Priorities for Future Research

The global population of the Connecticut Warbler is declining and climate change could exacerbate these trends (72 Stralberg, D., and E. Bayne (2013). Modeling avifaunal responses to climate change across Alberta’s natural regions. Alberta Biodiversity Monitoring Institute, Edmonton, AB, Canada. Close , 259 Rosenberg, K. V., J. A. Kennedy, R. Dettmers, R. P. Ford, D. Reynolds, J. D. Alexander, C. J. Beardmore, P. J. Blancher, R. E. Bogart, G. S. Butcher, A. F. Camfield, A. Couturier, D. W. Demarest, W. E. Easton, J. J. Giocomo, R. H. Keller, A. E. Mini, A. O. Panjabi, D. N. Pashley, T. D. Rich, J. M. Ruth, H. Stabins, J. Stanton, and T. Will (2016). Partners in Flight Landbird Conservation Plan: 2016 Revision for Canada and Continental United States. Partners in Flight Science Committee. Close , 261 Grinde, A. R., N. G. Walton, J. D. Bednar, A. L. Liljenquist, and S. Kolbe (2018). Minnesota National Forest breeding bird monitoring program annual report 1995–2018. Minnesota Digital Conservancy, University of Minnesota, Duluth, MN, USA. Close ). The primary driver of population declines is believed to be habitat loss and fragmentation on the breeding grounds (64 Hallworth M. T., E. Bayne, E. McKinnon, O. Love, J. A. Tremblay, B. Drolet, J. Ibarzabal, S. Van Wilgenburg, and P. P. Marra (2021). Habitat loss on the breeding grounds is a major contributor to population declines in a long-distance migratory songbird. Proceedings of the Royal Society B 288(1949). Close ). Therefore, basic information on breeding biology and the effects of land-use practices on breeding birds from throughout the range should be a priority. We have learned a great deal more about the breeding biology of the Connecticut Warbler from work by Marie Christine Saulnier (27 Saulnier, M-C. (2011). Biologie de la reproduction de la Paruline à gorge grise (Oporornis agilis) dans les pinèdes grises du Lac-Saint-Jean, Canada. M.S. thesis, Université du Québec à Chicoutimi, Chicoutimi, QC, Canada. Close ). Her use of new technologies such as digital video recording cameras placed at various nest sites and STR-1000 telemetry receivers attached to males and females have provided interesting details about parental behavior (e.g., incubation, brooding), nest sanitation, and division of labor among the sexes. However, details are still lacking on nest site selection, nest construction, fledgling and immature stages, post-breeding dispersal, nest predators, and more. Saulnier’s (27 Saulnier, M-C. (2011). Biologie de la reproduction de la Paruline à gorge grise (Oporornis agilis) dans les pinèdes grises du Lac-Saint-Jean, Canada. M.S. thesis, Université du Québec à Chicoutimi, Chicoutimi, QC, Canada. Close ) research was conducted in mature jack pine (Pinus banksiana) forests in Quebec to assess the possible impact of blueberry farming on breeding birds. In other parts of the breeding range, the majority of the global population breeds in spruce‒tamarack bogs, muskeg, and aspen‒poplar woodlands. More information is needed from these breeding populations which have different ecological requirements and are exposed to different land use practices.

Additional information is needed on the nonbreeding period of the annual cycle. The extent of the overwintering range is still poorly known and basic research is needed on habitat selection, diet, foraging behavior, social behavior, site fidelity, and abundance on the overwintering grounds. Although we have learned more about fall migration (128 McKinnon, E. A., C. Artuso, and O. P. Love (2017). The mystery of the missing warbler. Ecology 98:1970–1972. Close , 64 Hallworth M. T., E. Bayne, E. McKinnon, O. Love, J. A. Tremblay, B. Drolet, J. Ibarzabal, S. Van Wilgenburg, and P. P. Marra (2021). Habitat loss on the breeding grounds is a major contributor to population declines in a long-distance migratory songbird. Proceedings of the Royal Society B 288(1949). Close ), the routes of spring migration and stopover ecology in general need further study. Information for these periods of the annual cycle may uncover new threats that contribute to observed population declines.

Eastern and western breeding populations have very different ecological requirements. These distinct differences in habitat preferences could influence the evolution of eastern and western populations at the genetic and behavioral levels. Comparative research on mtDNA or nucDNA from eastern and western populations may uncover genetic differences. Different habitats affect sound transmission and cultural evolution of song. Comparing physical parameters of song (e.g., frequency, duration variables) and habitat differences between eastern and western populations may reveal the extent to which acoustic adaptation has occurred and influenced the cultural evolution of song.

Although we now know that there is individual variation in song among males at the microgeographic (204 Bergeron, S. (2020). Variabilité du chant de la paruline à gorge grise (Oporornis agilis). M.S. thesis, Université du Québec à Chicoutimi, Chicoutimi, QC, Canada. Close ) and macrogeographic (205 Hannah, K. C., E. M. Bayne, and N. V. Sanchez (2020). First description of the structure and geographic patterns in the songs of the Connecticut Warbler (Oporornis agilis). Wilson Journal of Ornithology 132:598–607. Close ) levels, the remainder of the vocal repertoire is poorly known. We are still lacking vocal analyses of call notes used in a variety of different behavioral contexts including male‒male territorial aggression, male‒female pre- and post-copulatory contact, anti-predator behavior, parent‒young contact, food-begging of young, etc.