Since my blog post 3 ended up not being the study route I opted to pursue, I realized that I should touch on some of those post requirement here as background for the changes to my project.
Survey area – private forest management lands adjacent to the Oyster River on Vancouver Island, BC.
H0 – there is no difference in bird species richness across different habitat types (in this case 3 types: mature CWH forest; regeneration stand; and recently harvested logging slash). I would also like to look at species diversity, but it may not be possible without being able to count all individuals (especially those that I may hear in the forest canopy but cannot count accurately).
Predictor (independent) variable – habitat type (categorical)
Response (dependent) variable – species richness (continuous)
Now for Blog 5:
When thinking about my survey plan I did some research and found a Resources Inventory Committee (RIC) publication “Inventory Methods for Forest and Grassland Songbirds” (March 1999). I used this as a guide to design my sampling plan in conjunction with a georeferenced orthographic map supplied by the private forest lands representative (Biologist). I chose the area of study because, although the forest company allows recreational access to their lands on weekends and holidays, this specific area is behind an additional gate preventing vehicle access. I decide this would be ideal to prevent survey interference caused by passing vehicles and baying hounds (it is cougar hunting season).
I planned my transects and survey points and plotted my route days in advance of heading into the field. Upon arrival at my survey area, I realized that although there was no snow coverage at my house, there still was in the survey area. For two of my survey area (open logging slash and mature forest) snow was not a hinderance to walking my pre-planned transect. However, the regeneration stand was snow covered, and this also included the road that I had intended to drive to the forested area. To address the snow issue (and since I already had to walk several kms to forested area) I opted to survey along the road that ran through the regeneration stand. I could still use 200 m spacing between the sample points, but this wasn’t truly following my planned transect.
Given the temperature was above 0οC (and the RIC standard indicated coastal winters outside breeding season would be acceptable to survey above 0οC) I was surprised to get as few detections as I did in the forest and slash habitats. The weather was also scattered cloud, and the wind was 1 on the Beaufort scale, so again both favorable for surveying outside breeding season (in coastal winters). I know it is a bit early for migrating songbirds to be present but for those species that are year-round residents, I expected more encounters. Snow was an issue for sure and it likely impacted the results in the survey, in particular the regeneration stand. With so much ground covered by snow, there was not habitat for ground gleaners to be working. Also, the trees in this stand ranged from 2 to 5 m tall and did not have cones for the granivores to be gleaning.
It was exciting to hear a Barred Owl (BDOW) and to see a Northern Goshawk (NOGO)! In the past I have seen both species in this area, so I knew there was a chance. Also, there is still mature forest in this specific area because there are several NOGO nesting sites which prevent harvest.
At present I don’t plan to change my survey plan or habitat area. I think in a few weeks the snow should be gone, and the passerines will also start to return, and I should hopefully be able to have more data. I may also consider adding more points to my transect. One minor adjustment I made in the field was moving my survey point laterally (still 200 m from last point) to avoid running water (noise distraction) or to move to an adjacent high spot to have a better viewpoint. One change also made almost immediately was waiting 2 mins before starting each survey. This would allow more time for any birds to settle before I started the survey and it also allowed me more time to catch my breath after walking through some variable terrain!
I have been thinking about species diversity versus just studying species richness in each habitat. I think it will be a challenge in the forest habitat to count individuals (e.g. how many Chestnut-backed Chickadees, CBCH, might be in the forest canopy if I rely only on auditory identification). At this time, I will count individuals when I am able and attempt to have as much data as possible. To ensure consistency with my sampling I will be sampling each of the three habitat types on the same day. I will also vary the order of sampling habitats so that each habitat gets sampled first, second, and last in case there is variable detectability throughout the morning sampling period.
Sounds like you have a good handle on your new hypothesis and sampling strategy. It could be tough if you extend your sampling into spring as your winter surveys will likely differ from spring surveys and right now you will be looking at winter and resident birds whereas you may start getting migrants back as time goes on. Something to keep in mind as you plan the rest of your sampling!
Exciting to see a NOGO!
Thanks for the feedback. I have been considering the resident vs migratory presence. In order to address this I was thinking I would postpone my survey start for at least a few weeks (this would also hopefully allow the snow, which is atypical for this area and elevation, to melt), and then also to make sure I sample all the habitat types each day I do sample. That way I could be comparing habitat use spatially, and the temporal implications would at least be somewhat addressed. i.e. As an example if I encounter a passerine, it has returned for breeding season, and it’s preferred habitat type would form part of my species richness hypothesis. I was not planning to compare presence in Feb to May, but just presence across my three habitat types within a tighter timing window.