Priorities for Future Research

Northern migratory populations of Yellow Warblers have been rewarding subjects of study during the breeding season, but with over 7 months on wintering grounds (Keast 1980), much work needs to be done to obtain an equivalent level of detail on the wintering birds. Especially useful would be information on age- and sex-specific survival, habitat partitioning, site fidelity, and within-year site persistence in winter. Data on natal and breeding dispersal are generally lacking, as are studies of migratory stopover ecology in this species. Identification of nonbreeding grounds for specific breeding populations and, ideally, tracking of individuals through their annual cycle, might allow an understanding of the relationship between single-broodedness and rapid departure from the breeding grounds and inter- and intraspecific dominance on the nonbreeding grounds. A detailed study of molt ecology at northern limits of the breeding range would complement research from more southerly sites. Factors regulating populations need to be better understood, as do trends in population numbers and conservation status of populations in different parts of the breeding and wintering ranges. More studies on behavioral correlates of plumage variation at different sites are needed to clarify the role chestnut streaking serves as badges in this species.

Full description of call notes based on sonagraphic analysis and of visual displays based on video analysis, including analysis of variation within and among call and display categories, and a formal analysis of behavioral and contextual correlates of calls and displays on both breeding and nonbreeding grounds, would complement the understanding of singing behavior to provide a fuller picture of the communication system of this species.

Taxonomy within this species is not at all clear. DNA samples from Mexican populations are needed to provide a more comprehensive understanding of relationships among all populations of Yellow Warbler.