Improving Conservation of Declining Young Forest Birds Through Adaptive Management

Early successional forest and shrubland habitats are collectively called young forest. Changes in disturbance regimes and land use conversion resulted in declines of young forest and associated wildlife across eastern North America. Conservation of declining young forest birds relies on the maintenance and creation of young forest habitats used for breeding. American Woodcock (AMWO; Scolopax minor) and Golden-winged Warbler (GWWA; Vermivora chrysoptera) are two declining young forest species. Conservation plans for both species use an adaptive management framework, which is an iterative process of planning, management actions, and monitoring and evaluation, in the context of species conservation goals. Adaptive management programs often fail to meet their conservation goals when monitoring and evaluation is missing or ineffective. To address this short coming, my research focuses on the monitoring and knowledge gathering aspects of the iterative process. First, I investigated the role of landowners in monitoring the response of AMWO to habitat management on private properties. I interviewed Wisconsin landowners to determine their monitoring preferences and then developed a pilot monitoring protocol where landowner citizen scientists documented the response of male AMWO to habitat management on their properties. I conducted sideby- side AMWO monitoring with landowners followed by an interview to gauge landowner understanding, ability, and satisfaction with the monitoring protocol. Although landowners were willing and excited to participate in AMWO monitoring, their hearing often limited their ability to collect quality data. In order to create a successful AMWO monitoring program that suits the needs of landowners and managers, I recommend in-person training, periodic hearing assessments, and flexible data submittal options. Second, I quantified the response of male GWWA to woody vegetation shearing, a best management practice intended to create quality breeding habitat. GWWA point counts and associated patch-level vegetation surveys were conducted in three habitat management types throughout Minnesota and Wisconsin (mature alder shrubland, sheared alder shrubland, and sheared aspen sapling). Using integrated likelihood models in a distance sampling framework, I investigated the impact of 1) habitat management, and 2) patch-level vegetation characteristics, on the relative abundance of male GWWA. Habitat-management type and habitat age were included in my top supported management model, and occurrence of graminoids, no woody regeneration, and 1-2m tall woody regeneration were supported habitat factors affecting male GWWA abundance. I recommend the continuation of the shearing management practice, particularly when habitat elements are missing. Finally, I tracked the migratory connectivity patterns of GWWA and Blue-winged Warbler (BWWA; Vermivora cyanoptera) in four previously unstudied populations. I used light-level geolocators deployed on male Vermivora to determine individual wintering ranges. Previous research has shown weak migratory connectivity structure in BWWA and strong migratory connectivity structure in GWWA, with GWWA breeding in the Great Lakes region wintering in Central America and those breeding in the Appalachians wintering in South America. I discovered previously unknown intricacies of GWWA migratory connectivity structure with birds from one site in the Great Lakes region wintering in Central America (n=2) and South America (n=3). I propose incorporating migratory connectivity as a criterion for population segment and conservation region designation

Vertical foraging shifts in Hawaiian forest birds in response to invasive rat removal

Worldwide, native species increasingly contend with the interacting stressors of habitat fragmentation and invasive species, yet their combined effects have rarely been examined. Direct negative effects of invasive omnivores are well documented, but the indirect effects of resource competition or those caused by predator avoidance are unknown. Here we isolated and examined the independent and interactive effects of invasive omnivorous Black rats (Rattus rattus) and forest fragment size on the interactions between avian predators and their arthropod prey. Our study examines whether invasive omnivores and ecosystem fragment size impact: 1) the vertical distribution of arthropod species composition and abundance, and 2) the vertical profile of foraging behaviors of five native and two non-native bird species found in our study system. We predicted that the reduced edge effects and greater structural complexity and canopy height of larger fragments would limit the total and proportional habitat space frequented by rats and thus limit their impact on both arthropod biomass and birds’ foraging behavior. We experimentally removed invasive omnivorous Black rats across a 100-fold (0.1 to 12 ha) size gradient of forest fragments on Hawai‘i Island, and paired foraging observations of forest passerines with arthropod sampling in the 16 rat-removed and 18 control fragments. Rat removal was associated with shifts in the vertical distribution of arthropod biomass, irrespective of fragment size. Bird foraging behavior mirrored this shift, and the impact of rat removal was greater for birds that primarily eat fruit and insects compared with those that consume nectar. Evidence from this model study system indicates that invasive rats indirectly alter the feeding behavior of native birds, and consequently impact multiple trophic levels. This study suggests that native species can modify their foraging behavior in response to invasive species removal and presumably arrival through behavioral plasticity

Vertical foraging shifts in Hawaiian forest birds in response to invasive rat removal.

Worldwide, native species increasingly contend with the interacting stressors of habitat fragmentation and invasive species, yet their combined effects have rarely been examined. Direct negative effects of invasive omnivores are well documented, but the indirect effects of resource competition or those caused by predator avoidance are unknown. Here we isolated and examined the independent and interactive effects of invasive omnivorous Black rats (Rattus rattus) and forest fragment size on the interactions between avian predators and their arthropod prey. Our study examines whether invasive omnivores and ecosystem fragment size impact: 1) the vertical distribution of arthropod species composition and abundance, and 2) the vertical profile of foraging behaviors of five native and two non-native bird species found in our study system. We predicted that the reduced edge effects and greater structural complexity and canopy height of larger fragments would limit the total and proportional habitat space frequented by rats and thus limit their impact on both arthropod biomass and birds' foraging behavior. We experimentally removed invasive omnivorous Black rats across a 100-fold (0.1 to 12 ha) size gradient of forest fragments on Hawai'i Island, and paired foraging observations of forest passerines with arthropod sampling in the 16 rat-removed and 18 control fragments. Rat removal was associated with shifts in the vertical distribution of arthropod biomass, irrespective of fragment size. Bird foraging behavior mirrored this shift, and the impact of rat removal was greater for birds that primarily eat fruit and insects compared with those that consume nectar. Evidence from this model study system indicates that invasive rats indirectly alter the feeding behavior of native birds, and consequently impact multiple trophic levels. This study suggests that native species can modify their foraging behavior in response to invasive species removal and presumably arrival through behavioral plasticity