Doctor of Philosophy / Department of Biology / Brett K. Sandercock / Sexual selection via female choice and male-male aggression leads to elaboration of male traits. If male traits correlated with reproductive success are honest signals of male quality, survival costs may be associated with the expression of those traits. Testosterone (hereafter ‘T’) may enhance male breeding success, but T can also reduce immunocompetence and survival. Socially monogamous male birds with higher circulating T experience reproductive advantages, but the role of T in lek mating systems is largely unknown. To address these issues, I individually marked and conducted focal behavioral observations of greater prairie-chickens (Tympanuchus cupido) at five lek sites over a 5-year period. Females were fitted with radio-telemetry to monitor nesting success and survival. I examined the relationship between male traits and mating success using multinomial discrete choice models, a statistical method not previously applied to studies of sexual selection. Male mating success was highly skewed at greater prairie-chicken leks with 18.5% of males obtaining 87.2% of all successful copulations (n = 108 males; 85 copulations). Mating success was influenced most by male behavior, followed by several morphological attributes. The role of T was quantified using blood samples and by experimentally implanting a subset of males with T. T did not consistently affect mating success. Non-territorial males had lower T levels than territorial males. Among territory holders, T was unexpectedly negatively correlated with mating success. However, the odds of receiving a copulation were 4.3 times (0.42 to 45.3) greater for T-implanted males than males with sham implants. Future work should explore the interactions among the immune system, parasite load, and mating success of prairie-chickens. Annual survival of male prairie-chickens was not related to mating success, behavior, age or T level, suggesting there is no cost of increased male mating success. Like males, reproductive success of females was also highly skewed because < 10% of nests successfully hatched young. Comparisons of seasonal and annual survival rates indicate that females experience increased mortality during the breeding season relative to the nonbreeding season. Synthesis of field estimates of demographic parameters indicates prairie-chicken populations will decline without changes in rangeland management to reduce predator numbers or provide more nesting cover.

The epaulets of male Red-winged Blackbirds (Agelaius phoeniceus) are frequently cited as a sexually selected plumage ornament, but a number of laboratory and field studies provide little evidence that they are currently experiencing sexual selection. We used hair dye to dull epaulets of free-living territorial males prior to pair formation to determine if manipulated males experienced disadvantages in comparison with control males. We found no differences between control males and males with dulled epaulets in territorial behavior (territory size, song rate, trespass rate, and loss of territory), paternal care (time spent on territory and in antipredator sentinel behavior, and response to a model crow to simulate the threat of predation), pairing success (number of social mates), apparent reproductive success (numbers of nesting attempts, eggs/nest, nestlings/egg, and fledglings/nestling), or realized reproductive success (numbers of within-pair, extra-pair, and total fledglings as determined by DNA fingerprinting). We then used a meta-analysis of 11 published studies of Red-winged Blackbirds to determine if there is an overall effect of epaulet color or size on male-male competition, female choice, or reproductive success. Our results show that epaulet size has a small positive effect on male reproductive success, but epaulet color has no effect on male-male competition, female choice, and male reproductive success. One explanation for the seeming contradiction between studies that show that epaulets are necessary for territory defense and those that conclude that epaulets are not currently under selection is that epaulets serve as one of several cues of species recognition, especially among males at close range. An alternative explanation proposes counter-balancing intersexual advantages and intrasexual disadvantages of epaulet expression. Additional studies are needed to test these alternatives.

Reproductive success of white-faced ibis (Plegadis chihi) was measured in nine colonies on marshes in northern Utah during 1979. The effects of pesticides and characteristics of colonies and sub-colonies on reproductive success were examined. DDE was present in all 80 eggs sampled and had a geometric mean concentration of 1.25 ppm. Shell thickness of 176 eggs was 4.3 percent below pre-1945 thickness. Shell thickness was weakly correlated with residues of DDT, DDE, Dieldrin, and heptachlor epoxide. Residues of these four pesticides were all correlated with each other. However, because of the stronger correlations between shell thickness and two residues, DDE and DDT, and because of studies in the literature, it was concluded that these two residues were responsible for the observed shell thinning. Observed levels of pesticides did not cause sufficient shell thinning to reduce hatching success, but clutch size was negatively correlated with pesticide residues. Only two characteristics of colonies were observed to be associated with differences in reproductive success. Earlier sub-colonies had larger clutches and larger colonies suffered higher rates of predation. If there are effects of subcolony size, degree of nesting synchrony, vegetation type, or avian species association on reproductive success, they may not be detectable with one year of data.

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第20636号 / 農博第2243号 / 新制||農||1053(附属図書館) / 学位論文||H29||N5080(農学部図書室) / 京都大学大学院農学研究科地域環境科学専攻 / (主査)教授 北山 兼弘, 教授 田中 千尋, 教授 松浦 健二 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第21334号 / 理博第4430号 / 新制||理||1636(附属図書館) / 京都大学大学院理学研究科生物科学専攻 / (主査)教授 古市 剛史, 教授 湯本 貴和, 教授 髙井 正成 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

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The reproductive success of the Purple Martin is dependent upon many factors. This study measured reproductive success of the Purple Martin (Progne subis subis) based on parental age and type of housing used. Reproductive parental ages consist of adults (experienced breeders) and subadults (first time breeders). Housing types included in this study were aluminum housing, wooden housing, plastic gourds, natural gourds, SuperGourds, and mailbox housing. The reproductive success was defined as the percentage of the original clutch that fledged. Study sites were located in Alabama, Indiana, North Carolina, Oklahoma, Tennessee, and Virginia. Pairs mating nonassortatively by age group had lower reproductive success than adults and subadults that were paired assortatively. Purple Martins were the most reproductively successful in SuperGourds and the least reproductively successful in wooden housing. This study provides evidence that may be basis for further research, help support the conservation of the Purple Martin, and aid reproductive success on its breeding grounds.

Marine turtle reproductive success is strongly correlated with the stability and quality of the nesting environment. Because females show fidelity to key nesting beaches, the management and physical characteristics of these beaches directly affect future generations of marine turtles and may be essential for the recovery of these threatened and endangered species. The impacts of beach restoration on loggerhead turtles (Caretta caretta) and on green turtles (Chelonia mydas) were investigated. Previous studies concerning beach nourishment projects have focused on loggerhead turtles. I compared data between nourished and non-nourished areas and between loggerhead and green turtles. I found, at one season post-nourishment, negative effects on nesting success and no significant effect on reproductive success for both loggerheads and established the same relationships with green turtles. Physical attributes of the fill sand, which did not facilitate acute scarp formation or severe compaction, did not physically impede turtles in their attempts to nest. Instead, the decrease in nesting success was attributed to an absence of abiotic and or biotic factors that cue nesting behavior. The increase in loggerhead nesting success rates during the second season post-nourishment was attributed to the equilibration process of the seaward crest of the berm. After the beach was restored, both species of turtles placed nests significantly farther from the water in the nourished area than in the non-nourished area. Green turtles nested on or near the dune and loggerheads nested on the seaward crest of the berm. The tendency of loggerheads to nest closer to the water resulted in more loggerhead than green turtle nests being "washed out" by erosion during the equilibration process. There was a significant increase in hatching success only for loggerheads when wash outs were excluded, thus illustrating the importance of nest placement and the detrimental effects of the equilibration process to the reproductive success of loggerheads. A decrease in reproductive output occurred during the first season post-nourishment. The reduction in the estimated total number of hatchlings produced (reproductive output) was a consequence of decreased nesting success lowering nest numbers. This reduction demonstrates that, regardless of similar reproductive success rates, marine turtles incurred net losses during the first season following nourishment. These results further reveal the impacts of decreased nesting success and the importance of minimizing excessive non-nesting emergences associated with beach nourishment.

Vertebrate males frequently carry higher numbers of parasites than females. This bias in parasite loads could be a consequence of sexual selection. Grouping species are also assumed to be afflicted with larger numbers of parasites than solitary animals and associated costs of this parasitism could vary with group size or structure. I examined sex-biased parasitism and the influence of group size on parasite loads in Cape ground squirrels (Xerus inauris), a highly social species that occurs in the arid regions of southern Africa. Males carried three times as many ectoparasites as females, but females harbored nearly three times more endoparasites than males. Amount of time spent (per hour) autogrooming was similar between males and females, but amount time spent allogrooming by adult female was over eleven times that of adult males. Longer allogrooming of group members could be decreasing the numbers of ectoparasites of group members and ultimately the group. Males infrequently give or receive allogrooming and travel in very large home ranges, potentially increasing their exposure to ectoparasites. However, movement throughout a large home range may result in males foraging in areas with lower densities of fecal pellets, which could explain the lower endoparasite loads observed in males. When I considered the age class of group members, female age classes were similarly parasitized but male age classes were not. Sub-adult males carried similar ectoparasite loads to adult males and similar endoparasite loads to adult females. This result is of particular interest because sub-adult males are becoming scrotal but typically remain in the group until adulthood. Sexual selection does appear to influence parasite loads in this species, and parasite removal or avoidance potentially mitigates individual parasite loads and their associated costs. Parasites can be detrimental to the health, longevity, and reproduction of their hosts, but these costs are rarely quantified. I removed ectoparasites and endoparasites from Cape ground squirrels for three months and evaluated changes in female body mass, reproduction, burrow use, and grooming in response to parasite removal. Female body mass did not increase with parasite removal, but reproductive success (per capita offspring raised to emergence) increased nearly four-fold, while allogrooming by treated females decreased. Since breeding is highest in the late winter dry season when fewer resources are available, the impact of parasites may be highest during this season. Lactation and gestation are the most physiological stressful processes that females undergo, and the dramatic increase in reproductive success in treated females suggests that these females are able to allocate more resources to reproduction than females afflicted with parasites. These results suggest that studies investigating reproduction and fecundity must consider the vulnerability of the host to parasite infection and the potential impact on reproductive success.