Kimberly G. Smith

Distribution of Summer Birds Along a Forest Moisture Gradient in an Ozark Watershed

Vegetational and physical habitat factors were measured in 110 0.05-ha circular plots around singing d d of eight bird species in a small watershed in northwestern Arkansas during June and July 1973. Sixty birdless plots were similarly sampled in the driest and most moist areas of the watershed to determine a forest moisture gradient. Principal component analysis of the combined avian community habitat data determined that the forest moisture gradient is important in the distribu- tion of the birds, although multiple analysis of variance showed that no one factor can account for the significant distribution. Principal component analysis of the individual species determined the unique characteristics of the realized niches of each species. An ordination of the species using linear discrim- inant function analysis of the 60 forest samples was similar to the ordination based on the bird distribution, but suggests that other factors are determining the precise distribution of the birds. No species shows a great affinity for the drier forest, although Tufted Titmice seem able to utilize the moist and dry forests equally. The Hooded Warbler, Ovenbird, and Acadian Flycatcher have shorter niche widths than early arriving migrants and permanent residents and can be considered obligatory moist forest species. The results show that the moist forest is of great importance to the avian community and reasons for the lack of birds in the dry forest are discussed.

Emergence of 13‐Yr Periodical Cicadas (Cicadidae: Magicicada): Phenology, Mortality, and Predators Satiation

We examined emergence of male and female 13-yr periodical cicadas (Brood XIX) and mortality, due to avian predation, fungal infection (Massospora cicadina), en? vironmental factors, and senescence. We compared relative contributions of the sources of mortality, and determined the temporal pattern of avian predation associated with predator satiation and mortality. Based on a mean density of 6.65 emergence holes/m2, we estimated that 1 063 300 cicadas emerged on our 16-ha study area in northwestern Arkansas during May 1985. Males appeared first in emergence traps in early May and emerged more synchronously than did females. About 50% of the population emerged during four consecutive nights, and peak abundance of adult cicadas occurred in late May. Based on samples from mortality traps, at least 40% of the population died in severe thunderstorms during the first week of June, demonstrating that stochastic factors can be major influences on periodical cicada populations. Fungal infection was not a major source of mortality. The first cicadas that emerged in early May were eaten by birds, but avian predators became satiated. Birds consumed 15-40% ofthe standing crop at low cicada densities, but very little of the standing crop was consumed when cicada densities were > 24 000 indi- viduals/ha on the study site. Avian predators appeared to be satiated for several weeks, and by the time their foraging activities increased due to demands imposed by feeding young, density of adult cicadas was relatively low. Mortality due to predation gradually increased to near 100% as the density of adult cicadas declined in June. Based on estimates of cicada emergence and deaths due to avian predation where adult cicada activity was greatest, birds consumed only ?15% of the adult cicada population. Therefore, only a small proportion ofthe adult cicada population was actually consumed by avian predators. These results demonstrate that, indeed, the synchronized, explosive emergences of peri? odical cicadas may be classical examples of predator satiation.

An organism-centered approach to some community and ecosystem concepts.

Abstract We present a discussion of the ecological concept of the niche based on the perspective of the individual organism, rather than that of a population or species. This discussion is then expanded to include other related ecological concepts such as guild, environment, habitat and functional group. Using the individual as the focus permits the development of a system of concepts which, we believe, approximate the way that ecological interactions occur in nature.

Deuterium Measurements of Raptor Feathers: Does a Lack of Reproducibility Compromise Geographic Assignment?

Abstract.— Despite the widespread use of stable isotopes in studies of avian movement, key assumptions on which the methodology is based remain unsubstantiated, including the assumption that measurements of stable hydrogen isotopes in feathers (&dgr;Df) are consistent across time within the same laboratory or among laboratories using the same analytical protocols and keratin standards. We tested this assumption by remeasuring &dgr;Df from 211 raptor feathers within and between laboratories. Initial and repeat samples were prepared and analyzed using identical protocols but analyzed in distinct automated runs with laboratory staff blind to sample identity. Reproducibility of &dgr;Df measurements varied significantly and substantially among nine independent sample groups. Feather &dgr;D measurements among sample groups exhibited average isotopic shifts from -15.6%‰ to +27.5%‰ (an absolute difference of 43.1%‰), with standard deviations from 6.0%‰ to 12.4%‰. Therefore, despite existing analytical protocols to address issues of reproducibility, empirical data suggest that comparing &dgr;Df measurements among studies or labs and pooling samples analyzed during different automated runs within a laboratory remain problematic. More importantly, poor reproducibility compromises the geographic assignment of origins based on &dgr;Df , because the substantial differences in &dgr;Df measurements between automated runs can result in spurious inferences regarding the origins of migratory birds. We caution against the continued use of &dgr;Df for predicting geographic origin, and for addressing important conservation questions, until the factors affecting poor reproducibility are identified and improved reproducibility is demonstrated within and among laboratories across time and taxa.

EFFECTS OF INSECTICIDE-INDUCED REDUCTION IN LEPIDOPTERAN LARVAE ON REPRODUCTIVE SUCCESS OF HOODED WARBLERS

We examined the effects of an insecticide-induced reduction of lepidopteran larvae due to spraying of Bacillus thuringiensis to eradicate gypsy moths (Lymantria dispar) on the reproduction of Hooded Warblers (Wilsonia citrina). Treatment plots had two appli- cations of Bacillus in 1994. No Bacillus application occurred in 1995. Reductions in lepidop- teran larvae were demonstrated by pheromone traps and arthropod samples from oak (Quer- cus spp.) foliage. We analyzed the following reproductive parameters: nesting success, num- ber of eggs, number of fledglings, egg mass, mass of nestlings at day 5, growth rates, feeding rates, and prey items brought to nestlings. Of these reproductive parameters, three showed both statistical and biological differences. Nesting success was higher in the control than in the treatment zone in 1995, but not in 1994. Nestling masses at day 5 increased over the duration of the breeding season in the treatment zone but not in the control zone. Differences in feeding rates between treatment and control zones occurred only for small clutches. Over- all, the reduction of lepidopteran larvae due to Bacillus application appeared to have only minimal effects on reproduction in Hooded Warblers. Received 9 September 1996, accepted 8

EFFICACY OF IMMOBILIZING FREE-RANGING ELK WITH TELAZOL® AND XYLAZINE HYDROCHLORIDE USING TRANSMITTER-EQUIPPED DARTS

From January 1999 to April 2002, 14 free-ranging elk were darted with a mixture of Telazol® reconstituted with xylazine hydrochloride (HCl) in a forested habitat in southwestern Oklahoma and north-central Arkansas. Elk were darted from ground blinds, tree stands, or a vehicle at distances of 14–46 m and were recovered 37–274 m from the dart site. Elk were located using radiotelemetry with 3-cc disposable Pneu-dart® transmitter darts. Mean±SD dose of Telazol® and xylazine HCl was 590±192 mg/ml and 276±153 mg/ml, respectively, and mean time to standing after injection of reversal agent was 27 min (range: 1–65 min). The combination of Telazol® and xylazine HCl successfully immobilized free-ranging elk, and transmitter-equipped darts permitted successful location of sedated elk by two people in areas of dense forest cover. The dose required to sedate elk appeared to vary depending on physiology and behavior, but no drug-induced mortality occurred despite the wide variance in the doses administered. We recommend 500 mg Telazol® reconstituted with 300 mg xylazine HCl as an initial dose for a ≥200 kg elk. If needed to achieve full sedation, up to 3 additional ml of the mixture may be administered without adverse effects.

Snowpack and variation in reproductive ecology of a montane ground-nesting passerine, Junco hyemalis

Effects of snow depth and rate of snowmelt on reproduction of a montane groundnesting passerine were examined in a 5-year study of Dark-eyed Juncos Junco hyemalis in northern Utah, USA. Distribution of clutch sizes differed significantly among years. Although most clutches contained four eggs, 3-egg clutches, due primarily to second nestings, were more common during a year of early snowmelt and 5-egg clutches were most common during two years of late snowmelt. Average clutch size was lowest in an early snowmelt year and average clutch size and date at which meadows became snow-free were significantly positively correlated. Average hatching date of 4-egg clutches was also significantly positively correlated with date at which meadows became snow-free demonstrating that most birds tracked the pattern of snowmelt. Early snowmelt may allow more pairs to attempt second nesting, but late-lying snow causes breeding to be delayed, allowing time for only one nesting attempt. During this delay, female juncos continue to feed and some may gain enough reserves to produce larger clutches, accounting for the increase in average clutch size in years of late snowmelt. Three female juncos examined in June 1982, a period of late snowmelt, had significantly more lipid reserves than did six males collected at the same time, suggesting that females are not physiologically stressed while awaiting snowmelt. By tracking snowmelt patterns, juncos synchronize production of young with peak summer insect abundance and potentially decrease risk of predation. Snow depth and rate of snowmelt are thus proximate environmental factors that may influence the reproductive ecology of ground-nesting passerines.

EFFECTS OF TORNADO DAMAGE ON FOREST BIRD POPULATIONS IN THE ARKANSAS OZARKS

Abstract Breeding bird populations were studied in forests recently damaged by tornados and in adjacent undamaged forests in the Ozark National Forest, Arkansas. During 1999 and 2000, surveys were undertaken at 6 points in forest moderately damaged by a tornado in 1996 and at 6 points in nearby undamaged forest. An additional 18 counts, 6 each in undamaged, moderately damaged, and heavily damaged forest, were undertaken in 2000 in an area affected by a 1999 tornado. Typical forest species, such as red-eyed vireo and ovenbird, were significantly less abundant in tornado-damaged forest than in undamaged forests, while edge species, such as indigo bunting and white-eyed vireo, were more abundant in damaged forest than in undamaged forest. Surprisingly, abundances of some species, such as black-and-white warbler, did not differ significantly between damaged and undamaged forests. Species composition differed between heavily damaged forest and moderately damaged or undamaged forest, with a number of species occurring only in the heavily damaged forest type. The congeneric summer tanager and scarlet tanager seemed to show habitat segregation in the study sites, with summer tanagers occurring in tornado-damaged forest and scarlet tanagers occurring in undamaged forest.

Sexual Dimorphism and Foraging Behavior of Emerald Toucanets Aulacorhynchus prasinus in Costa Rica

Foraging behavior and diet of male and female Emerald Toucanets were studied at Monteverde, Costa Rica during both wet and dry seasons to determine if sexual dimorphism in bill morphology was related to differences in feeding behaviors between sexes. Based on analysis of museum specimens, bills of males averaged about 20% longer than those of females and the sexes could be reliably distinguished based on differences in bill morphology. Analysis of foraging sequences as first-order Markov chains revealed no differences between sexes or seasons in relative height, relative position in a plant, or foraging substrate. Regardless of season, both male and female toucanets foraged on twigs in outer portions of the mid-canopy. Seasonal differences existed in foraging height above ground, time spent in a single foraging bout, and distance moved between foraging bouts. However, the only within-season difference between sexes was that an average foraging bout during the dry season was longer for females than for males. Toucanets were observed eating fruits, mostly berries, and flowers from 47 species of plants. Fruits consumed in the wet season were larger and heavier than those consumed in the dry season, but no obvious within-season differences existed between sexes in size, color, or type of fruit consumed. We conclude that sexual dimorphism in bill morphology of Emerald Toucanets is not related to differences in foraging behavior or diet. Because of the nature of the resource, foraging-related sexual dimorphism should be rare in frugivorous birds.

Range Extension of the Blue Jay into Western North America

The Blue Jay (Cyanocitta cristata) is a common permanent resident or migratory summer resident in the eastern half of North America (reviewed by Wenger, 1975). Few extralimital winter records of Blue Jays existed in western North America prior to 1972. Since then, western sightings have been increasing annually with over 220 records in the winter of 1976-77. Because Blue Jays are usually conspicuous, easily identified, and often remain in localized urban areas for several weeks, these reports reflect a genuine increase and suggest that the Blue Jay is rapidly expanding its wintering range. Recent records also indicate a westward expansion of the breeding range. This report reviews the recent changes in the Blue Jays distribution and offers explanations for two important questions concerning this expansion: (1) what factors are influencing this westward expansion, and (2) where is the origin of these pioneering individualsJ