Birds that forage in San Francisco Bay – particularly species like Ospreys and pelicans that feed on fish – are vulnerable to entanglement in fishing line that’s unattended or discarded. We encourage land managers to (read more…)
Ospreys are especially fascinating raptors for lots of reasons. One thing that makes them so unique is their flexibility in choosing nesting sites. Other raptors like eagles seek out trees with certain characteristics but Ospreys (read more…)
Ospreys of San Francisco Bay
Ospreys – sometimes known as “sea hawks” – are magnificent large hawks that evolved to hunt and eat fish. Their vision is over three times better than human vision so they can spot fish swimming below. The dark band around their eyes reduces glare from water. Their feet are unique among North American hawks: Rough pads on the feet help grip slippery fish, while one of their talons rotates to hold fish more aerodynamically in flight.
Ospreys build nests close to the water with materials such as sticks, moss, or seaweed. They traditionally nest on dead tree snags, but when those are not available, they often nest on human structures such as light poles, cranes, or tall platforms. In San Francisco, one Osprey pair used “caution” tape to help build their nest!
Ospreys are relatively easy to identify. Look for the white head, white breast, dark eye patch, and hooked beak. Flying overhead, their wings make a sharp M or W pattern rather than a gentle curve. Hovering over the water, they dive for their prey and then plunge their head and feet forward, grabbing the fish with their feet. You might spot an Osprey carrying a fish across the water to its chicks, to a mate sitting on the nest, or over to a perch to eat it solo.
We owe an environmental debt to Ospreys: They were one of the bird species that showed us the dangers of DDT, a toxic pesticide common in the 1950s and 60s. DDT washed into our waters and accumulated in fish and then in the Ospreys that ate them. That exposure to DDT caused Ospreys’ egg shells to become thin and break before hatching. The U.S. Environmental Protection Agency helped Ospreys survive by banning DDT in 1972. Since then, their numbers have grown from just 1,500 nesting pairs nationally in the 1970s to over 10,000 pairs today.
San Francisco Bay has seen a dramatic growth in Osprey nests in recent years. There are no records of Osprey nesting along the Bay shore before 1990, although some nested at nearby lakes. Then in 2012, fifteen nests were found along the north part of the Bay, and in 2015 there were more than thirty nests!