Early corticosterone increases vocal complexity in a wild parrot: An organizational role of the hypothalamic-pituitary-adrenal axis in vocal learning?

The neuroendocrinology of vocal learning is exceptionally well known in passerine songbirds. Despite huge life history, genetic and ecological variation across passerines, song learning tends to occur as a result of rises in gonadal and non-gonadal sex steroids that shape telencephalic vocal control circuits and song. Parrots are closely related but independently evolved different cerebral circuits for vocal repertoire acquisition in both sexes that serve a broader suite of social functions and do not appear to be shaped by early androgens or estrogens; instead, parrots begin a plastic phase in vocal development at an earlier life history stage that favors the growth, maturation, and survival functions of corticosteroids.

Vocal babbling in a wild parrot shows life history and endocrine affinities with human infants.

Prelinguistic babbling is a critical phase in infant language development and is best understood in temperate songbirds where it occurs primarily in males at reproductive maturity and is modulated by sex steroids. Parrots of both sexes are icons of tropical vocal plasticity, but vocal babbling is unreported in this group and whether the endocrine system is involved is unknown. Here we show that vocal babbling is widespread in a wild parrot population in Venezuela, ensues in both sexes during the nestling stage, occurs amidst a captive audience of mixed-aged siblings, and is modulated by corticosteroids.

Metabolic rate and specific dynamic action of the Red-legged Honeycreeper, a nectar-feeding Neotropical passerine.

Rate of oxygen consumption (VO(2)) and carbon dioxide production (VCO(2)) were measured in the Red-legged Honeycreeper (Cyanerpes cyaneus, mean body mass 14.0+/-0.1g) at ambient temperatures (T(a)) between 15 degrees C and 35 degrees C to determine the basal metabolic rate (BMR).

Seasonal variation in energy expenditure and body composition in captive White Storks (Ciconia ciconia).

North Western European populations of White Storks (Ciconia ciconia) appear to have been saved from extinction by settling, i.e. stopping migration.

Plasma corticosterone levels of semipalmated sandpiper Calidris pusilla overwintering in a tropical coastal lagoon of northeastern Venezuela: effect of capture and handling.

Semipalmated sandpiper Calidris pusilla arrives on the coasts of Venezuela between the middle of August and early September, staying there until May when birds prepare for vernal migration. To investigate possible relationships between corticosterone levels and body mass changes during preparation for migration, we sampled birds during wintering (January) and vernal premigration (May) over 2 years. Body mass and fat increased significantly from wintering to vernal premigration in both years.

Reliability in estimates of body composition of birds: oxygen-18 versus deuterium dilution.

Body composition in birds was evaluated indirectly by 18O and 2H dilution. Body composition was determined by whole-body chemical analysis of eight adult roosters (Gallus gallus). In vivo measurements of total body water (TBW) were carried out using doubly labeled water (2H2 18O).

Sugar preferences, absorption efficiency and water influx in a Neotropical nectarivorous passerine, the Bananaquit (Coereba flaveola).

Nectarivory has evolved repeatedly in a number of unrelated bird taxa throughout the world and nectar feeding birds, regardless of their taxonomic affiliation, display convergent foraging and food processing adaptations that allow them to subsist on weak sugar solutions. However, phylogeny influences sugar type preferences of nectarivores. We investigated sugar preferences, assimilation efficiency and water flux in a Neotropical honeycreeper, the Bananaquit (Coereba flaveola; Coerebidae), a member of a radiation of tanagers and finches.