I encountered issues with my study design which prompted the need to make adjustments to it. It was pointed out to me that American robins like to inhabit a wide variety of areas irrespective of shrub density, so it doesn’t make much sense to try drawing a conclusion as to whether this factor is what’s driving the frequency of robins observed. They’re also very mobile so I may be counting robins heard/seen outside an area of a given shrub density or counting multiple times which compromises my data.
Ideally I wanted to study the effects of shrub density (in general, not any specific shrub species) on a single common bird species I saw often in the park for easier sampling but I decided it was best to switch the species of bird to one more dependent on shrubby areas for foraging/nesting and less mobile. I went back to a few sites I’m sampling from in the park to look further into other bird species I’ve seen while doing point count surveys. I found that spotted towhees (though seen less often) were almost always in beneath or near shrubs in the area, and I wasn’t seeing them in areas without much shrub cover. They’re ground-foragers, so it makes sense they also frequent these areas of high shrub density more.
I’m recording presence/absence of spotted towhees at each of the 18 sites (only counting those seen within a fixed 25 m radius over the 10 minute period). I confirmed these were 100 m or more away from each other to ensure independence. The main issues I’ve had so far with data collection have been laying down quadrats and doing point counts in higher foot traffic areas. To deal with this I’m making sure to come to the park early in the morning to prevent access issues and minimize human disturbance that might affect and potentially falsely lower the bird counts.