，网织红细胞指数）与E ₂相关因子表达之间的潜在权衡雌通心粉企鹅（Eudyptes chrysolophus）中介导的卵黄发生（即卵黄前体产生），该物种中控制卵子生产和迁徙活动的生理同时进行（例如雌性经历迁徙冲突）。我们在产卵前立即从企鹅返回殖民地时收集它们的血样。当企鹅返回殖民地时，血细胞比容升高（50.05％±3.40 SD），这与在其他候鸟物种中观察到的预产值相似。此外，网织红细胞的平均水平升高（34.87％±2.34），这是鸟类所记录的最高水平。同样，血浆卵黄蛋白原和以卵黄为靶的极低密度脂蛋白水平均被上调（2.30±0.06μgZn ml ^-1，和分别为9.70±0.19 mmol l ^-1），表明企鹅在繁殖过程中以及到达陆地后具有生殖活性并产卵。如预期的那样，发现血细胞比容和血浆卵黄蛋白原之间存在负相关关系，但我们没有发现证据表明鸟类正在经历生殖性贫血。或者，我们将这种负相关性归因于卵黄前体分泌进入循环的血液稀释作用。当迁徙活动与生殖过程重叠时，雌通心粉企鹅似乎能够保持血细胞比容水平和新的红细胞产生。