1,721,057 research outputs found
Understanding Golden-winged warbler (Vermivora chrysoptera) breeding habitat in Western North Carolina using two different datasets: a comparison between models developed from eBird and Audubon data
No full textHabitat loss is a primary threat to biodiversity in the present day, causing many species to become endangered or extinct (Cobb 2010). Migratory birds may be especially vulnerable to habitat loss, since they rely on the persistence of two quality habitats for breeding and wintering (Taylor and Stuchbury 2016). Biologists often dedicate their research to describing patterns of distribution and abundance of species based on habitat variables, which can inform management practices and conservation efforts. Research on the habitat preferences of species in decline is needed to help prevent future extinctions.Bachelor of Scienc
Examining the Differences in Arthropod Abundance on Native vs. Non-native Plants
Full text linkA non-native plant species is one introduced to a new geographical area where it doesn’t naturally occur. As it doesn’t occur naturally, it has no natural predators and can increase in abundance and distribution, the enemy release hypothesis; therefore, non-native plants support fewer arthropods than native plants. Caterpillars, as they interact closely with plants’ secondary compounds, are expected to decrease in abundance on non-native plants while spiders who use plants for their structure and as hunting grounds will be affected the least. True bugs and beetles are expected to be moderately affected as they consume plant leaves, inert tissues, use them as hunting grounds, and for their structure. Here, I use Caterpillars Count!, a citizen science dataset, to determine how arthropod abundance—density, biomass, and occurrence—is affected by native vs. non-native plants. Analyses were done on all plant species in the dataset than on the Oleaceae and Rosaceae families with a focus on genus-level Lepidoptera richness and the arthropod abundance metrics. Caterpillars and spiders followed the expected trend, but beetles were more weakly affected while true bugs were more strongly affected. Density and occurrence supported the most Lepidoptera genera per branch. Arthropod abundance is known to be affected by evolutionary history, geographic/climatic ranges, and landscape usage. Examining how these affect arthropod abundance is important as with fewer arthropods the food web could be destabilized as insectivores like birds would have less nutritious food.Bachelor of Scienc
Foraging Niches and Resource Partitioning Between Three Co-occurring Songbirds in the Southern Appalachians
Full text linkThe Black-throated Blue Warbler (Setophaga caerulescens), Black-throated Green Warbler (Setophaga virens), and Blue-headed Vireo (Vireo solitarius) inhabit mixed hardwood and cove forests of the southern Appalachian Mountains. They are similar in that they are small, insectivorous, Neotropical migrants which obtain most of their food primarily from foliage arthropods. In the southern Appalachians, they co-occur frequently, and during the breeding season when energetic demands are high, they could be competing for limited resources. I quantified the foraging niches of these bird species and found that they have different foraging niches and that the presence of each species affects the behavior of the other species for some of the foraging characteristics studied. This suggests that competition is an important factor in determining resource partitioning between these species. These findings have implications for understanding community structure and for informing land management strategies for avian communities in the southern Appalachian Mountains.Master of Scienc
Effect of avian predation on arthropod density across tree species and regions
Full text linkMany birds rely on arthropods, especially caterpillars, to feed their young during the breeding season. The
availability of arthropods as a food resource is important for avian success. Although there are many
studies of relationships between particular species of arthropods and their host plants, there are few
characterizing the controls on arthropod density as a broad taxonomic group. I tested for top-down control
by bird predation and bottom-up control by tree species on arthropod density in two regions, The North
Carolina Piedmont and the Southern Appalachian Mountains. To test the top-down effect of birds on
arthropod density, I compared densities between tree branches that were or were not exposed to bird
predation. There was evidence of avian suppression of density for both arthropod orders commonly eaten
by birds and for caterpillars in the Piedmont, but not in the Appalachians. I tested whether tree species has
a bottom-up effect on arthropod density by calculating average arthropod densities for common tree
species in both regions. I found a bottom-up effect of tree species on overall arthropod density, with
certain regionally abundant tree species having significantly greater arthropod densities than others. I also
compiled caterpillar density data from the literature and used this, alongside caterpillar density data
presented here, as the dependent variable in variance partitioning analyses assessing the role of region,
climate (temperature and precipitation), and tree species in predicting caterpillar density across five
regions. Tree species explained more variance than climate. Climate variables included did not explain as
much variance as region, suggesting there are additional environmental variables that affect caterpillar
density. These findings could help predict where arthropods will be abundant or scarce, and thereby
predict the quality of a location as a site for insectivorous birds raising nestlings.Bachelor of Scienc
Effect of climate change on spring appearance dates in North Carolina butterflies
Full text linkRecent trends show that species are undergoing a widespread shift in the timing of life history events in accordance with global climate change. Butterflies typify this effect because they are ectothermic, and therefore sensitive to changes in temperature. Multiple studies indicate that spring appearance dates in butterflies have been occurring earlier with rising temperatures. However, these trends have not been extensively studied for the southeastern United States, a geographically diverse region that has experienced a less dramatic change in temperatures compared to that seen on a global scale. In this study, we examined changes in the date of first spring appearance between 1990 and 2014 for 65 butterfly species using a database of butterfly observations made in North Carolina. We also examined changes in the date of first appearance at the regional level by comparing the mountains, the Piedmont and the coastal regions for relative differences. Finally, we explored whether certain species-specific traits play a role in the relative changes of first flight date. Model averaging indicated that there was a trend of earlier first appearance dates over time, with an average advance of 0.6 days for each year and 3.8 days for each 1°C rise in mean temperature. There was no significant difference in the advancement of first flight date between North Carolina’s three main geographical regions. Overwintering stage and voltinism appear to be important factors for determining how North Carolina butterfly species shift their first flight dates in response to year and temperature. These results point to potential further significant shifts in butterfly arrival date as temperatures are projected to rise in the southeastern US, with possible repercussions for some butterfly species and their biological communities.Bachelor of Scienc
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
The Effect of Periodical Cicadas on Food Web Dynamics
Full text linkArthropods play critical roles in food webs as both consumers and prey for higher trophic levels, including birds. Every 13 or 17 years, millions of periodical cicadas (Magicicada spp.) emerge from the ground and create a significant biomass pulse that disrupts food web dynamics. Little research has been conducted in North Carolina on the indirect effects that periodical cicadas can have on food web dynamics, and this study aims to bridge that gap by examining their impact. We predicted that the emergence of periodical cicadas would alter bird predation on caterpillars and vary across an urbanization gradient. We deployed clay caterpillar models to assess bird predation at five different study sites throughout the summer, surveyed arthropod populations at those five sites, and performed data analysis to assess whether periodical cicadas had an indirect positive effect on caterpillar populations. We found that caterpillar abundance increased significantly during the cicada emergence, indicating a shift in bird predation from caterpillars to cicadas, but the magnitude of the effect varied across sites and was best explained by our estimates of site-level cicada density. While we observed a marginal positive relationship between urbanization and caterpillar abundance (p=0.056), this pattern is a secondary driver in the changes in caterpillar density. These findings contribute to a deeper understanding of how resource pulses, such as periodical cicada emergences, can significantly alter food web dynamics. While our findings suggest a potential link between urbanization and changes in caterpillar abundance, further research is needed to confirm these patterns. This study also has broader implications for understanding urbanization’s impact on ecosystem functions and its relevance to management strategies targeting invasive species.Bachelor of Scienc
Globally limited individual and combined effects of multiple global change factors on allometric biomass partitioning
No full textAnalysis of BirdNET and AudioMoth use in Avian Vocalization Recording and Identification
Full text linkHistorically avian population monitoring has been conducted by point counts – a process in which an individual stands in a specific location and counts every bird seen or heard during a predetermined time period. This method, however, can be expensive and time consuming. As described in this paper, we analyzed a new, automated method of avian population monitoring utilizing the AudioMoth – an autonomous recording unit – and BirdNET – an artificial neural network. We hypothesized that the new, automated method will produce more accurate avian identifications and has the potential to save countless hours spent in the field. To complete this analysis, we conducted two studies: (1) A Comparison of Avian Population Monitoring Methods and (2) Playback Experiments. In the first study we compared the effectiveness and accuracy of bird detection/identification via point counts versus manual recording analysis (MRA), which involved listening to recordings and identifying every species heard or seen on a spectrogram. We found that MRA resulted in the identification of significantly more birds for certain species, but was far more time consuming than point counts. Secondly, we ran the recordings through BirdNET’s graphical user interface (GUI). We found that BirdNET detected species that were not present and underrepresented species that were there. For the Playback Experiments, we completed three analyses: A) Effect of Distance and Frequency on Relative Amplitude Decay; B) Effect of Foliage on Relative Amplitude; and C) Effect of Relative Amplitude and Foliage on BirdNET confidence. For the Effect of Distance and Frequency analysis, we had two major findings: (1) relative amplitude decreased with distance as expected, and (2) the rate of decay was faster for higher frequency bird vocalizations. For the second analysis – Effect of Foliage on Relative Amplitude – we found that the densest foliage level showed the greatest decay in relative amplitude for four of the six species, and the lowest foliage level showed the most statistically significant relationship between frequency and relative amplitude deterioration. For the third analysis, we found that BirdNET confidence scores increased with the relative amplitude of the recordings, but there was little relationship between foliage level and BirdNET confidence. These findings have great implications for how researchers should best deploy AudioMoths when collecting recordings and monitoring avian populations in different ecosystems, as well as how much researchers should rely on artificial neural networks like BirdNET in providing accurate identifications.Bachelor of Art
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