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Migration00:53

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Migration is long-range, seasonal movement from one region or habitat to another. This common strategy, carried out by many different organisms around the world, is an adaptive response that typically corresponds to changes in an organism’s environment, like resource availability or climate. Migrations can involve huge groups of thousands of animals as well as single individuals traveling alone and can range from thousands of kilometers to just a few hundred meters.
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Visually Sexing Loggerhead Shrike Lanius Ludovicianus Using Plumage Coloration and Pattern
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Size differences in migrant sandpiper flocks: ghosts in ephemeral guilds.

Jan L Eldridge1, Douglas H Johnson2

  • 1Department of Ecology and Behavioral Biology, Bell Museum of Natural History, University of Minnesota, 10 Church Street S.E., 55455, Minneapolis, MN, USA.

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|March 18, 2017
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Summary

Ephemeral sandpiper flocks in North Dakota showed random species mixing from a nonrandom pool. Bill length differences suggest size-related selection, like competition, influenced migration corridor use.

Keywords:
CompetitionMigrationNull modelsShorebirdsSize ratio

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Area of Science:

  • Ornithology
  • Ecology
  • Behavioral Ecology

Background:

  • Mixed-species foraging flocks are common among shorebirds during migration.
  • Understanding flock composition can reveal ecological and evolutionary pressures.

Purpose of the Study:

  • To analyze the species composition and bill length distributions of mixed-species sandpiper flocks during spring migration in North Dakota.
  • To compare observed flock compositions with random assemblages from various regional and global species pools.
  • To investigate potential size-related selection pressures influencing sandpiper migration patterns.

Main Methods:

  • Field observations of sandpiper flocks in North Dakota from 1980-1984.
  • Statistical comparison of observed species composition with computer-generated flocks from global, Western Hemisphere, and North Dakota regional pools.
  • Analysis of bill length ratios within mixed-species foraging flocks.

Main Results:

  • Common sandpiper species in mixed flocks exhibited bill length differences of 20-30% (1.2:1 to 1.3:1 ratios).
  • Observed flocks were random mixes of species present in the North Dakota migration corridor.
  • The species pool migrating through North Dakota was not a random selection from broader global or Western Hemisphere pools.

Conclusions:

  • Mixed-species sandpiper flocks in North Dakota represent random associations from a nonrandomly selected migratory species pool.
  • Bill length distributions suggest that size-related factors, potentially interspecific competition, influence sandpiper utilization of this migration corridor.