Special Section on Canada Lynx-Habitat Relations in the Contiguous United States

Abstract The southern extent of the range of Canada lynx (Lynx canadensis) extends into the contiguous United States in locations from Washington State in the West to northern Maine in the East. Lynx persist in various habitats across this range from high-elevation wilderness to intensively managed industrial forests. Lynx habitat use at the species' southern range boundary was poorly understood before the species was listed as Threatened under the Endangered Species Act in 2000, because most research had been conducted in boreal forest. The papers in this special section outline a variety of questions regarding lynx populations at the southern extent of their range, address topics on lynx space use and denning habitat, and provide generally consistent results in terms of features important to lynx habitat use despite the wide variation in specific habitats among the study areas.     

Mass-Balance Analyses of Boreal Forest Population Cycles: Merging Demographic and Ecosystem Approaches

UsingEcopath, a trophic mass-balance modeling framework, we developed six models of a Canadian boreal forest food web centered around snowshoe hares, which have conspicuous 10-year population cycles. Detailed models of four phases of the cycle were parameterized with long-term population data for 12 vertebrate taxa. We also developed five other models that, instead of observed data, used parameter values derived from standard assumptions. Specifically, in the basic model, production was assumed to equal adult mortality, feeding rates were assumed to be allometric, and biomass was assumed to be constant. In the actual production, functional response, and biomass change models, each of these assumed values from the basic model was replaced individually by field data. Finally, constant biomass models included actual production by all species and functional responses of mammalian predators and revealed the proportion of herbivore production used by species at higher trophic levels. By comparing these models, we show that detailed information on densities and demographics was crucial to constructing models that captured dynamic aspects of the food web. These detailed models reinforced an emerging picture of the causes and consequences of the snowshoe hare cycle. The snowshoe hare decline and low phases were coincident with times when per capita production was relatively low and predation pressure high. At these times, ecotrophic efficiencies (EE) suggest there was little production that remained unconsumed by predators. The importance of both production and consumption implies that bottom–up and top–down factors interacted to cause the cycle. EEs of other herbivores (ground squirrels, red squirrels, small mammals, small birds, grouse) were generally low, suggesting weak top–down effects. Predation rates on these “alternative” prey, except ground squirrels, were highest when predators were abundant, not when hares were rare; consequently, any top–down effects reflected predator biomass and were not a function of diet composition or functional responses. Finally, several predators (lynx, coyotes, great-horned owls) showed clear bottom–up regulation, reproducing only when prey exceeded threshold densities. Taken altogether, these results demonstrate that ecosystem models parameterized by population data can describe the dynamics of nonequilibrial systems, but only when detailed information is available for the species modeled. Received 30 November 2000; Accepted 6 September 2001.     

Co-Occurrence and Occupancy of Mourning Doves and Eurasian Collared-Doves

Understanding how land cover and potential competition with invasive species shape patterns of occupancy, extirpation, and colonization of native species across a landscape can help target management for declining native populations. Mourning dove (Zenaida macroura) populations have declined throughout the United States from 1965–2015. The expansion of the Eurasian collared-dove (Streptopelia decaocto), an introduced species with similar food preferences, may further threaten mourning dove populations. We analyzed data from 2009–2016 from a large-scale monitoring program in the Western Great Plains of the United States in a 2-species occupancy model to assess the effects of collared-doves on mourning dove distributions, while accounting for imperfect detection and variation in land cover across the landscape. Mourning dove occupancy was stable or increasing across our study area, and despite overlap in resource use and co-occurrence between mourning doves and Eurasian collared-doves, we found no evidence that collared-doves are extirpating mourning doves from preferred habitat during the breeding season. © 2020 The Wildlife Society.     

Foraging behavior predicts age at independence in juvenile Eurasian dippers (Cinclus cinclus)

Timing of foraging independence may be controlled by parents,offspiing, or both and may have consequences for dispersal,reproduction, and survival In a study of juvenile Eurasian dippers(Cinclus cinchus), I examined the relationship between individualdifferences in parental provisioning, the development of foraging,and the timing of independence. Young dippers forage very differentlyfrom adults, specializing on small, stationary pre such as simuliidlarvae (Diptera), and avoiding energetically costly and highlyskilled foraging techniques, such as diving, by which adultsobtain larger prey In my Welsh study area, age at independencevaried substantially within and between broods. Juveniles thatrelied more on simuliids and less on larger prey were independentsooner, as were juveniles with higher rates of intake whileforaging the effect was obvious 3–4 days after fledging.Provisioning rate and total caloric intake over the dependentperiod was unrelated to age at independence, although greaterreliance on parental feeding was associated with higher totalcaloric intake. Higher rates of intake from begging were correlatedwith reduced foraging time. The results demonstrate that theacquisition of the adult foraging strategy is not a prerequisitefor independence or, hence, dispersal. In fact, mastering theskills necessary to capture larger prey may delay independence.Individual juvenile dippers seem to find different solutionsto the trade-off between gaining sufficient food (either frombegging or from foraging for simuliids) and the eventual necessityof learning to forage like an adult.     

Winter Prey Selection of Canada Lynx in Northwestern Montana

ABSTRACT The roles that diet and prey abundance play in habitat selection of Canada lynx (Lynx canadensis) in the contiguous United States is poorly understood. From 1998–2002, we back-tracked radiocollared lynx (6 F, 9 M) for a distance of 582 km and we located 86 kills in northwestern Montana, USA. Lynx preyed on 7 species that included blue grouse (Dendragapus obscurus), spruce grouse (Canachites canadensis), northern flying squirrel (Glaucomys sabrinus), red squirrel (Tamiasciurus hudsonicus), snowshoe hare (Lepus americanus), least weasel (Mustela nivalis), and white-tailed deer (Odocoileus virginianus). Snowshoe hares (69 kills) accounted for 96% (4-yr average, range = 94–99%) of prey biomass during the sample period. Red squirrels were the second-most-common prey (11 kills), but they only provided 2% biomass of the winter diet. Red squirrels contributed little to the lynx diet despite low hare densities. A logistic regression model of snowshoe hare, red squirrel, and grouse abundance, as indexed by the number of track crossings of use and available lynx back-tracks, was a significant (Wald statistic = 19.03, df = 3, P < 0.001) predictor of habitat use. As we expected, lynx (P < 0.001) selected use-areas with higher snowshoe hare abundance compared to random expectation. However, the red squirrel index had a weak (P = 0.087) negative relationship to lynx use, and grouse was nonsignificant (P = 0.432). Our results indicate that lynx in western Montana prey almost exclusively on snowshoe hares during the winter with little use of alternative prey. Thus, reductions in horizontal cover for hares would degrade lynx habitat.