Karl S. Berg

Vertical transmission of learned signatures in a wild parrot

Learned birdsong is a widely used animal model for understanding the acquisition of human speech. Male songbirds often learn songs from adult males during sensitive periods early in life, and sing to attract mates and defend territories. In presumably all of the 350+ parrot species, individuals of both sexes commonly learn vocal signals throughout life to satisfy a wide variety of social functions. Despite intriguing parallels with humans, there have been no experimental studies demonstrating learned vocal production in wild parrots. We studied contact call learning in video-rigged nests of a well-known marked population of green-rumped parrotlets (Forpus passerinus) in Venezuela. Both sexes of naive nestlings developed individually unique contact calls in the nest, and we demonstrate experimentally that signature attributes are learned from both primary care-givers. This represents the first experimental evidence for the mechanisms underlying the transmission of a socially acquired trait in a wild parrot population.

Contact calls are used for individual mate recognition in free-ranging green-rumped parrotlets, Forpus passerinus

Contact calls function to coordinate movements in a wide variety of social animals. Where population density is high, visibility is low and repeated interactions occur between known social companions, calls are often individually recognizable. Parrots are highly social and make substantial daily movements, which appear to be mediated through contact calling. However, there is little experimental evidence for how free-ranging parrots recognize social companions. We quantified intra- and interindividual variation of contact calls in a banded population of green-rumped parrotlets in Venezuela. Recordings of a sample of males were made on replicate days as they announced their return to incubating mates. Spectrographic structure of these contact calls showed significantly more variation between than within individuals, and calls could be correctly classified to individuals more often than was expected by chance. Males varied across multiple dimensions simultaneously, including duration, frequency and frequency modulation of contact calls. Playback experiments showed that free-ranging female parrotlets responded significantly more often to their mates’ calls than to calls of males of other nests. Mate recognition via contact calls may be selectively advantageous during incubation and brooding if this reduces the potential costs associated with confusing contact calls of mates with those of nonmates, including infanticidal conspecifics.

Factors shaping the ontogeny of vocal signals in a wild parrot

SUMMARY Parrots rely heavily on vocal signals to maintain their social and mobile lifestyles. We studied vocal ontogeny in nests of wild green-rumped parrotlets (Forpus passerinus) in Venezuela. We identified three successive phases of vocal signaling that corresponded closely to three independently derived phases of physiological development. For each ontogenetic phase, we characterized the relative importance of anatomical constraints, motor skills necessary for responding to specific contexts of the immediate environment, and the learning of signals that are necessary for adult forms of communication. We observed shifts in the relative importance of these three factors as individuals progressed from one stage to the next; there was no single fixed ratio of factors that applied across the entire ontogenetic sequence. The earliest vocalizations were short in duration, as predicted from physical constraints and under-developed motor control. Calls became longer and frequency modulated during intermediate nestling ages in line with motor skills required for competitive begging. In the week before fledging, calls drastically shortened in accordance with the flight-constrained short durations of adult contact calls. The latter constraints were made evident by the demonstrated links between wing-assisted incline running, a widespread prelude to avian flight, just before the shift from long-duration begging calls to short-duration contact calls. At least in this species, the shifting emphases of factors at different ontogenetic stages precluded the morphing of intermediate-stage begging calls into adult contact calls; as shown previously, the latter are influenced by sample templates provided by parents.

NOTES ON THE NATURAL HISTORY OF THE PALE-MANDIBLED ARAÇARI

Abstract The little-known Pale-mandibled Araçari is endemic to wet forests of western Ecuador. I quantified population density, feeding ecology, reproductive biology, and vocalizations. Population density in the study area was one group (nine individuals) per 333 ha. They were observed to consume fruits of 34 species of plants, of which Lauraceae and Palmae were the most important. Pale-mandibled Araçaris fed their young fruits from at least eight species of plants, insects from five orders, adult and nestling birds, and bird eggs. Nests were made in cavities within live trees, typically Carapa guianensis, and clutches consisted of at least two eggs. At one nest, incubation lasted approximately 17 d. Nestling care in one nest lasted at least 44 d, and was shared by the female, the male and at least one helper. Pale-mandibled Aracaris roosted in groups of up to seven individuals. Ninety-five percent of primary forest in the range of this species had been cut by 1988, and less than 1% of its original habitat lies within protected areas.

Parrots of the Wild: A Natural History of the World's Most Captivating Birds

Parrots of the Wild: A Natural History of the World’s Most Captivating Birds by Catherine A. Toft and Timothy F. Wright. 2015. University of California Press, Berkeley, CA, USA. 346 pp., ~1,000 references, 90 color photo plates, 15 graphs and tables.

Phylogenetic and ecological determinants of the neotropical dawn chorus

39.95 (hardcover and ebook). ISBN 9780520239258. Most readers of The Condor need little convincing of the importance of birds in a broader understanding of vertebrate ecology and evolutionary biology. There are more than 10,000 species that inhabit most parts of the world, and they exhibit a broad range of mating systems. Birds dominate terrestrial vertebrate communities and, as a result, are often the vertebrate barometer of choice for assessing ecosystem processes and health. Fewer readers may appreciate the fact that one group, the parrots, represents a microcosm of many important aspects of avian biology. The 371 recognized species of extant parrots are or were found in most parts of the planet and exhibit a diversity of mating strategies. They are famous for their extraordinary intelligence and show an order-of-magnitude range in brain sizes that rivals all other modern birds. The remarkable plasticity of parrot brains is also reflected in their size in relation to overall body size, among the highest in birds and a trait often found in animals with sophisticated cognitive ecologies. Their bizarre communicative abilities, well known in captivity and by millions of pet owners, represent an emerging model for comparisons with songbird neuroethology. Clearly, parrots are poised to provide information on an important dimension of avian biology. However, as Catherine Toft and Timothy Wright argue in Parrots of the Wild, parrot populations and species are disappearing at a truly alarming rate around the world, threatening to curtail an impor-