The Western Grebe (Aechmophorus occidentalis) is a migratory water bird that spends its winters on the west coast of North America ranging from southeastern Alaska to the central coast of Mexico. Western Grebes spend the almost all of their time on the water, seldom straying to dry land and they forage by diving for fish. The Western Grebe is currently experiencing a population decline across its range and it a species of conservation concern in Idaho. The potential causes of this decline are not clear and greater research into Western Grebe ecology is required. The purpose of this investigation was to examine how the number of foraging dives changes with time of day. Foraging is an important part of any animal’s behavior and understanding how an individual allots its time can inform management decisions or direct future research. We observed Western Grebes at Lake Cascade in Cascade, Idaho. Observations took place over a five week period between June and July of 2017. Our observations periods were: morning (0600 – 0900); afternoon (1200 – 1500); evening (1800 – 2100). Each grebe was observed for a two minutes during which we recorded the total number of dives performed.
Results/Conclusions
We observed a total of 308 individual grebes throughout the study period. We found that Western Grebes dive more during the morning than during the evening (p < 0.05) than during any other time of day. Grebes may be meeting the majority of their foraging needs in the morning and are free to devote more time to other activities throughout the rest of the day. The lakes and reservoirs that Western Grebes inhabit are often used for human recreation. Understanding when grebes engage in vital behaviors can help inform management decisions to protect grebes during the times of day in which they are most active.