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Switchgrass (Panicum virgatum) is a cellulosic feedstock for alternative energy production that can be grown between rows of planted pines (Pinus spp.) within intensively managed forests. Southeastern planted pine occupies 15.8 million ha and thus, switchgrass intercropping could have far-ranging effects on plant communities and biomass production within these forests if broadly implemented. Such intercropping could lead to alterations to plant communities that may cause bottom-up ecological changes affecting ecologically, economically, and socially important wildlife, such as white-tailed deer (Odocoileus virginianus; deer). Therefore, we tested whether intercropping switchgrass in loblolly pine (P. taeda) plantations would cause switchgrass to dominate vegetative biomass thereby decreasing biomass of forages and reducing white-tailed deer nutritional carrying capacity (NCC), or whether disturbance associated with establishment and harvest of switchgrass would facilitate ruderal forbs, and thereby increase biomass of preferred deer forages and increase NCC. In a randomized complete block design, we assigned 2 treatments (intercropped switchgrass and a standard pine management control) to 4 replicates of 10-ha experimental units in Kemper County, Mississippi during summers of 2011−2015. We detected 323 plant species. Intercropping switchgrass had little effect on plant biomass production, and did not affect white-tailed deer NCC at a maintenance diet of 6% crude protein. Intercropping provided additional disturbance allowing high-protein content ruderal plants to colonize, and temporarily increased (3 yr) deer NCC at the 14% crude protein diet considered necessary to support lactation. However, concomitant with a sharp increase in switchgrass biomass in the third year of the study, NCC dropped to levels similar to traditionally managed pine stands. Switchgrass intercropping is not a reliable means of increasing deer NCC as a management strategy but does not appear to reduce carrying capacity in the short-term relative to standard intensive pine management. © 2017 The Wildlife Society.

Brown-headed cowbirds (Molothrus ater) are obligate brood parasites that lay eggs in host species’ nests. Studies on effects of host nest characteristics (e.g., nest placement, concealment, nest size) on parasitism rates by brown-headed cowbirds have yielded ambiguous results. To elucidate potential relationships between nest characteristics and brood parasitism rates, we collected data from indigo bunting (Passerina cyanea; n = 68), prairie warbler (Setophaga discolor; n = 30), and yellow-breasted chat (Icteria virens; n = 127) nests from early successional, managed loblolly pine (Pinus taeda) stands in Kemper County, Mississippi, USA, during 2012–2013. We recorded concealment, percent canopy cover, nest height (m), and nest morphometrics for each nest to test how these parameters related to frequency of brown-headed cowbird nest parasitism for each species. We predicted that larger, heavier nests would have an increased likelihood of parasitism. We recorded nest parasitism of 3%, 18%, and 24% for yellow-breasted chat, indigo bunting, and prairie warbler nests, respectively. Model coefficients for nest size did not differ from zero and nest size metrics did not differ between parasitized and unparasitized nests, thus contradicting our hypotheses and findings of previous studies relating nest size to parasitism. Our results suggest that the relationship between host nests and risk of brown-headed cowbird parasitism likely varies according to species of interest, geographic location, and features of available habitat. © 2016 The Wildlife Society.

The Lake Ontario–upper St. Lawrence River (LOUSL) population of American Eels Anguilla rostrata (hereafter, “eels”) was once one of the most important groups of the species but is now in a state of serious decline. Given that thiamine deficiency has been observed in almost all of the top predators in Lake Ontario, we assessed the potential that adiet-induced thiamine deficiency associated with consumption ofAlewives Alosa pseudoharengus could be involved. Muscle thiamine was measured in eels from throughout the LOUSL corridor and was compared with putative threshold effect levels established from the literature. Mirex concentrations were used to separate Lake Ontario-resident eels from non-Lake Ontario-resident eels.Stable isotope analyses of eel muscle samples and potential prey, including Alewives, were combined with mixing model softwareto infer the diets consumed by Lake Ontario eels. Although residence in Lake Ontario was associated with a significant declinein muscle thiamine concentration, estimated Alewife consumptionby eels was unexpectedly low. Instead, mixing model results indicated that crayfish and Round Goby Neogobius melanostomus werethe major prey. Both taxa are known to contain thiaminase and have the potential to cause thiamine deficiency, but there are no reports of thiamine deficiency associated with Round Goby consumption, thus implicating crayfish. There was no recovery in thiamine levels prior to the initiation of oceanic migration. Asa result, thiamine levels of Lake Ontario-resident eels prior to migration were only slightly above putative threshold effect levels for pathological and behavioral effects in Japanese EelsAnguilla japonica, but this would require confirmation with American Eels. Since thiamine levels are expected to decline further during migration, additional effects on eel behavior, reproduction, and survival seem probable. Because of panmixia, such effects—when combined with the relatively high reproductive potential of Lake Ontario-resident eels—may have consequences for the entire species. © 2013 Taylor & Francis Group, LLC.

Summary 1. Declining abundances of forage fish and the introduction and establishment of non-indigenous species have the potential to substantially alter resource and habitat exploitation by top predators in large lakes. 2. We measured stable isotopes of carbon (δ13C) and nitrogen (δ15N) in field-collected and archived samples of Lake Ontario lake trout (Salvelinus namaycush) and five species of prey fish and compared current trophic relationships of this top predator with historical samples. 3. Relationships between δ15N and lake trout age were temporally consistent throughout Lake Ontario and confirmed the role of lake trout as a top predator in this food web. However, δ13C values for age classes of lake trout collected in 2008 ranged from 1.0 to 3.9‰ higher than those reported for the population sampled in 1992. 4. Isotope mixing models predicted that these changes in resource assimilation were owing to the replacement of rainbow smelt (Osmerus mordax) by round goby (Neogobius melanostomus) in lake trout diet and increased reliance on carbon resources derived from nearshore production. This contrasts with the historical situation in Lake Ontario where δ13C values of the lake trout population were dominated by a reliance on offshore carbon production. 5. These results indicate a reduced capacity of the Lake Ontario offshore food web to support the energetic requirements of lake trout and that this top predator has become increasingly reliant on prey resources that are derived from nearshore carbon pathways.

Guppies (Poecilia reticulata) are models for understanding the interplay between natural and sexual selection. In particular, predation has been implicated as a major force affecting female sexual preferences, male mating tactics and the level of sperm competition. When predation is high, females typically reduce their preferences for showy males and engage more in antipredator behaviours, whereas males exploit these changes by switching from sexual displays to forced matings. These patterns are thought to account for the relatively high levels of multiple paternity in high-predation populations compared to low-predation populations. Here, we assess the possible evolutionary consequences of these patterns by asking whether variation in sperm traits reflect differences in predation intensity among four pairs of Trinidadian populations: four that experience relatively low levels of predation from a gape-limited predator and four that experience relatively high levels of predation from a variety of piscivores. We found that males in high-predation populations had faster swimming sperm with longer midpieces compared to males in low-predation populations. However, we found no differences among males in high- and low-predation populations with respect to sperm number, sperm head length, flagellum length and total sperm length.