Western Grebes, (Aechmophorus occidentalis), are freshwater migratory birds found in Western North America. They are known for their colonial nesting habits and flashy mating rituals. Grebes are extremely sensitive to human interactions and difficult to study, because of that there is little scientific knowledge on grebe behaviors. Grebes dive to gather food, gather nest building materials, and escape from predators. In this poster I explore specifics of grebe dive duration and factors that effect it. How does the duration of dives vary across time of day, as well as before and after colony formation. To my knowledge, no other studies have examined whether the actual duration of the dive varies across time of day and if the colony formation would affect it. This gap in scientific knowledge makes this study important. I hypothesis that dive duration is influenced by time of day and colony formation.
Observations were taken at Cascade Lake Idaho from June 16 to July 18 2017. Methods include observing grebe dive times morning, afternoon, and evening, both before and after colony formation. Morning refers to 6:00 to 10:00, afternoon is 11:00 to 15:00, and evening is from 17:00 to 21:00. This season the grebes at Cascade Lake nested on approximately June 29th, pre colony formation refers to the period of time before this date, and post colony refers to after. A total of 91 birds and 423 dives were observed and included in this data set. Averages, standard deviation, and statistical significance were calculated using R for all data sets.
Results/Conclusions
I found that time of day seems to have no effect on the average duration of dives. The morning average is 25.5, the afternoon is 24.4, and the evening is 28 seconds. The difference between them is not statistically and my hypothesis is not supported.
I found that average dive duration pre-colony formation is 30.8 seconds. And post-colony formation it is 17.6 seconds, that difference is statistically significant (p<0.05). This data supports my hypothesis that dive duration is influenced by whether or not the birds have built their colony.
Further research would be needed to determine if my data is consistent in different locations and years, and to pick apart reasons why grebes dive for statistically significant shorter periods of time after they have nested and built their . Grebe dive times could be used as an index of Grebe dive efficiency on this declining bird species.