Although it has long been known that juveniles often have foraging skills inferior to those of adults, it has generally been assumed that animal prey are more difficult to capture than fruit, and thus that juveniles foraging on fruit should be similar to adults in their efficiency. To examine these ideas, we investigated the abilities of juvenile and adult American robins Turdus migratorius to forage for ground invertebrates and fruits of the black cherry tree Prunus serotina. We hypothesized that juveniles, lacking the experience of adults, would not have the skills of adults and therefore would be less proficient invertebrate and fruit foragers. Juveniles captured 69% of invertebrates at which they struck compared with 80% of adults’ strikes that ended in capture. However, juveniles made more strikes than adults, so mean prey capture per minute was the same. Juveniles were also less skilled fruit foragers. Juveniles were twice as likely as adults to fail to pick a cherry (55% of adults’ vs. 28% of juveniles’ attempts ended in success). However, there was no significant difference in the proportion of juveniles and adults that dropped a cherry once it was picked. As a result of their low levels of success, juveniles consumed about half the number of cherries per minute as did adults. Contrary to prior assumptions, skills involved in fruit foraging may not be so easily acquired and many omnivorous species, like the American robin, must learn both invertebrate and fruit foraging skills.
Juvenile birds lack the experience of adults and, as a result, are typically less efficient foragers. Environmental factors can influence how birds forage and the outcome of foraging bouts, but few investigators have considered the effects of such factors on the foraging behavior of juveniles. We examined the effects of two environmental factors, sunlight and soil moisture, on the foraging behavior of juvenile and adult American Robins (Turdus migratorius). Both factors had a significant effect on robin foraging, with robins more effective at capturing arthropods in the sun and worms in moist soils. However, juveniles were less successful than adults across all conditions. Juveniles were less successful than adults at capturing arthropods and were less efficient at capturing worms. Juveniles captured an average of one worm per minute, whereas adults captured nearly two worms per minute. Additionally, the high failure rates of juveniles (0.44/min) as compared to adults (0.20/min) may be indicative of their inability to choose suitable prey items. Finally, we found that juveniles tended to forage with other robins more than did adults, suggesting that they may use other individuals as cues for locating favorable foraging sites.
Abstract:The behavior of foragers can directly affect the dispersal of seeds. Strangler figs are keystone resources throughout the tropics and are important resources for both primates and birds. We examined the foraging behavior of golden-handed tamarins and four bird species in a strangler fig to see how these behaviors might affect the dispersal of fig seeds. Tamarins removed fruit at a faster rate than did any of the bird species examined. Additionally, tamarins tended to swallow figs whole whereas birds tended to drop figs once they were processed. Resumen: El comportamiento de foragers puede afectar directamente la dispersión de semillas. Los higos del estrangulador son recursos trapezoidales a través de las zonas tropicales y son recursos importantes para los primates y los pájaros. Examinamos el comportamiento del forraje de tamarins de oro-dados y cuatro especies del pájaro en un higo del estrangulador para ver cómo estos comportamientos pudieron afectar la dispersión de las semillas del higo. Fruta quitada Tamarins en una tarifa más rápida que la especie ua de los del pájaro examinada. Además, los tamarins tendieron para tragar los higos enteros mientras que los pájaros tendieron para caer los higos que fueron procesados una vez. Los árboles de higo de Tamarins que visitan injieren cantidades grandes de semillas del higo que se puedan depositar a través del bosque. Los pájaros por otra parte tendieron para procesar lentamente las frutas cerca del árbol de higo y la gota procesó la fruta que contenía cantidades grandes de semillas. Los estudios futuros necesitan ser conducidos para comprobar diferencias en sino de la semilla de la dispersión del poste. Palabras-clave: frugivores, nivel de entrada, manakins, calidad de la dispersión de la semilla, tamarins, tanagers. Biota Neotrop., vol. 9, no. 3 We observed one strangler fig (Ficus sp.) that was approximately 12 m tall with a crown that was 12 m in diameter. The fig was located alongside a park road making observations of foraging behavior ideal; the majority of the tree crown and fruits were visible from the road. Fruits were small (1.18 ± 0.04 cm) and aggregated in clusters on terminal branches. Fruits were abundant throughout the study (crop size > 1,000) and the majority of the fruits (>75%) were unripe and green in color; ripe fruit was reddish-purple in color.Our observations were made during the rainy season from July 17 through July 25, 2008, at the beginning of a period of fruit scarcity for the site (De Dijn et al. 2007). Observations were made between approximately 06:30 AM and 05:00 PM. Over the nine days, we recorded which primates and birds foraged in the tree. We calculated the total visits per species and the average number of visits per day. For the following analyses we included only species that visited tree or more than one day; therefore we only included tamarins and four bird species. In order to understand how primate and bird visitation affected fruit removal we calculated foraging bout length for tamarins and birds, as well a...
Temporally coordinated interactive vocalizations are important means of communication between individuals in various animal taxa. In mammals, interactive calling and singing can be highly synchronized to create either overlapping or antiphonal duets while in others, competitors antagonistically vocalize, engaging in counter-singing. Among non-primate mammals these vocalizations are considered rare and poorly understood. We provide an overview of antiphonal calling, duetting and counter-singing in non-primate mammals. Many of these coordinated vocalizations play a role in social interactions and allow mammals to convey information to other members of the social unit in visually inaccessible environments. South American Bamboo rats Dactylomys spp. are arboreal bamboo specialists found in dense bamboo thickets in Bolivia, Peru, Ecuador, Brazil and Colombia. These nocturnal rodents are rarely seen but can be easily heard because of their loud and distinctive staccato vocalizations. We provide some evidence that Bamboo rats engage in duetting, and as such they provide another case of a mammalian species, in which to investigate temporally coordinated interactive singing. We urge researchers to work toward common definitions of temporally coordinated vocalizations and to search for more mammals that utilize such vocalizations.
Alarm calls are important signals that allow individuals to convey information about both predator type and risk level. How individuals respond to these calls may depend on both the intensity of the call as well as the age of the responder. We investigated an aerial alarm call of the American robin and specifically examined how call rate (reflecting intensity) and age affect the anti-predator behaviors of responders. Both juveniles and adults significantly altered their behavior upon hearing playbacks of seet calls; they foraged less and increased vigilance and other anti-predator behaviors. Adult robins were also able to distinguish between low intensity and high intensity calls; skygazing, an important behaviour that allows robins to scan for raptors, increased with call rate. Juveniles, on the other hand, skygazed less and there was a trend for juveniles to spend more time alert than adults suggesting that some learning may be involved.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.