Instead Kroodsma has provided a meticulous compendium of what is now knowable through the prism of individual experience about the singing of oscines
and suboscines in the context of their life cycles and environments.
In general, Suboscines Passerine birds are more closely-related to forested landscapes, and Oscines usually are more linked to open areas (Willis, 1979; Sick, 1997).
A total of 71 Passerine bird species from 11 families were sampled, and 30 had at least 10 captures, from which twenty (66.7%) were Suboscine, and 10 (33.4%) Oscine Passerines.
However hybridization is relatively frequent among passerines, specifically the oscines
, where song differences between species are ubiquitous and song is learned (Marler and Peters 1977; Marler 1987; Searcy et al.