Discussion
Let's talk about that.
Where are the most suitable areas for Barn Swallows to nest? This is a complex question and will be addressed in three sections based on nesting sites, food, and the effect of livestock.
The first result to look at is where nesting sites are located and where potential sites may be. The results showed that there are 295777 potential nesting locations in Metro Vancouver. These potential sites are shown to have a heavier density in suburban and urban areas such as Vancouver, Burnaby, North Vancouver, Surrey and Langley. This is based more on the fact that these municipalities, specifically Vancouver and Burnaby have a higher density of buildings, including homes that Barn Swallows would find suitable for nesting (e.g. single family homes and small buildings). Certain areas where no suitable nesting sites were found included fields, forests and dense urban areas. In Vancouver, many areas are inhospitable due to high rise buildings (see Appendix D).
As for where the best feeding grounds are within range of the nesting sites are, is something else. Based on the optimal feeding range of Barn Swallows, which is approximately 500 meters from their nesting site, the best nesting areas can be chosen from the previously mentioned areas. Given proper insect breeding sites, the land cover classification of Metro Vancouver was given a value from 1 to 5 to show the predicted abundance of insects in the area. The total score of all the polygons was summed, therefore giving a range of possible abundances within Vancouver. This scale shows that the prime area that are suitable for Barn Swallow habitation are not areas with dense amount of nesting sites, but rather the areas with less nesting sites and higher abundances of water, farmlands and forests. Areas that showed high scores (see scores in the green zones of Appendix E) were areas such as North and West Vancouver, Lions Bay, Maple Ridge, Abbotsford and parts of Langley and Surrey. These areas had a higher chance of high insect abundance for several reasons. First, areas such as Maple Ridge and Abbotsford have a large amount of farmland and rural areas, which are good breeding areas for insects, especially in the case of the farmland being used for livestock, such as is the case in Abbotsford. Second, areas such as North and West Vancouver have a higher amount of wooded areas, which make for better breeding grounds for insects. On top of these reasons for being better feeding grounds, areas such as downtown Vancouver, Burnaby, Richmond, and central Surrey have low scores due to the fact that these are dense urban areas, which do not provide suitable breeding grounds for insects due to concrete, high rises, roads, etc. The potential nesting sites are available and denser in these areas, but make for poor habitat due to the lack of food. As a side note, there are several areas near the border between Canada and the United States that appear and show scores that are on the extreme low end of the scale. These can simply be dismissed as outliers as the study areas may have extended beyond the borders of Canada, where the data was missing, therefore skewing the score towards the low end.
As for the livestock abundance, this may have an effect on the suitability of the habitat for the Barn Swallows, but for the purposes of this project, it was only necessary to find a trend in the change of livestock in Metro Vancouver. In most municipalities, excluding Abbotsford, the livestock abundance is in decline. This would likely impact the suitability of the environment for Barn Swallows in the future. In each of these municipalities, the amount of livestock of sheep, horses, cows and pigs are all in decline, whereas chicken numbers tend to climb through the years.