Early ontogenetic effects on song quality in the Bengalese finch (Lonchura striata var. domestica): laying order, sibling competition, and song syntax

Like Father Like Son: Cultural and Genetic Contributions to Song Inheritance in an Estrildid Finch

Social learning of vocalizations is integral to song inheritance in oscine passerines. However, other factors, such as genetic inheritance and the developmental environment, can also influence song phenotype. The relative contributions of these factors can have a strong influence on song evolution and may affect important evolutionary processes such as speciation. However, relative contributions are well-described only for a few species and are likely to vary with taxonomy. Using archived song data, we examined patterns of song inheritance in a domestic population of Java sparrows (Lonchura oryzivora), some of which had been cross-fostered. Six-hundred and seventy-six songs from 73 birds were segmented and classified into notes and note subtypes (N = 22,972), for which a range of acoustic features were measured. Overall, we found strong evidence for cultural inheritance of song structure and of the acoustic characteristics of notes; sons’ song syntax and note composition were similar to that of their social fathers and were not influenced by genetic relatedness. For vocal consistency of note subtypes, a measure of vocal performance, there was no apparent evidence of social or genetic inheritance, but both age and developmental environment influenced consistency. These findings suggest that high learning fidelity of song material, i.e., song structure and note characteristics, could allow novel variants to be preserved and accumulate over generations, with implications for evolution and conservation. However, differences in vocal performance do not show strong links to cultural inheritance, instead potentially serving as condition dependent signals.

Oviposition drives hatching order and developmental disparities with brood mates

Birth or hatching order can affect fitness. It has long been assumed that the order in which a bird's egg is laid (its oviposition) and first exposed to incubation relative to other eggs in the nest determines the order in which it hatches and the subsequent effects on development and survival. To my knowledge, this cause of hatching order has not been tested while controlling for laying-order effects on egg composition. Like those of many species, the last-laid eggs in clutches of the Lincoln's sparrow ( Melospiza lincolnii) hatch last and produce nestlings with reduced growth and survival rates. Last-hatched Lincoln's sparrows also develop wider bills that are associated with reduced attractiveness of adult courtship songs. Using wild, free-ranging Lincoln's sparrows, I replaced the first or fourth freshly laid egg in four-egg host nests with a freshly laid first egg from a donor nest. I discovered that the experimental elevation of oviposition-which controlled for egg composition-delayed hatching, inhibited growth and widened bill gape, thus confirming the mechanism for hatching order and revealing a potential role for oviposition in reproductive success. Similar effects of postnatal family position could affect fitness in other taxa, as well.