The organism that I plan to study is the American herring gull (Larus smithsonianus), colloquially referred to as the seagull.
I observed that the number of birds (especially seagulls) increased during periods of lower tides and decreased with higher tides. I therefore chose to observe and record changes in the number of seagulls along the tide gradient. By observing seagull abundance along the gradient (high tide, low tide, and mid tide), I was able to observe some patterns that were present in this population. I’ve included scans of my field journal observations that describe these patterns.
The underlying process that may be causing the increase in seagull numbers during low tide is that a large portion of a seagull’s diet is marine invertebrates such as crabs, mussels, and sea urchins, which are typically plucked from the surface of the shore. Therefore, it is likely that the feeding opportunities during low tide, when there is more surface area of the shore, would result in a greater abundance of seagulls in that area.
Based of these observations and reasoning, my hypothesis is:
Tidal times have an effect on the abundance of American herring gulls (Larus smithsonianus) on Pacific Coastal beaches.
Based on this hypothesis, my formal prediction is:
There will be a greater abundance of American herring gulls during low tide than during high tide.
Response variable: The number of American herring gulls. This is a continuous variable.
Explanatory variable: Type of tide (high tide or low tide). This is a categorical variable.
Below are scans of some of my field notes that document my observations and number of seagulls at three times during the same day along the tide gradient: high tide, mid tide, and low tide.
