Montana Wildlife Project: Understanding the influence of landscape context and conifer encroachment of aspen habitats on songbird utilization and reproductive success

Montana Wildlife Project

Understanding the influence of landscape context and conifer encroachment of aspen habitats on songbird utilization and reproductive success

March 2009 - May 2015

Personnel

Thomas Martin, Principal Investigator

Participating Agencies

The Bair Ranch Foundation

Aspen is a critical habitat for wildlife but is rare and declining habitat in general and recognized as such throughout Western North America and the inter-mountain region. We will conduct intensive (nest success) monitoring of song bird use of aspen habitats on Bair Foundation lands and adjacent Federal and private lands to identify landscape and forest conditions that enhance diversity and reproductive success of songbirds. Concurrent studies will also occur on Fish, Wildlife and Parks management areas for additional habitat comparisons. We will focus on landscape context (slope, aspect, embedded in conifer forest vs grassland, edge of conifer forest and grassland), and aspen stand configuration (patch size, aspen tree sizes, conifer component, vegetation composition/density) to identify aspen conditions that optimize bird diversity and reproductive success. We will establish about 10 study plots of about 25 acres each in aspen stands that vary in conifer encroachment, and landscape context. We will examine overall nesting success of all bird species in these aspen stands and will simultaneously examine habitat features associated with successful nesting of individual species. We will develop predictive models of habitat features at nest patch (5 m radius) and forest stand scales that enhance reproductive success. We also will examine the conditions under which aspen regeneration is enhanced. By identifying the habitat features and relative importance of aspen stands of greatest benefits to nongame birds, we can provide clear guidance for land management for prioritizing restoration and preservation efforts.

Research Publications

Research Publications	Publication Date
LaManna, J. A., and T. E. Martin. 2017. Seasonal fecundity and consequences for λ are more strongly affected by direct than indirect predation effects across species. Ecology 98: 1829–1838	May 2017
LaManna, J. A., and T. E. Martin. 2017. Logging impacts on avian species richness and composition differ across latitudes and foraging and breeding habitat preferences. Biological Reviews 92: 1657-1674.	August 2017
LaManna, J. A., and T. E. Martin. 2015. Costs of fear: Behavioural and life-history responses to risk and their demographic consequences vary across species. Ecology Letters 19: 403–413. \| Abstract	January 2016	Behavioral responses to reduce predation risk might cause demographic ‘costs of fear’. The rare tests in terrestrial systems have focused on single species, but differences in life histories and ecology among species could yield differing costs that need to be understood to develop a general framework. Thus, we used natural and experimental variation in predation risk to test phenotypic responses and associated demographic costs for 10 songbird species. Increases in risk generally yielded increased time spent incubating eggs, which caused shorter development periods that reduce nest mortality. Parents also fed offspring less often with increased risk, but offspring maintained growth of structures used to escape predators (wings, tarsi) while sacrificing mass growth. Reproductive output from non-depredated nests declined along risk gradients, but the severity of this cost varied across species. Ultimately, phenotypic responses to predation risk are common across co-occurring species, but responses and demographic costs vary substantially.
LaManna, J. A., A. B. Hemenway, V. Boccadori, and T. E. Martin. 2015. Bird species turnover is related to changing predation risk along a vegetation gradient. Ecology 96: 1670-1680. \| Abstract	June 2015	Aspen (Populus tremuloides) forests hold a high diversity of organisms but are increasingly invaded and replaced by conifers. The consequences of this habitat change for diversity and demography of organisms, such as birds, remains poorly understood. Conifer encroachment of an aspen stand may increase bird diversity by increasing vegetation complexity. However, the presence of conifers may also impact the reproductive success of birds via addition of conifer-dependent nest predators or via changes in habitat structural complexity. We examined the effects of conifer encroachment on the diversity, reproductive success, and population growth rates of birds in fourteen aspen stands that differed in the extent of conifer encroachment in Montana, USA. Bird species diversity increased with aspen stand area but was not correlated with proportion of conifer trees in a stand. Nest predator density increased with proportion of conifer trees in a stand. Conifer encroachment directly increased nest predation rates for four of ten open-cup nesting species and indirectly increased nest predation rates for three additional open-cup nesting species. Furthermore, increased nest predation with greater conifer encroachment transformed source breeding habitat (λ > 1) into sink habitat (λ < 1) for these seven species. Based on these results, conifer encroachment into aspen stands has the potential to decrease diversity, reproductive success, and population growth rates of songbirds, which emphasizes the value of large, relatively pure aspen stands on the landscape.

Theses and Dissertations

Theses and Dissertations	Publication Date
LaManna, J. A. 2015. Predation risk and vegetation effects on avidan diversity, species turnover, reproduction and fitness. PhD degree, University of Montana. 182 pages	May 2015

Cooperative Fish and Wildlife Research Units Program: Montana Wildlife Education, Research and Technical Assistance for Managing Our Natural Resources