Passerine Pit Stops

30 September 2015 - By: Natalie Sopinka

Passerine Pit Stops

White-throated Sparrow-In text
White-throated sparrow

By Natalie Sopinka

Local site variation in stopover physiology of migrating songbirds near the south shore of Lake Ontario is linked to fruit availability and quality

Susan B. Smith, Allyson C. Miller, Charmaine R. Merchant, and Amie F. Sankoh
Conservation Physiology (2015) 3 (1): cov036 doi:10.1093/conphys/cov036

Autumn is a hectic time of the year for migratory songbirds. For blackpoll warblers (Setophaga striata) provisions need to be met in order to make the long-distance migration from breeding areas in Canada to overwintering grounds in South America. Are we there yet?! Migrating birds flying along northeastern USA take breaks to rest and refuel at stopover sites. To satisfy their omnivorous diet, stopping at stopover sites with abundant fruit-bearing plants is best. But with an ever-growing human presence, the abundance and diversity of plants at stopover sites is shifting. Alteration of stopover habitats may impact how much food is available for birds to forage, reducing energetic reserves. Inadequate fuel for the rest of their journey may compromise migration success.

Smith et al. (2015) investigated whether variation in plant diversity and abundance between two stopover sites reflected energetic profiles of blackpoll warbler and white-throated sparrow (Zonotrichia albicollis). The first site was the Braddock Bay Bird Observatory (BBBO), a known stopover site with an established bird monitoring program. This site, located along the southern shore of Lake Ontario, is in a deciduous forest. The second site was a wooded area near the Rochester Institute of Technology (RIT). This site was characterized by comparatively sparse vegetation and was proximate to human development. Surveys indicated that the diversity of plants, proportion of native plants, and abundance of ripe fruit was greater at the BBBO site. Arrowwood viburnum and gray dogwood were the most abundant fruit-producing plants at the BBBO site. These two species of plant had the highest energy density and percentage of fat compared to the other plants that were sampled at the stopover sites. Are the energy levels of birds higher at energy-rich pit stops? Plasma triglycerides were measured as this metabolite increases following feeding and fat deposition. Concentrations of plasma triglycerides were higher in birds caught at the BBBO site compared to birds caught at the RIT site, suggesting greater deposition of fat is occurring at the higher-quality stopover site.

Other landscape variables such as proximity to water or soil type may influence the quality of habitats birds stop at en route to their final winter destination. By coupling nutritional composition of plants with physiological condition, this study highlighted the importance of land management that ensures fruit-availability at passerine pit stops.

Article selected by Steven Cooke.

Category: Animal Biology
Natalie Sopinka

Natalie Sopinka

Natalie is a postdoctoral research fellow at the Great Lakes Institute for Environmental Research (Windsor, Canada). In collaboration with Yellow Island Aquaculture Ltd., Natalie is studying the interactive effects of maternal stress and rearing enrichment on the performance of Chinook salmon. When she isn’t doing science, Natalie is communicating it; from SEB journal summaries to poems about flatfish. You can find her on Twitter as @phishdoc and at