Getting a Head Start: Diet, Sub-Adult Growth, and Associative Learning in a Seed-Eating Passerine

Abstract

Developmental stress, and individual variation in response to it, can have important fitness consequences. Here we investigated the consequences of variable dietary protein on the duration of growth and associative learning abilities of zebra finches, Taeniopygia guttata, which are obligate graminivores. The high-protein conditions that zebra finches would experience in nature when half-ripe seed is available were mimicked by the use of egg protein to supplement mature seed, which is low in protein content. Growth rates and relative body proportions of males reared either on a low-protein diet (mature seed only) or a high-protein diet (seed plus egg) were determined from body size traits (mass, head width, and tarsus) measured at three developmental stages. Birds reared on the high-protein diet were larger in all size traits at all ages, but growth rates of size traits showed no treatment effects. Relative head size of birds reared on the two diets differed from age day 95 onward, with high-diet birds having larger heads in proportion to both tarsus length and body mass. High-diet birds mastered an associative learning task in fewer bouts than those reared on the low-protein diet. In both diet treatments, amount of sub-adult head growth varied directly, and sub-adult mass change varied inversely, with performance on the learning task. Results indicate that small differences in head growth during the sub-adult period can be associated with substantial differences in adult cognitive performance. Contrary to a previous report, we found no evidence for growth compensation among birds on the low-protein diet. These results have implications for the study of vertebrate cognition, developmental stress, and growth compensation.

No Trade-Offs between Lipid Stores and Structural Growth in Juvenile Zebra Finches Undergoing Nutritional Stress during Development

“…Differing from previous studies, we found that tarsus length was not affected by nutritional conditions during development (Boag et al 1987;Arnold et al 2007;Honarmand et al 2010;Bonaparte et al 2011;Krause and Naguib 2014). The reason for this discrepancy may lie in the fact that all of the prior studies cited, apart from Krause and Naguib (2014), manipulated protein content.…”

“…Zebra finch (Taeniopygia guttata) and blue tit (Parus caeruleus) young that experienced poor nutritional conditions during the nestling stage showed a reduction in the rate of tarsus growth, an estimate of structural body size (e.g., Boag 1987;Limbourg et al 2004;Arnold et al 2007;Honarmand et al 2010;Bonaparte et al 2011;Krause and Naguib 2014). Although this seems to support the predictions of the tissue allocation hypothesis, these studies did not collect concurrent body fat data, so it is unclear what the relative investment in tarsus growth was compared to body fat accumulation.…”

Brain size and urbanization in birds

“…The higher degree of left skew in brain mass in urban habitats suggests that quality or quantity of food in urban environments does not allow all individuals to develop normal sized brains. Experimental studies based on variation in quality of food support this assumption (Bonaparte et al 2011). Because normal brain development requires large amounts of antioxidants, the low levels of vitamin E in livers of urban compared to rural birds ) may cause a large fraction of individuals developing small-sized brains.…”

Developmental stress: evidence for positive phenotypic and fitness effects in birds

“…Developmental stress may create resource trade-offs that cause individuals to invest in some neural structures at the expense of others during development (e.g., Sewall et al 2013). In this scenario, developmental stress may decrease some types of learning (e.g., song learning), but increase other types (e.g., motoric learning, but see Bonaparte et al 2011;Kitaysky et al 2003). In stressful environments, trade-offs in types of learning may benefit survival at early life-history stages at the expense of reproductive success in later life-history stages.…”