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

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

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

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

Effects of diet and head width residual on number of bouts taken to perform the associative learning task.

<p>Level-one effects only: Model P: F = 15.51 (2,48 df), P<0.0001; adjusted R-squared = 0.367.</p

Relationship between bouts required to complete the learning task when yellow versus black curtains were associated with a food reward.

<p>(Open circles = LO diet birds; closed circles = HI diet birds. Means±S.E. for black reward: LO –16.67±1.47 (N = 9); HI—11.14 ±1.45 (N = 7).)</p

Distribution of number of bouts needed to pass the learning task as a function of diet.

<p>(White boxes–LO diet birds(mean±S.E.:20.32±1.57); black boxes–HI diet birds (mean±S.E.: 12.03±1.06). (For statistical effect, see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0023775#pone-0023775-t003" target="_blank">Tables 3</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0023775#pone-0023775-t004" target="_blank">4</a>.)</p

Effects of early growth variables on number of bouts taken to perform the associative learning task.

<p>Level-one effects only: Model P: F = 20.23 (3,38 df), P<0.0001; adjusted R-squared = 0.615.</p

Relationship between early growth (day55 to day 95) and bouts required to pass the learning task.

<p>a) head width; b) mass change. (White circles – LO diet birds; black circles – HI diet birds. For statistical effects, see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0023775#pone-0023775-t004" target="_blank">Table 4</a>.)</p

Relationship between residuals of the regression of head width on tarsus (day 175) and bouts taken to pass the learning task.

<p>(White circles–LO diet birds; black circles – HI diet birds. For statistical effect, see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0023775#pone-0023775-t003" target="_blank">Table 3</a>. )</p

Predators of bird nests in the Atlantic forest of Argentina and Paraguay

Predation is the major cause of avian nest failure, and an important source of  natural selection on life history traits and reproductive behavior. However, little is known about the identity of nest predators in much of the world, including the Neotropics. To identify some of the nest predators exerting selection pressure on birds of the subtropical Atlantic forest, we present observations of animals depredating bird nests in Argentina and Paraguay. We recorded depredations (destruction or removal of eggs or nestlings) at 33 nests of 25 species of birds, confirming as predators ten species of birds (Squirrel Cuckoo Piaya cayana, White-eared Puffbird Nystalus chacuru, Toco Toucan Ramphastos toco, Red-breasted Toucan Ramphastos dicolorus, Saffron Toucanet Pteroglossus baillonii, Chestnut-eared Aracari Pteroglossus castanotis, Planalto Woodcreeper Dendrocolaptes platyrostris, White-throated Woodcreeper Xiphocolaptes albicollis, Buff-browed Foliage-gleaner Syndactyla rufosuperciliata, and Plush-crested Jay Cyanocorax chrysops) and two species of medium-sized mammals (White-eared Opossum Didelphis albiventris and Crab-eating Fox Cerdocyon thous), and inferring two additional mammal species (Black Capuchin Monkey Sapajus nigritus and Southern Tigrina Leopardus guttulus). Fifty-five percent of these nests were depredated by toucans or aracaris (Ramphastidae), which destroyed eggs and nestlings at cup-, closed- and cavity-nests. Red-breasted Toucans destroyed nests 1.6?22 m high, in habitats ranging from primary forest to a backyard. Mammals and jays depredated nests from ground-level to midstory, whereas woodcreepers and aracaris depredated nests from the midstory to canopy. We did not record snakes at any bird nests, in strong contrast to studies from other Neotropical forests. Further studies should examine trade-offs among nest concealment, physical protection, and parental defense behavior as means of reducing nest predation, and use camera traps to quantify nest predation rates by predator species.Fil: Cockle, Kristina Louise. Proyecto Selva de Pino Paraná; Argentina. University of British Columbia; Canadá. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; Argentina. State University of Louisiana; Estados UnidosFil: Bodrati, Alejandro. Proyecto Selva de Pino Paraná; ArgentinaFil: Lammertink, J. Martjan. Provincia de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Universidad Autónoma de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción; Argentina. Cornell University; Estados Unidos. Proyecto Selva de Pino Paraná; ArgentinaFil: Bonaparte, Eugenia Bianca. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Proyecto Selva de Pino Paraná; ArgentinaFil: Ferreyra, Carlos. Proyecto Selva de Pino Paraná; ArgentinaFil: Di Sallo, Facundo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Proyecto Selva de Pino Paraná; Argentin