4B: The Pheasant Case: Handout Case Three Ring-Necked Pheasants As you can see, the male ring-necked pheasant is brightly colored. The white ring at the base of the red and green head stand out against the dull, brownish colors of the fields in which they live. The female, on the other hand, appears well camouflaged in this habitat. Case materials: Problem statement (this page) Pictures of male and female pheasants Information on habitat, feeding, and mortality Predation information Descriptions of breeding habits graph of male reproductive success Phylogenetic tree of pheasants Case assignment As with the previous cases, your primary goal is to explain the trait in question from a Darwinian perspective. However, in this case the final product will be a research grant proposal which will have two parts. Part 1: Part 2: Develop a Darwinian explanation that fully accounts for the bright coloration of male pheasants. Integrate into your explanation the evidence you have drawn from the case materials to support your claims. Identify one area of your explanation for which you would want more data. In other words, what key aspect of your explanation were you least confident about? Explain what kind of data would help you resolve that issue and give a detailed description of how you would go about collecting that data. Remember: this is a competition so you need to provide compelling reasons for the research program you are proposing.
Miscellaneous Pheasant Information Habitat: The ring-necked pheasant largely inhabits grassland areas at the edge of stands of trees or hedges. The presence of dense grasses appears to be an important habitat attribute. Female birds often situate their nests in cover that provides partial to complete overhead concealment. (See pictures provided.) Feeding Behavior: All pheasants are largely vegetarian, and the majority are adapted to seed eating. Individual birds often have definite preferences for particular types of food. Evidently such individuals form preferences for foods on the basis of form and color, perhaps with the aid of tactile (touch) impressions, but with taste differences evidently of little significance. During the first few weeks of life pheasants consume a high incidence of insects. By the time the birds are adult, however, over 90 percent of the food intake comes from plant sources. Mortality Rates: Determination of the overall mortality rates of any animal species is a complex process, since it is dependent upon a large number of variables that are not only difficult to measure but also may vary from year to year or from place to place. In the North American ring-necked pheasant population the average estimated female adult mortality rate is 66 percent. Male mortality rates of pheasants average considerably higher than this. It is believed that relatively few males are necessary in the population to maintain fertility among females. Data from Denmark also suggest that the male pheasants suffer a considerably higher mortality rate of approximately 78 percent annually, as compared to a female annual mortality rate of about 62 percent.
Pheasant Predation The role of predation is extremely difficult to determine in influencing bird distribution and abundance. One study tracked birds using radio transmitters and found that among 105 deaths of such birds, 80 percent of the total were attributed to predation. Of these 76 deaths, 46 were believed to be the result of mammalian predation, 19 caused by birds, and 11 of undetermined cause. It is believed that foxes are responsible for the majority of mammalian predation cases, while smaller numbers were considered to result from cats, minks, dogs, and weasels. Among the bird predators, the most significant source of mortality is due to both the great horned owl and the red-tailed hawk. The table below lists the major pheasant predators, the majority of which detect their prey by sight during daylight hours. Results of stomach analysis Percentage of predators having pheasant remains present Mammals Red fox 8.9 Grey fox 4.0 Raptors Great horned owl 18.1 Red-tailed hawk 10.5 Cooper s hawk 5.3 Northern harrier - Pheasant Courtship Courtship season for pheasants is a noisy and colorful time of year. It occurs in early spring and typically lasts for several weeks. During this time male pheasants show increased aggression toward one another and distribute themselves throughout the habitat range into relatively small territories within which they remain for the duration of the courtship season. During this time females move freely within the entire habitat range and encounter many males. Sexually mature males, upon seeing a female, will begin a series of mating displays. Tow characteristics of the male mating display are called waltzing and wing-flapping. In the waltzing display the male presents on wing by lowering it as he advances past or around his partner. The wing-flapping courtship display involves the male holding the head and body in a vertical position while noisily flapping his wings in short repeated bursts. If the female is receptive to mating with a male she will assume a crouched posture as the male displays. Females only respond to a small fraction of male courtship displays. During the courtship season females generally spend more time in the territories of males with bright plumage than in the territories of males with less brightly colored plumage (including juvenile males). Nearly all mature females mate during every breeding season. On the other hand, only a fraction of the males will successfully mate during a particular year.
Pheasant wing flapping display.
Pheasant Reproductive Biology Graph Distribution of Male Reproductive Success 0 Number of Offspring Produced 1-5 5-10 10-15 1 15-20 20-30 Series7 Series6 Series5 Series4 Series3 Series2 Series1 30+ 0 5 10 15 20 25 Number of Males
Phylogenetic Data As the branching diagram below shows, pheasants are closely related to partridges, quail, and grouse. The table shows how various characters differ between these groups of birds. Grouse Quail Partridge Pheasant Lower Jaw smooth toothed smooth smooth male mating strategy differences between sexes average clutch size waltzing display many mates single mate single mate many mates pronounced slight slight pronounced 5-12 10-15 4-16 1-12 no no yes yes