An Osprey chick at the Emma nest devours a trout.

It’s no secret that Ospreys as a species are piscivores (fish-eating animals), but just how much does a family of four consume? The Osprey nest at Emma Open Space was among the sites providing the answer this summer.

The nest was part of a research project led by Michael Academia, a fisheries biologist and graduate teaching assistant at The College of William and Mary (Williamsburg, Va.). His team of volunteer observers gathered data via Osprey nest cameras at 17 sites around the globe. Academia will compile the results for a manuscript for The Journal of Raptor Research. Among his goals was to correlate daily fish deliveries in relation to meteorological conditions such a precipitation and wind.

Academia provided Pitkin County Open Space and Trails with a brief summary of his findings at the Emma nest, where two chicks fledged this summer. Among his findings:

• 304 fish were delivered during 83 days of observation.
• On average, 3.66 fish were delivered each day.
• Trout dominated prey composition at 72 percent (see chart below).
• A statistical analysis of the significance between daily fish deliveries and meteorological conditions resulted in these findings:

1. Most fish were delivered to the nest when precipitation was under 20 millimeters.
2. When temperature ranges exceeded 15 degrees Celsius (59 degrees Fahrenheit), significantly more fish were delivered.
3. Significantly more fish were delivered to the nest when surface pressures were stable and rising, which matches similar studies.
4. When wind speed ranges and average wind speeds were under 4 meters per second at 10 meters of height, more fish were delivered to the nest, which also matches similar studies.

– Pitkin County Open Space and Trails