Two questions in the research of animal personality—whether there is a correlation between a personality trait and individual reproductive success, and what is the genetic basis underlying a personality trait—remain unresolved. We addressed these two questions in three shrub-nesting birds, the Azure-winged Magpie (Cyanopica cyanus, AM), White-collared Blackbird (Turdus albocinctus, WB), and Brown-cheeked Laughingthrush (Trochalopteron henrici, BL). The personality type of an individual was first identified according to its response to a territorial intruder. Then, we compared the fleeing distance, breeding parameters, and differential expressed genes (DEGs) in the brain transcriptome between bold and shy breeders. In the three species, bold breeders exhibited more aggressiveness towards an intruder of their territory than did shy breeders. The reproductive success of bold breeders was significantly higher than that of shy breeders in AM but not in WB and BL. The three species shared one DEG, crabp1, which was up-regulated in bold relative to in shy individuals. By regulating the expression of corticotropin-releasing hormone, higher crabp1 gene expression can decrease cellular response to retinoic acid. Therefore, bold individuals are insensitive to external stresses and able to exhibit more aggressiveness to intruders than their shier counterparts. Aggressiveness is beneficial to bold individuals in AM but not in WB and BL because the former could evoke neighbors to make the same response of defending against intruders but the latter could not. Although a personality trait may have the same genetic basis across species, its correlation with reproductive success depends largely on the life history style of a species.
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Open Access
Research Article
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Open Access
Research
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Great diversity exists in the parenting pattern of altricial birds, which has long been considered as an adaptive response to specific environmental conditions but not to their life-history style.
We examined the egg-laying and nestling-raising pattern of the Grey-backed Shrike (Lanius tephronotus) that breeds only once a year on the Tibetan Plateau. We compared the dietary composition to that of its sympatric competitor, the Brown-cheeked Laughing Thrush (Trochalopteron henrici) that breeds twice a year.
Female Grey-backed Shrikes produced a fixed clutch size of five, with increasing egg size by their laying sequence. The last offspring in the brood is disadvantageous in the size hierarchy because it hatches later. However, they had the largest fledgling body mass. These findings indicate that Grey-backed Shrikes adopt the brood survival strategy in both the egg and nestling phases. Moreover, males and females exhibit no sexual division in providing parental care as they made an equal contribution to the total amount of food delivered to their brood. This parenting pattern of Grey-backed Shrikes, as well as their dietary items, differ significantly from those of the Brown-cheeked Laughing Thrush.
We suggest that the differentiation in life-history style between sympatric competitors, rather than a behavioral response to specific environmental conditions, plays a decisive role in driving avian parenting strategy diversification.
