Breeding bird density does not drive vocal individuality

Abstract

Many species produce individually specific vocalizations and sociality is a hypothesized driver of such individuality. Previous studies of how social variation influenced individuality focused on colonial or non-colonial avian species, and how social group size influenced individuality in sciurid rodents. Since sociality is an important driver of individuality, we expected that bird species that defend nesting territories in higher density neighborhoods should have more individually-distinctive calls than those that defend nesting territories in lower-density neighborhoods. We used Beecher’s information statistic to quantify individuality, and we examined the relationship between bird density (calculated with point-counts) and vocal individuality on seven species of passerines. We found non-significant relationships between breeding bird density and vocal individuality whether regressions were fitted on species values, or on phylogenetically-independent contrast values. From these results, we infer that while individuality may be explained by social factors, breeding bird density is unlikely to be generally important in driving the evolution of individually-specific vocalizations.

Coexisting good neighbours: acoustic and calling microhabitat niche partitioning in two elusive syntopic species of balloon frogs, Uperodon systoma and U. globulosus (Anura: Microhylidae) and potential of individual vocal signatures

“…The study successfully demonstrated that there is a potential for individual recognition by individual vocal signatures in both species. The values of the Beecher’s index of total capacity information for both species were moderate compared to other anurans [ 5 ] and birds [ 45 ], however, this needs further assessment. A clear acoustic and microhabitat niche partitioning between the two syntopic species may be related to pre-zygotic isolation, character displacement and assortative mating strategy in the two species.…”

“…Most call properties are significantly different among individuals in both of the focal Uperodon species, highlighting a potential to identify individual by their calls. The total information capacity [ 34 ] for both Uperodon systoma (3.83 bits; ~ 14 individuals distinguishable) and U. globulosus (4.69 bits; ~ 26 individuals distinguishable) are relatively low compared to other anurans species such as Nidirana adenopleura (7.3 bits; ~ 158 distinguishable individuals [ 5 ];) and birds such as the Lazuli buntings ( Passerina amoena ; 10.6 bits; ~ 1552 distinguishable individuals [ 45 ];). This difference in information capacity between the two Uperodon species may result from a preference for breeding in small rainwater puddles which cannot accommodate a large number of calling individuals due to their small size.…”