Tropical Bird Wallpaper Biography
Perhaps the most ingenious experiment on avian badges involved the European Great Tit, a close relative of North American chickadees and titmice (all are members of the same genus, Parus). This species has a dark cap, white cheeks, and a dark breast stripe/bib. Torbiorn Järvi and Marten Bakken of Norway's University of Trondheim used radio-controlled motorized stuffed birds at a feeder to test the efficacy of the breast stripe as a badge. When a Great Tit approached the feeder, the stuffed bird could be rotated to face the incoming individual and to perform a "head-up" aggressive display. When, and only when, the stuffed bird had a breast stripe wider than that of the incoming bird was the latter frightened away.
Evidently badges can signal status in avian societies -- but this presents evolutionists with a considerable mystery. Since they are arbitrary symbols, why isn't cheating widespread? Why don't first-year Harris' Sparrows grow dark plumage just like adults? Why don't weakling Great Tits develop broad breast stripes and monopolize the food at feeders? Badge systems seem to have built into them the seeds of their own evolutionary destruction, since frequent cheating should soon make all the signals ambiguous.
One way out of this seeming dilemma has been suggested. Perhaps dominance in monogamous birds (as opposed to polygynous ones, where dominant males may get many more matings) does not in itself confer a selective advantage. Subordinate birds may not get access to the best resources, but they also may not have to expend much energy defending what they've got. Being subordinate may be just as good an evolutionary strategy as being dominant -- both kinds of individual may be equally successful reproductively. If that is the case, there would be no advantage to cheating, and one would not expect such behavior to evolve
Perhaps the most ingenious experiment on avian badges involved the European Great Tit, a close relative of North American chickadees and titmice (all are members of the same genus, Parus). This species has a dark cap, white cheeks, and a dark breast stripe/bib. Torbiorn Järvi and Marten Bakken of Norway's University of Trondheim used radio-controlled motorized stuffed birds at a feeder to test the efficacy of the breast stripe as a badge. When a Great Tit approached the feeder, the stuffed bird could be rotated to face the incoming individual and to perform a "head-up" aggressive display. When, and only when, the stuffed bird had a breast stripe wider than that of the incoming bird was the latter frightened away.
Evidently badges can signal status in avian societies -- but this presents evolutionists with a considerable mystery. Since they are arbitrary symbols, why isn't cheating widespread? Why don't first-year Harris' Sparrows grow dark plumage just like adults? Why don't weakling Great Tits develop broad breast stripes and monopolize the food at feeders? Badge systems seem to have built into them the seeds of their own evolutionary destruction, since frequent cheating should soon make all the signals ambiguous.
One way out of this seeming dilemma has been suggested. Perhaps dominance in monogamous birds (as opposed to polygynous ones, where dominant males may get many more matings) does not in itself confer a selective advantage. Subordinate birds may not get access to the best resources, but they also may not have to expend much energy defending what they've got. Being subordinate may be just as good an evolutionary strategy as being dominant -- both kinds of individual may be equally successful reproductively. If that is the case, there would be no advantage to cheating, and one would not expect such behavior to evolve
Tropical Bird Wallpaper
Tropical Bird Wallpaper
Tropical Bird Wallpaper
Tropical Bird Wallpaper
Tropical Bird Wallpaper
Tropical Bird Wallpaper
Tropical Bird Wallpaper
Tropical Bird Wallpaper
TROPICAL BIRDS
Tropical Bird Flying & Other Tropical Birds
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