Visual Communication in Birds

Visual Communication in Birds

  • Plumage Color Patterns

    • Concealment:
    • Cryptic Coloration: Camouflage that allows birds to blend with their environment.
      • Example: Common nighthawk.
    • Disruptive Pattern: Bold color patterns that break up the outline of the bird to confuse predators.
      • Example: Killdeer at Bosque del Apache NWR.
    • Countershading: Darker color on the back and lighter color on the underside; reduces shadow appearance and outlines.
      • Example: Spotted sandpiper.
    • Reverse Counter-shading: Lighter color on top with a darker underside, making birds more conspicuous.
      • Example: Black-bellied plover.

  • Species Recognition

    • Distinctive plumage and coloration aid in distinguishing different species.
    • Genetic differences influence coloration, affecting mate selection.
    • Example: Snow geese which exist in white and blue phases; geese tend to mate with individuals of the same color phase influenced by early imprinting.

  • Individual Recognition

    • Birds recognize mates, neighbors, and new individuals through variations in plumage, size, vocalizations, and behavior.
    • Example: Scissor-tailed flycatcher.

Displays in Communication

  • Displays: Specialized behaviors conveying information between sender and receiver, often linked to evolutionary history.

    • Example: Great blue heron displays include various postures and movements such as stretch, forward display, and wing preen.

  • Contexts and Messages of Displays:

    • Various displays serve multiple purposes including external disturbances, nest defense, and male advertisement.
    • Displays convey identification, intents of locomotion, attack, and even social bonding.

Ritualization and Agonistic Behavior

  • Ritualization: Evolution of signals from non-signal movements like feeding into courtship displays (e.g., tidbitting).

  • Graded Displays: Show varying intensities of motivation.

    • Example: Stellar’s jay where higher crest indicates greater aggression.

  • Agonistic Behavior: Encounters that are aggressive, often avoided to minimize injury.

    • Use of Threat Displays (indicating readiness to attack) and Appeasement Displays (indicating a desire to avoid attack) to manage confrontations.

Sexual Selection

  • Sexual Dimorphism: Differences in size and color between sexes often due to mate competition and female preference.

  • Two primary modes of sexual selection:

    • Male-Male Competition: Example of red-winged blackbirds where males with better territories attract more females.
    • Female Choice: Example: Long-tailed widowbirds demonstrate preference for males with longer tails, impacting mating success.

  • Extrinsic Displays: Displays not reliant solely on one's appearance; transferred onto objects.

    • Example: Bowerbirds create elaborate structures to attract females.

  • Good Genes Hypothesis: Females may prefer ornamented males as it may reflect their health; elaborate traits acting as handicap but indicating genetic fitness.

    • Example: Red jungle fowl with larger combs preferred by females, as they indicate better health and lower parasite burdens.