Body-Fat Levels and Annual Return in Migrating Semipalmated Sandpipers

• Published in: The Auk Vol. 115; no. 4; pp. 904 - 915
• Main Authors: Charles Pfister, Mark J. Kasprzyk, Harrington, Brian A.
• Format: Journal Article
• Language: English
• Published: Lawrence, KS The American Ornithologists' Union 01-10-1998; Ornithological Societies North America; American Ornithological Society
• Subjects: Aerial locomotion; Animal and plant ecology; Animal migration; Animal migration behavior; Animal, plant and microbial ecology; Animals; Aquatic birds; Autoecology; Aves; Biological and medical sciences; Birds; Body fat; Breeding; Calidris pusilla; Foraging; Fundamental and applied biological sciences. Psychology; Length of stay; Marine; Mortality; Ornithology; Sandpipers; Seasonal migration; Vertebrata; United States; North America; Massachusetts; America; A, Atlantic; Stopover site; Long distance; Environmental factor; Lipids; Limicolous; Animal migration; Survival; Body composition; Feed conversion efficiency; Vertebrata; Migratory; Aves; Calidris pusilla; Metabolic storage
• ISSN: 0004-8038; 1938-4254; 2732-4613
• DOI: 10.2307/4089509

Rapid deposition of body fat in preparation for long-distance migration is assumed to be one of the crucial activities of shorebirds at migration staging areas. We tested the hypothesis that annual return rate of Semipalmated Sandpipers (Calidris pusilla) to a migration stopover site is related to fat levels at the time of migratory departure for a long flight over the Atlantic Ocean. Length of stay of color-marked individuals was used to estimate fat levels at departure based on a relationship established at the study site between length of stay and the increase in estimated levels of body fat. Our results support the hypothesis that fat levels at migratory departure are related to the annual return rate and also to annual survival. Individuals remaining long enough to accumulate excess body fat (i.e. the low-risk group) were nearly twice as likely to return as were those below theoretically sufficient fat levels (the high-risk group). Fat levels attained at departure may be an important factor in surviving a long migration flight. However, the fact that some individuals in the high-risk group returned (approximately 25% of individuals in two years) indicates that flight-range formulas may understimate flight capabilities. In the first year of the study 45%, and in the second year 32%, of individuals remained longer than necessary to accumulate theoretically sufficient fat levels, suggesting that some individuals were not operating on a time-selected migration schedule. Disturbance of shorebirds at staging areas may increase the mortality of these birds.