Systematic Review: Edge Effects

Methods: To assess the state of the research done in the field regarding the implications of edge effects and fragmentation on nesting birds, records were identified using web of science in November 2014. The initial search for the publications was commenced utilizing the search terms ‘songbird*’ AND ‘edge effect*’ AND ‘habitat*’ AND ‘fragment*’ AND ‘edge*’. Following the search of publications on web of science, the key words of relevant articles were scanned manually. This was done to screen for any additional publications and determine whether they were related to the topic being assessed. This produced a result of 115 possible publications related to the specified fields in the search. Choosing ‘ecology’ as the research category further narrowed the publications down leaving only 75 results. All articles were then subjected to an initial title and abstract scan to test relativeness to the specified topic. The complete text of the residual articles was then processed, the articles that did not test for the implications of edge effects and habitat fragmentation on nesting birds hypothesis and secondary publications that reviewed the primary data without having their own research were excluded. Articles that focused on computer modeling and not field research were also excluded from the data collection since estimations and data modeling were used to test for possible effects. Articles that focused on the indirect effects of arthropods, ducks, vegetative regeneration, patch levels, temperature, power lines, road density and proximity to agricultural land were also excluded from since this review is focused on the effects of increasing habitat fragmentation and edge effects on the reproductive success of nesting birds. Of the initial 115 publications that were sourced, 75 were screened, 9 were removed for not being primary research articles, and 33 of the remaining 66 were directly correlated with the research topic. 33 of the remaining articles after reading the full texts were then excluded with reasons. There were 33 final primary research articles, which were included in the quantitative synthesis ranging from 1993 to 2012. Large portions of the articles were published in 1999 (9%), 2000 (12%) and 2005 (12%). All articles included in the review were published in English in a total of 12 different peer reviewed journals. Landscape ecology (21%) published the highest amount of articles for this review followed by Journal of Wildlife management (15%) and equal amounts from Ecological Applications (12%) and Biological Conservation (12%). Analysis of the literature The published primary research articles were categorized by the geographic location; some studies only mentioned the country where as others mentioned the state as well for the places where the study was conducted. Further categories included type of experiment (observational or experimental), number of species mentioned and/or utilized in the study, number of nests placed or recorded in the study, the observational gaps that researchers waited until to check up on marked nest locations to determine success or failure in reproductive success and the total duration of the study quantified by the number of breeding seasons that the data on birds was collected in. The studies that utilized point-count methods for the analysis of species present in an area did so only once every year, therefore the observational gap recorded would be 365 days. Since this would skew the results, the articles that utilized this method were not included in the analysis of observational gap vs. number of studies.