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Members of the Artemisia tridentata complex (ASTERACEAE; Anthemideae: Artemisia subgen. Tridentatae) have adapted to changing environmental conditions through geographic migration, introgression, and hybridization. These processes have resulted in morphologic and genetic variation. A presumed hybrid (“Bonneville” big sagebrush) of the complex occurs in the moister ranges of A. t. ssp. wyomingensis and can be found growing with shrub species commonly associated with A.t. ssp. vaseyana. These populations appear to be preferred habitat for sage-grouse and are more heavily grazed by ungulates than the parental populations. We determined ploidy levels and conducted a detailed morphological analysis to determine if “Bonneville” is a hybrid entity. Sixteen populations (12 in Oneida Co., ID, and 4 in Rich Co., UT) were selected for the study, representing the putative hybrid (Taxon B) and the putative parents— A.t. ssp. vaseyana (2n = 18), A.t. ssp. wyomingensis (2n = 36), and A.t. ssp. tridentata (2n = 36). Each population consisted of 25 randomly selected individuals for a total of 400 samples. Our analysis showed 3 populations with morphological and chemical characteristics indicating introgression of A.t. ssp. wyomingensis with populations containing A.t. ssp. vaseyana. Based on these results, we designate the Bonneville sagebrush with formal hybrid status of nothotaxon: Artemisia tridentata ssp. × bonnevillensis H. Garrison, L. Shultz, and E.D. McArthur [pro subsp.], 2n = 36.
The distribution and abundance of game fish populations are commonly monitored closely, whereas sampling of nongame species is often neglected. We used a broad-scale salmonid sampling project both to simultaneously assess the distribution and relative abundance of nongame fish species in small streams (i.e., ≤15 m wetted width) in the Snake River basin of southern Idaho and to relate the distribution and abundance of nongame species to abiotic and biotic stream conditions in the study area. Of the 1738 reaches surveyed, 34% were dry or contained too little water to support fish, and an additional 21% had flowing water but were still absent of fish. At least one species of nongame fish was captured at 30% of the reaches surveyed, and all 18 native nongame fish species believed present in study area streams were captured. The most widely distributed species was speckled dace Rhinichthys osculus (present in 21% of surveyed reaches, excluding dry and nearly dry reaches), followed by bridgelip sucker Catostomus columbianus (19%), Paiute sculpin Cottus beldingi (15%), and redside shiner Richardsonius balteatus (13%). The species least often present (≤ 1%) were leopard dace Rhinichthys falcatus and peamouth Mylocheilus caurinus. Common carp Cyprinus carpio (captured at 3 locations) and oriental weatherfish Misgurnus anguillicaudatus (2 locations) were the only nonnative nongame species encountered. Catostomids and cyprinids generally formed a composite fish assemblage that was associated with higher stream order (i.e., farther from headwaters), lower elevation, and lower-gradient reaches where streams were wider and deeper. Stream order was the strongest loading factor for canonical correlations constructed for study reaches both above and below Shoshone Falls, suggesting that the increased abundance of catostomids and cyprinids generally occurred on a longitudinal downstream gradient. Biologists sampling game fish populations in streams should also record data on nongame species to more closely monitor their status through time.
We examined parental provisioning behavior of 2 grassland obligate birds, Bobolink (Dolichonyx oryzivorus) and Grasshopper Sparrow (Ammodramus savannarum) in south central Nebraska. We assessed rates of food delivery (provisions * nestling_1h_1) and prey composition by using video recordings. We estimated arthropod availability from sweep net samples collected during 2 breeding seasons. We evaluated the effects of provisioning rate and prey composition on nestling quality inferred through nestling mass. We focused our efforts on lepidopteran larvae and orthopterans, as these orders comprised the bulk of identified prey deliveries. Total provisioning rates at 53 Bobolink nests and 32 Grasshopper Sparrow nests did not predict nestling mass for either species in either year. In one of 2 years, we observed a positive relationship between unidentified prey items and Bobolink nestling mass and a negative relationship between percentage of lepidopteran larvae and Bobolink nestling mass. These observed relationships are likely spurious, however. Parents of both species provided lepidopteran larvae at higher rates than were expected based on availability, and this particular result highlights the potential importance of dietary content to developing nestlings.
This study investigated influences of flow regulation of the Dolores River, Colorado, by McPhee Dam on establishment of 3 native riparian tree species (Populus angustifolia, Populus deltoides subsp. wislizenii, and Acer negundo). Tree establishment was documented with dendrochronology at 2 reference sites, the unregulated Upper Dolores and San Miguel rivers, and at multiple reaches along the Lower Dolores River for a pre-dam, canal-diverted period (1961–1984) and a post-dam period (1985–2008). Tree establishment along the Lower Dolores River relative to unregulated reference rivers was negatively affected by river regulation for A. negundo, but not for P. angustifolia and P. deltoides. For P. angustifolia, similar establishment occurred at the Upper and Lower Dolores rivers; establishment was low from 1969–1988, with greater establishment occurring prior to and following this period. For P. deltoides, pulses of tree recruitment occurred along the Lower Dolores River after river damming during 1989–1993 and 2005–2008, and overall recruitment after river damming was significantly greater than that observed for unregulated rivers. Establishment of A. negundo was low at the Lower Dolores River during the last 8 years (2001–2008) of the study period. Our results suggest that flow releases from McPhee Dam into the Lower Dolores River between 1985 and 2008 provided appropriate conditions for Populus establishment, particularly at low topographic positions within the active channel in recent years, whereas A. negundo may require greater flows to bolster establishment at the higher topographic positions where it often occurs.
Medusahead (Taeniatherum caput-medusae [L.] Nevski), an exotic annual grass, is rapidly spreading and causing ecological damage across the western United States. Because this exotic plant occupies vast areas and because management resources are limited, it is critical that land managers prioritize where they direct treatment and monitoring efforts. Identifying where and by what means medusahead is spreading could provide valuable information to assist in determining where prevention and control efforts should be applied. We compared medusahead invasion levels along unimproved roads, animal trails, and random transects at 6 sites in southeastern Oregon to determine where medusahead was more common and to identify potential vectors for its spread. Medusahead was more common and its cover was greater along unimproved roads than along trails and random transects. Medusahead infestations were also larger along roads. Medusahead was more common along animal trails than along random transects, but differences were less evident. Our results suggest that medusahead spreads along roads. This outcome implies, though not conclusively, that vehicles may be one of the most important vectors for medusahead spread. Our results also suggest that animals may be a vector for medusahead dispersal; however, invasions were much more concentrated near roads than trails, suggesting that medusahead management along roads should receive higher priority. Medusahead invasion is not random across the landscape, and thus, control and monitoring efforts can be prioritized, based on potential vector pathways, to manage this invasive plant.
The Snowy Plover (Charadrius nivosus) is unique in being a determinate layer of an odd modal clutch size and in having a variable mating system in which female brood desertion occurs regularly. These traits make determining Snowy Plover offspring sex ratios important not only for long-term population stability, as the species is of conservation concern, but also for application to sex allocation theory. In this study, we determined Snowy Plover offspring sex ratios, examined differential costs of producing male and female offspring, and evaluated sex ratio variation in relation to maternal condition, habitat condition, and time during the nesting season on saline lakes of the Southern High Plains of Texas. Examination of 245 chicks from 118 clutches during 1999–2000 and 2008–2009 showed that male offspring were more costly to produce than female offspring; however, offspring sex ratio did not differ from parity, but was slightly male-biased in most years. The probability of producing a male offspring was greater both earlier and later in the breeding season than in the middle. As the availability of saline lake surface water and the subsequent availability of food vary unpredictably throughout the breeding season, depending on precipitation events, we suggest that sex ratio adjustment in unpredictable environments may not be straightforward and may follow nonlinear models and/or vary annually The effects such changes in sex ratios may have on population growth and stability remain unknown.
Measuring site quality for birds at migration stopover grounds and identifying critical stopover habitats are both important components of gauging the full life cycle conservation of migratory birds. We evaluated riparian stopover habitat quality on the San Joaquin and Mokelumne rivers in California's Central Valley for migrant Willow Flycatchers (Empidonax traillii), Orange-crowned Warblers (Oreothlypis celata), Yellow Warblers (Setophaga petechia), and Wilson's Warblers (Cardellina pusilla). For each species, we used 3 approaches to assess habitat quality: (1) we examined change in mass of individuals that were recaptured at least once; (2) we tracked body condition over the time of day and over the course of the migratory season; and (3) we compared the rates of hourly mass change for Wilson's Warbler to similar studies in Canada and the United States. On average, individuals of all species recaptured at stopover sites increased mass from initial capture to final capture (0.49 g to 0.88 g). Over the course of the day, the average condition of individuals of all study species either showed increases or remained stable, although most increases were driven by after-hatch-year birds in the population. Only Yellow and Wilson's warblers at the San Joaquin sites showed a positive relationship between capture date and condition. For Wilson's Warblers, rate of mass change was higher at California riparian sites than at other stopover sites in Canada and the United States. Our results demonstrate the importance of riparian floodplain forests in California as a stopover for migrating landbirds.
Environmentally cued hatching plasticity is a common attribute of the eggs of oviparous organisms that has been especially well studied in amphibians. Nevertheless, this process has been largely overlooked in species with complex natural histories. We exposed embryos of the rough-skinned newt (Taricha granulosa) to chemical and mechanical stimuli from multiple potential threats, including caddisfly larvae, a major predator on the egg stage of newts. Newt embryos did not exhibit hatching plasticity toward chemical cues from any treatment but, contrary to prediction, did delay hatching in response to mechanical stimuli from an egg predator. Observations of predation by caddisfly larvae on recently hatched newt embryos indicate that caddisflies may prey on multiple life history stages of T. granulosa. The results of this study indicate that hatching plasticity may be a complicated phenomenon in some taxa and that additional factors, such as toxicity of eggs or larvae and maternal behavior, may play an important role in the evolution of this phenomenon.
Basic natural history information is lacking for many bats, especially for bats of the Texas Panhandle. We examined community composition, relative abundance, and seasonal activity of bats in Palo Duro Canyon State Park, Texas, using 3 survey methods (mist net, roost surveys, and acoustic monitoring) between July 2006 and May 2009. Twelve species of bats were captured or observed, with the Brazilian free-tailed bat (Tadarida brasiliensis), canyon bat (Parastrellus hesperus), and big brown bat (Eptesicus fuscus) being the most common. Acoustic calls of 2 additional species, most likely the California myotis (Myotis californicus) and big free-tailed bat (Nyctinomops macrotis), were also recorded. The Brazilian free-tailed bat was captured year-round, and an evening bat (Nycticeius humeralis), uncommon in the area, was captured. This study increases our understanding of the occurrence, abundance, and seasonality of bats in the Texas Panhandle.
In early May 2007, northern Utah mountains experienced a period of prolonged warmer-than-normal temperatures, followed by a frost that killed or damaged much of the first-flush quaking aspen (Populus tremuloides) foliage. We assessed the effects of this transitory disturbance on the aspen bird species assemblage by comparing breeding bird survey data collected in the Bear River Mountain Range, Utah, USA, in 2005 and 2006 (predisturbance) to data from 2007 (postdisturbance). Whereas bird total abundance, species richness, and species diversity did not differ significantly among years, there were significant year-by—frost damage severity interactions, with plots with low levels of frost damage having significantly higher total abundance, richness, and diversity. Based on these results, we concluded that (1) at the landscape scale, the postdisturbance avian species assemblage was essentially identical to the predisturbance assemblage both in terms of number of individuals and species, and (2) there was a pronounced shift in the spatial distribution of birds at the stand scale, with most individuals favoring stands with low levels of frost damage over those with intermediate and high levels of frost damage. Thus, aspen stands with little or no frost damage served as refugia for birds displaced from highly impacted sites, thereby buffering any adverse effects on the avian community as a whole, at least in the short term. However, with severe climatic events predicted to become more frequent, cumulative effects of successive frost-induced defoliations on long-term avian productivity and survival may be more severe.
Most descriptions of food utilized by Peregrine Falcons (Falco peregrinus) list birds as the primary food source. Here, I report on an adult female Peregrine Falcon that learned how to acquire fish and then continually exploited this unusual source of food to feed her young.
Gizzard shad (Dorosoma cepedianum) was introduced to the Colorado River basin in 1996 as a result of unintentional stocking. It then rapidly spread into lakes and rivers in both the upper and lower Colorado River basins. We captured adult gizzard shad in the Yampa and White rivers in Colorado in 2012 during boat electrofishing surveys not specifically targeting gizzard shad. These captures document the range expansion of gizzard shad into these Green River tributaries. We also collected larval and young-of-year gizzard shad during seining surveys in backwaters of the middle Green River in 2012, thereby confirming that this species successfully reproduces and recruits in the Green River. The introduction and expansion of gizzard shad has the potential to negatively affect sport fisheries and native fish communities in the Colorado River basin.