Time versus energy minimization migration strategy varies with body size and season in long-distance migratory shorebirds

• Main Authors: M Zhao, M Christie, J Coleman, C Hassell, K Gosbell, S Lisovski, C Minton, Marcel Klaassen
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: 2017
• Subjects: Ecology not elsewhere classified; Evolutionary biology not elsewhere classified; Environmental management not elsewhere classified; Science & Technology; Life Sciences & Biomedicine; Ecology; Environmental Sciences & Ecology; Optimal migration theory; Migration strategy; Time minimization; Energy minimization; Light level geolocator; Migration speed; Body size; CURLEWS NUMENIUS-MADAGASCARIENSIS; KNOTS CALIDRIS-CANUTUS; FOOD AVAILABILITY; FUEL DEPOSITION; AVIAN MIGRATION; ANNUAL CYCLE; SPEED; FLIGHT; BIRDS; PATTERNS; Energy-minimization; Light-level geolocator; Time-minimization; School of Life and Environmental Sciences; Centre for Integrative Ecology; 3103 Ecology; 3104 Evolutionary biology; Calidris canutus
• Online Access: http://hdl.handle.net/10536/DRO/DU:30105510; https://figshare.com/articles/journal_contribution/Time_versus_energy_minimization_migration_strategy_varies_with_body_size_and_season_in_long-distance_migratory_shorebirds/20823349

Background: Migrants have been hypothesised to use different migration strategies between seasons: a time-minimization strategy during their pre-breeding migration towards the breeding grounds and an energy-minimization strategy during their post-breeding migration towards the wintering grounds. Besides season, we propose body size as a key factor in shaping migratory behaviour. Specifically, given that body size is expected to correlate negatively with maximum migration speed and that large birds tend to use more time to complete their annual life-history events (such as moult, breeding and migration), we hypothesise that large-sized species are time stressed all year round. Consequently, large birds are not only likely to adopt a time-minimization strategy during pre-breeding migration, but also during post-breeding migration, to guarantee a timely arrival at both the non-breeding (i.e. wintering) and breeding grounds. Methods: We tested this idea using individual tracks across six long-distance migratory shorebird species (family Scolopacidae) along the East Asian-Australasian Flyway varying in size from 50 g to 750 g lean body mass. Migration performance was compared between pre- and post-breeding migration using four quantifiable migratory behaviours that serve to distinguish between a time- and energy-minimization strategy, including migration speed, number of staging sites, total migration distance and step length from one site to the next. Results: During pre- and post-breeding migration, the shorebirds generally covered similar distances, but they tended to migrate faster, used fewer staging sites, and tended to use longer step lengths during pre-breeding migration. These seasonal differences are consistent with the prediction that a time-minimization strategy is used during pre-breeding migration, whereas an energy-minimization strategy is used during post-breeding migration. However, there was also a tendency for the seasonal difference in migration speed to progressively disappear with an increase in ...