Final Key 2010 - Avian Biology Final Exam Answer Key Spring...

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Avian Biology Final Exam Answer Key Spring 2010 1a) (Doug graded). Advantages of fruit include: they are easy to find because they are brightly colored; they are easy to capture; they are easy to digest; they are often abundant (when you find one, you find many). Disadvantages of fruit include: they are seasonal in their abundance; they are not nutritionally balanced (low in protein); they often have secondary compounds. b) You would expect that territoriality would be more common in the temperate zone, probably when birds were not consuming fruit. This is because fruit is patchily distributed, so poor in nutritional value, and so abundant when found that it typically doesn’t make economic sense to defend a territory to provide access to fruit. Thus, tropical species that eat mostly fruit most of the year are generally not territorial. Temperate birds when nesting rely heavily on insects to provide protein for eggs and young; they are almost always territorial when breeding. c) The small territories of males are most likely territories associated with a lek. (You know that frugivorous birds are often polygynous and that leks mating systems are typically associated with polygynous species and fruit-eating.) The females may protect territories during the breeding season, when they must find a lot of protein (eat a lot of insects) to support egg production and nestling growth. Because they switch to a diet of insects, they switch their behavior to being territorial. When young are independent, the females switch back to a diet of fruit and stop defending territories. 2a) (Doug graded) Seeds. All fruits contain seeds, which are indigestible by fruit-eating birds. The seeds represent ballast (extra weight) which is an expensive cost for a flying animal. b) Most people predicted that fruits near the top of the tree or in the center of the tree would be removed first because in those locations birds were safer from predators. Alternatively, those fruits might also be removed first because they are closer to where birds hang out in the trees (e.g., singing males perch high in the tree) or because they are sweeter (exposed to more sunlight). c) The fruit-eating birds that flock move silently from tree to tree so as not to draw attention to themselves. One in a tree, however, they are more exposed to predators because predators are likely to hang out near fruiting trees – by doing so they can be assured of an assortment of hungry/distracted prey. By being noisy in fruiting trees, the flocking species can attract non-flocking species like manakins into the tree. Doing so reduces risk to the flocking species through the dilution effect and through the “extra eyes” provided by the non-flocking species. Male manakins hang out near fruiting trees but wait for a big flock in a tree before entering it to feed. They are brightly colored and presumably highly vulnerable to predators if they forage by themselves in a fruiting tree. Female manakins, on the other hand are cryptically colored and can quietly feed in fruiting trees without nearly
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Final Key 2010 - Avian Biology Final Exam Answer Key Spring...

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