Plant structural complexity and mechanical defenses mediate predator-prey interactions in an odonate-bird system.

Habitat-forming species provide refuges for a variety of associating species; these refuges may mediate interactions between species differently depending on the functional traits of the habitat-forming species. We investigated refuge provisioning by plants with different functional traits for dragonfly and damselfly (Odonata: Anisoptera and Zygoptera) nymphs emerging from water bodies to molt into their adult stage. During this period, nymphs experience high levels of predation by birds. On the shores of a small pond, plants with mechanical defenses (e.g., thorns and prickles) and high structural complexity had higher abundances of odonate exuviae than nearby plants which lacked mechanical defenses and exhibited low structural complexity. To disentangle the relative effects of these two potentially important functional traits on nymph emergence-site preference and survival, we conducted two fully crossed factorial field experiments using artificial plants. Nymphs showed a strong preference for artificial plants with high structural complexity and to a lesser extent, mechanical defenses. Both functional traits increased nymph survival but through different mechanisms. We suggest that future investigations attempt to experimentally separate the elements contributing to structural complexity to elucidate the mechanistic underpinnings of refuge provisioning

The integration of climate change, spatial dynamics, and habitat fragmentation: A conceptual overview.

A growing number of studies have looked at how climate change alters the effects of habitat fragmentation and degradation on both single and multiple species; some raise concern that biodiversity loss and its effects will be exacerbated. The published literature on spatial dynamics (such as dispersal and metapopulation dynamics), habitat fragmentation and climate change requires synthesis and a conceptual framework to simplify thinking. We propose a framework that integrates how climate change affects spatial population dynamics and the effects of habitat fragmentation in terms of: (i) habitat quality, quantity and distribution; (ii) habitat connectivity; and (iii) the dynamics of habitat itself. We use the framework to categorize existing autecological studies and investigate how each is affected by anthropogenic climate change. It is clear that a changing climate produces changes in the geographic distribution of climatic conditions, and the amount and quality of habitat. The most thorough published studies show how such changes impact metapopulation persistence, source-sink dynamics, changes in species' geographic range and community composition. Climate-related changes in movement behavior and quantity, quality and distribution of habitat have also produced empirical changes in habitat connectivity for some species. An underexplored area is how habitat dynamics that are driven by climatic processes will affect species that live in dynamic habitats. We end our discussion by suggesting ways to improve current attempts to integrate climate change, spatial population dynamics and habitat fragmentation effects, and suggest distinct areas of study that might provide opportunities for more fully integrative work

The integration of climate change, spatial dynamics, and habitat fragmentation: A conceptual overview.

A growing number of studies have looked at how climate change alters the effects of habitat fragmentation and degradation on both single and multiple species; some raise concern that biodiversity loss and its effects will be exacerbated. The published literature on spatial dynamics (such as dispersal and metapopulation dynamics), habitat fragmentation and climate change requires synthesis and a conceptual framework to simplify thinking. We propose a framework that integrates how climate change affects spatial population dynamics and the effects of habitat fragmentation in terms of: (i) habitat quality, quantity and distribution; (ii) habitat connectivity; and (iii) the dynamics of habitat itself. We use the framework to categorize existing autecological studies and investigate how each is affected by anthropogenic climate change. It is clear that a changing climate produces changes in the geographic distribution of climatic conditions, and the amount and quality of habitat. The most thorough published studies show how such changes impact metapopulation persistence, source-sink dynamics, changes in species' geographic range and community composition. Climate-related changes in movement behavior and quantity, quality and distribution of habitat have also produced empirical changes in habitat connectivity for some species. An underexplored area is how habitat dynamics that are driven by climatic processes will affect species that live in dynamic habitats. We end our discussion by suggesting ways to improve current attempts to integrate climate change, spatial population dynamics and habitat fragmentation effects, and suggest distinct areas of study that might provide opportunities for more fully integrative work

Effects of conifers on aspen-breeding bird communities in the Sierra Nevada

We examined bird-habitat relationships within and across a range of aspen habitats in four major water- sheds in the eastern Sierra Nevada mountains of California and Nevada to identify habitat features of importance to aspen-breeding birds. Using point counts and vegetation assessments from 462 individual stations between 2001 and 2003 allowed us to investigate important habitat features at watershed and regional scales. Several trends were found: bird species richness and abundance were positively correlated with lower percent conifer cover, increased herbaceous cover, and lower shrub-class aspen cover. Dusky Flycatcher (Empidonax oberholseri) presence and abundance were positively correlated with increased percent shrub-class aspen cover and lower percent tree-class cover of all conifers or individual coniferous species. Warbling Vireo (Vireo gilvus) presence and abundance were positively correlated with increased percent tree-class aspen cover. The results suggest that mature aspen stands with healthy herbaceous communities and limited or no conifer intrusion are optimal habitats for aspen-breeding birds in the eastern Sierra Nevada. To maximize bird species richness and bird abundance, management actions in aspen stands should concen- trate on conifer removal, where conditions warrant, and the promotion of a healthy herbaceous layer. Conservation planning for birds in aspen habitats of the Sierra Nevada is discussed

Effects of parents and Brown-headed Cowbirds (Molothrus ater) on nest predation risk for a songbird.

Nest predation limits avian fitness, so ornithologists study nest predation, but they often only document patterns of predation rates without substantively investigating underlying mechanisms. Parental behavior and predator ecology are two fundamental drivers of predation rates and patterns, but the role of parents is less certain, particularly for songbirds. Previous work reproduced microhabitat-predation patterns experienced by Yellow Warblers (Setophaga petechia) in the Mono Lake basin at experimental nests without parents, suggesting that these patterns were driven by predator ecology rather than predator interactions with parents. In this study, we further explored effects of post-initiation parental behavior (nest defense and attendance) on predation risk by comparing natural versus experimental patterns related to territory density, seasonal timing of nest initiation, and nest age. Rates of parasitism by Brown-headed Cowbirds (Molothrus ater) were high in this system (49% nests parasitized), so we also examined parasitism-predation relationships. Natural nest predation rates (NPR) correlated negatively with breeding territory density and nonlinearly (U-shaped relationship) with nest-initiation timing, but experimental nests recorded no such patterns. After adjusting natural-nest data to control for these differences from experimental nests other than the presence of parents (e.g., defining nest failure similarly and excluding nestling-period data), we obtained similar results. Thus, parents were necessary to produce observed patterns. Lower natural NPR compared with experimental NPR suggested that parents reduced predation rates via nest defense, so this parental behavior or its consequences were likely correlated with density or seasonal timing. In contrast, daily predation rates decreased with nest age for both nest types, indicating this pattern did not involve parents. Parasitized nests suffered higher rates of partial predation but lower rates of complete predation, suggesting direct predation by cowbirds. Explicit behavioral research on parents, predators (including cowbirds), and their interactions would further illuminate mechanisms underlying the density, seasonal, and nest age patterns we observed

Mutually beneficial collaborations between residential conservation programs and academic researchers: Lessons from St. Louis

There has been growing interest in conducting biodiversity research in residential areas; however, finding suitable study sites is a challenge. Saint Louis University in Missouri has overcome this hurdle by establishing a collaboration with St. Louis Audubon’s Bring Conservation Home (BCH), the sister program to Portland’s Backyard Habitat Certification Program. We aim to highlight the elements of our partnership, the benefits to both organizations and community participants, and some challenges. BCH’s multi-tiered certification program offers a study system ideal for ecological research: a single factorial comparison of habitat differences at the local scale across a gradient of urbanization. We are investigating patterns of bee, bird and mosquito diversity across 45 BCH yards. The collaboration also offers opportunities for community engagement. We have created a citizen science project and many BCH enrollees are eager to participate and learn more about the wildlife in their yard. Additionally, we partnered with psychologists to determine whether enrollment in BCH has promoted changes in human behavior. However, challenges remain. Due to the nature of the research, additional legal and regulatory documentation was needed. Adding sub-studies also led to confusion among participants and required additional communication. In total, however, the benefits outweighed the challenges. BCH benefited from having their certification criteria empirically tested. Community members both gained and provided knowledge and felt pride in having legitimately contributed to science and conservation. We advocate for an expanded conceptualization of what collaborations with home conservation programs can be to one mutually beneficial for all stakeholders