Browsing by Subject "ornithology"
Now showing 1 - 7 of 7
- Results Per Page
- Sort Options
Item Accelerational Implications of Hummingbird Display Dives(1995-10) Larimer, James L.; Dudley, Robert;Item Assessing the Consequences of Brood Parasitism and Nest Predation On Seasonal Fecundity in Passerine Birds(1995-04) Pease, Craig M.; Grzybowski, Joseph A.; Pease, Craig M.Brood parasites and nest predators reduce the seasonal fecundity and, hence, the population growth rates of their victims. However, most field studies do not measure directly how parasites and predators decrease seasonal fecundity, but instead measure the impact of these organisms on individual nesting attempts. Because a female may renest after losing a nest to predation, abandoning a parasitized nest, or successfully fledging a brood, knowing how brood parasites and nest predators reduce the number of offspring fledged from individual nesting attempts is not equivalent to knowing their impact on seasonal fecundity. We address this problem by developing a mathematical model that: estimates several parameters describing the natural history of this system, including the brood-parasitism rate, nest-predation rate, and probability of nest abandonment in response to a parasitism event; and extrapolates to seasonal fecundity from these parameters and others describing the length of the breeding season, the timing of events in the nesting cycle, and the productivity of parasitized and unparasitized nests. We also show how different researchers using different observational methodologies to study exactly the same population likely would arrive at noticeably different conclusions regarding the intensity of brood parasitism, and we provide mathematical formulas for comparing among several of these measures of parasitism. Our procedures extend Mayfield's method for calculating nest-success rates from nest-history data in that we simultaneously estimate parameters describing nest predation and brood parasitism, predict seasonal fecundity from these parameters, and provide confidence intervals on all parameter estimates. The model should make the design and interpretation of logistically difficult empirical studies more efficient. It also can be specialized to species affected by nest predators but not brood parasites. We use the model to analyze prairie Warbler (Dendroica discolor) and Black-capped Vireo (Vireo atricapillus) nesting data. We estimate the model's parameters for these species and use the resulting estimates to predict seasonal fecundity. For both species, the predicted seasonal fecundity closely matches the value measured directly.Item Clutch Size and Fledging Success in the Turquoise-Browed Motmot(1986-01) Scott, Peter E.; Martin, Robert F.; Scott, Peter E.; Martin, Robert F.Clutches of 4 eggs accounted for 64-73% of all clutches laid in 3 yr by a population of Turquoise-browed Motmots (Eumomota superciliosa) in Yucatan, Mexico. The consistently high frequency of 4-egg clutches was associated with only a slight advantage in fledging success relative to clutches of 3 eggs, which ranged in frequency from 11 % to 33%. Differences in number of young fledged and proportion of hatchlings fledged were not statistically significant over 3 yr or in any particular year. Clutches of 4 yielded more surviving young in 2 of 3 yr, averaging 2.02 compared to 1.71 for clutches of 3. The proportion of hatchlings that fledged was higher in broods of 3 (overall= 0.67) than in broods of 4 (overall= 0.55) in 2 of 3 yr. The proportion of hatchlings fledged from clutches of 5 (0.36) was lower over 3 yr than that fledged from clutches of 4 or 3. Approximately 40% of nestling mortality in nests that escaped predation was due to starvation. Other known causes included falls from nests and parasitism by maggots.Item Facultative Altitudinal Movements by Mountain White-Crowned Sparrows (Zonotrichia Leucophrys Oriantha) in the Sierra Nevada(2004-10) Hahn, Thomas P.; Sockman, Keith W.; Breuner, Creagh W.; Morton, Martin L.; Breuner, Creagh W.Mountain White-crowned Sparrows (Zonotrichia leucophrys oriantha) winter in Mexico and often arrive in the vicinity of their breeding grounds in the Sierra Nevada well before nesting is possible. Arrival at Tioga Pass, California (elevation 3,030 m), usually occurs in early May, but residual winter snow and adverse weather can delay nesting for weeks. We used radiotelemetry to determine whether prebreeding Mountain White-crowned Sparrows engaged in weather-related altitudinal movements during the waiting period between the end of spring migration and onset of breeding during 1995-2001, with a range of residual winter snowpacks. Interannual variation in arrival date and onset of egg laying was 18 and 41 days, respectively. We tracked females for two years and males for all seven years. During spring snowstorms (which occurred in four years), radiomarked individuals moved to lower elevation sites, where they often remained for several days. Departing birds left Tioga Pass by early afternoon and returned early in the morning after storms. More frequent storms during tracking increased the likelihood of facultative altitudinal movements, but heavier residual winter snowpack did not. Warm days increased the likelihood of birds returning to Tioga Pass from low elevation. This study demonstrates that facultative altitudinal movement behavior can be a common feature of spring arrival biology in montane-breeding birds. Received 1 November 2002, accepted 30 June 2004.Item A Falconid from the Late Miocene of Northwestern China Yields Further Evidence of Transition In Late Neogene Steppe Communities(2014-07) Li, Zhiheng H.; Zhou, Zhonghe H.; Deng, Tao; Li, Qiang; Clarke, Julia A.; Li, Zhiheng H.; Clarke, Julia A.Although the family Falconidae, which includes extant falcons and caracaras, has a long evolutionary history, most previously reported fossils referred to this family are isolated single elements. We report a new species, Falco hezhengensis sp. nov., represented by a nearly complete and articulated skeleton from the Late Miocene deposits of Linxia Basin in northwestern China. The new fossil shares an array of derived morphologies with the genus Falco, and analysis of the largest morphological dataset for Falconidae, sampling most genera, identifies the specimen as a new stem kestrel. The phylogeny shows a high degree of congruence with published molecular phylogenies and time trees supporting a Miocene radiation of Falconidae. The species provides a new calibration for the divergence of extant kestrels from other Falco. Remains of a small mammal, a jerboa (Dipodidae), are preserved in the abdominal region of the specimen. Integrated with data from other avian remains from the Linxia Basin, the new fossil provides further support for changes in the open steppe environment of Central Asia since the Late Miocene. Changes in falconid ecology and diet, shifts in small-mammal abundances, as well as the extinction of the Central Asian ostrich may be involved in community turnover in the Late Neogene.Item Red-Eyed Vireos Have Difficulty Recognizing Individual Neighbors Songs(1993-10) Godard, Renee; Godard, ReneeI investigated recognition of individual neighbors' songs in a migratory species with large repertoires, the Red-eyed Vireo (Vireo olivaceous). To test for abilities to recognize individual neighbors, I measured responses to playbacks of neighbors' songs from appropriate and inappropriate boundaries in two different years. Because the responses to the two types of playbacks were not statistically different in either year, I concluded that Red-eyed Vireos have difficulty recognizing their neighbors by song. If recognition of neighbors serves to reduce energy expended in territorial defense during the breeding season, a large repertoire could be costly to male Red-eyed Vireos.Item Rhetoric Vs. Reality: A Commentary an "Bird Origins Anew" by A. Feduccia(2015-04) Smith, N. Adam; Chiappe, Luis M.; Clarke, Julia A.; Edwards, Scott V.; Nesbitt, Sterling J.; Norell, Mark A.; Stidham, Thomas A.; Turner, Alan; van Tuinen, Marcel; Vinther, Jakob; Xu, Xing; Clarke, Julia A.Birds are maniraptoran theropod dinosaurs. The evidence supporting the systematic position of Avialae as a derived clade within Dinosauria is voluminous and derived from multiple independent lines of evidence. In contrast, a paucity of selectively chosen data weakly support, at best, alternative proposals regarding the origin of birds and feathers. Opponents of the theory that birds are dinosaurs have frequently based their criticisms on unorthodox interpretations of paleontological data and misrepresentation of phylogenetic systematic methods. Moreover, arguments against the nested position of Avialae in Dinosauria have often conflated the logically distinct questions of avian origins, the evolution of flight, and the phylogenetic distribution of feathers. Motivated by a Perspectives article with numerous factual inaccuracies that recently appeared in The Auk, we provide a review of the full complement of facts pertaining to the avian origins debate and address the misplaced criticisms raised in that opinion paper.