Hepp Gary R, Kennamer Robert A
School of Forestry and Wildlife Sciences, Auburn University, Auburn, Alabama, United States of America.
Savannah River Ecology Laboratory, Aiken, South Carolina, United States of America.
PLoS One. 2018 Jan 26;13(1):e0191832. doi: 10.1371/journal.pone.0191832. eCollection 2018.
Incubation starts during egg laying for many bird species and causes developmental asynchrony within clutches. Faster development of late-laid eggs can help reduce developmental differences and synchronize hatching, which is important for precocial species whose young must leave the nest soon after hatching. In this study, we examined the effect of egg laying sequence on length of the incubation period in Wood Ducks (Aix sponsa). Because incubation temperature strongly influences embryonic development rates, we tested the interactive effects of laying sequence and incubation temperature on the ability of late-laid eggs to accelerate development and synchronize hatching. We also examined the potential cost of faster development on duckling body condition. Fresh eggs were collected and incubated at three biologically relevant temperatures (Low: 34.9°C, Medium: 35.8°C, and High: 37.6°C), and egg laying sequences from 1 to 12 were used. Length of the incubation period declined linearly as laying sequence advanced, but the relationship was strongest at medium temperatures followed by low temperatures and high temperatures. There was little support for including fresh egg mass in models of incubation period. Estimated differences in length of the incubation period between eggs 1 and 12 were 2.7 d, 1.2 d, and 0.7 d at medium, low and high temperatures, respectively. Only at intermediate incubation temperatures did development rates of late-laid eggs increase sufficiently to completely compensate for natural levels of developmental asynchrony that have been reported in Wood Duck clutches at the start of full incubation. Body condition of ducklings was strongly affected by fresh egg mass and incubation temperature but declined only slightly as laying sequence progressed. Our findings show that laying sequence and incubation temperature play important roles in helping to shape embryo development and hatching synchrony in a precocial bird.
对于许多鸟类物种来说，孵化在产卵过程中就已开始，并导致一窝蛋内出现发育异步现象。后产蛋的更快发育有助于减少发育差异并使孵化同步，这对于早成雏物种很重要，因为它们的幼雏在孵化后不久就必须离巢。在本研究中，我们研究了产卵顺序对林鸳鸯（Aix sponsa）孵化期长度的影响。由于孵化温度强烈影响胚胎发育速度，我们测试了产卵顺序和孵化温度对后产蛋加速发育并使孵化同步能力的交互作用。我们还研究了更快发育对雏鸭身体状况的潜在代价。收集新鲜蛋并在三个生物学相关温度下孵化（低温：34.9°C，中温：35.8°C，高温：37.6°C），并使用从1到12的产卵顺序。随着产卵顺序推进，孵化期长度呈线性下降，但这种关系在中温下最强，其次是低温和高温。在孵化期模型中纳入新鲜蛋重几乎没有得到支持。在中温、低温和高温下，第1枚蛋和第12枚蛋之间孵化期长度的估计差异分别为2.7天、1.2天和0.7天。只有在中等孵化温度下，后产蛋的发育速度才会充分增加，以完全补偿在完全孵化开始时林鸳鸯一窝蛋中所报道的自然发育异步水平。雏鸭的身体状况受到新鲜蛋重和孵化温度的强烈影响，但随着产卵顺序推进仅略有下降。我们的研究结果表明，产卵顺序和孵化温度在塑造早成雏鸟类的胚胎发育和孵化同步方面发挥着重要作用。
