Ligon Russell A, Hill Geoffrey E
Department of Biological Sciences, 331 Funchess hall, Auburn University, Auburn, AL 36849, USA.
Behav Ecol. 2010 May;21(3):456-464. doi: 10.1093/beheco/arq002. Epub 2010 Feb 10.
The relative amount of resources that avian parents provide to individual offspring within a brood represents a strategy that can have large effects on reproductive success. We tested whether parental feeding decisions of eastern bluebirds Sialia sialis are influenced by offspring plumage color by presenting pairs of differently colored fledglings side by side and observing how they were provisioned by parents. After a control period, we manipulated blue plumage color so that one sibling in each trial became relatively dark and one became relatively bright. During neither the control nor the experimental periods did either parent consistently feed naturally brighter or experimentally brightened sons more than drab sons. Under specific circumstances, however, both parents directed a higher proportion of their feeding attempts to more brightly colored sons. Paternal feeding attempts to brighter offspring during both the control and experimental periods increased in relation to the brightness of these fledglings relative to their brothers. Maternal feeding decision, on the other hand, were influenced by numerous variables during control and experimental periods including the date of the trial, the difference in mass between fledglings, the feeding behavior of fathers during the trial, the relative investment by fathers during the nestling stage, and the amount of UV chroma in fledgling plumage. Taken together, these results suggest that equal provisioning of offspring is the strategy most commonly adopted by eastern bluebirds but more brightly colored offspring will be fed preferentially when resources for offspring are limited.
鸟类父母为一窝雏鸟中的单个后代提供的资源相对数量，是一种可能对繁殖成功率产生重大影响的策略。我们通过将不同颜色的雏鸟并排展示，并观察它们如何被父母喂食，来测试东部蓝鸲（Sialia sialis）的父母喂食决策是否受到后代羽毛颜色的影响。在一个对照期之后，我们对蓝色羽毛颜色进行了处理，使每个试验中的一只雏鸟相对变深，另一只相对变亮。在对照期和试验期内，父母都没有始终如一地给天生颜色较亮或经实验变亮的雏鸟喂食多于颜色暗淡的雏鸟。然而，在特定情况下，父母双方都将更高比例的喂食尝试指向了颜色更鲜艳的雏鸟。在对照期和试验期内，父亲对较亮雏鸟的喂食尝试相对于这些雏鸟相对于其兄弟的亮度有所增加。另一方面，母亲的喂食决策在对照期和试验期内受到众多变量的影响，包括试验日期、雏鸟之间的体重差异、试验期间父亲的喂食行为、雏鸟阶段父亲的相对投入以及雏鸟羽毛中的紫外色度。综合来看，这些结果表明，平等地为后代提供食物是东部蓝鸲最常采用的策略，但当用于后代的资源有限时，颜色更鲜艳的后代将被优先喂食。
