UVM Theses and Dissertations
Format:
Print
Author:
Gulka, Allison
Dept./Program:
Natural Resources
Year:
2014
Degree:
NA
Abstract:
The implications of landscape fragmentation on wildlife are of increasing concern worldwide. Ecological function and biodiversity can be affected by habitat fragmentation and edge effects associated with habitat fragments. Although edge effects have been studied extensively in recent decades, the interactive effects of habitat features on multiple spatial scales are still not fully understood. The goal of my research was to elucidate these scale interactions by studying avian nesting success for multiple species at three spatial scales: landscape, patch, and microhabitat.
Large scale (201 ha) and small scale (1.5 ha) study plots were developed in the Champlain Valley of Vermont during the breeding seasons of 2010, 2011, and 2012. Data were collected from monitoring a total of 550 nests belonging to 62 bird species. Daily nest survival rates were estimated for large and small scale study plots using landscape (percent agriculture, distance to edge, and amount of edge), forest patch ; (patch size, edge type, canopy cover, and temperature gradient) and microhabitat covariates (nest concealment, nest height, insect biomass, and ambient temperature). Models were ranked based on Akaike's Information Criterion (AICc) values and weights. Results showed that patch size had a negative effect on nest survival (ie., as patch size increased, nest survival decreased), particularly in study plots with a higher proportion of agriculture-and less forest. This trend was especially true for species that were considered edge-tolerant. I also found that birds nesting within 50 meters ofthe forest edge were greatly affected by the ambient temperature at the nest and its relationship with forest structure and edge aspect.
These findings suggest that multiple spatial scales interact to influence avian reproductive success, and that edge proximity may actually be beneficial for some species, depending on the size and structure of the forest patch. Management decisions regarding bird communities in agriculturally fragmented landscapes should consider the potential reproductive advantages that edge-tolerant species may exhibit depending on extrinsic factors. Conservation strategies should be geared toward environmental characteristics that are measurable at multiple scales, focusing on those that have the potential be affected by future climate and habitat alterations.
Large scale (201 ha) and small scale (1.5 ha) study plots were developed in the Champlain Valley of Vermont during the breeding seasons of 2010, 2011, and 2012. Data were collected from monitoring a total of 550 nests belonging to 62 bird species. Daily nest survival rates were estimated for large and small scale study plots using landscape (percent agriculture, distance to edge, and amount of edge), forest patch ; (patch size, edge type, canopy cover, and temperature gradient) and microhabitat covariates (nest concealment, nest height, insect biomass, and ambient temperature). Models were ranked based on Akaike's Information Criterion (AICc) values and weights. Results showed that patch size had a negative effect on nest survival (ie., as patch size increased, nest survival decreased), particularly in study plots with a higher proportion of agriculture-and less forest. This trend was especially true for species that were considered edge-tolerant. I also found that birds nesting within 50 meters ofthe forest edge were greatly affected by the ambient temperature at the nest and its relationship with forest structure and edge aspect.
These findings suggest that multiple spatial scales interact to influence avian reproductive success, and that edge proximity may actually be beneficial for some species, depending on the size and structure of the forest patch. Management decisions regarding bird communities in agriculturally fragmented landscapes should consider the potential reproductive advantages that edge-tolerant species may exhibit depending on extrinsic factors. Conservation strategies should be geared toward environmental characteristics that are measurable at multiple scales, focusing on those that have the potential be affected by future climate and habitat alterations.