osprey
With a wingspan of up to 6 ft, if you get lucky you might see one of these iconic birds soaring over the water, hunting for fish. Or, along the shores of the Chesapeake Bay, you'll spot tall platforms providing nesting space for local osprey. Often, females are larger, with more brown tipped feathers on their chest than the smaller, paler males. Ospreys are piscivores, with fish making up 99% percent of their diet. They usually aim for medium sized fish, favoring Atlantic Menhaden, Perch Shad, and White Perch in the Chesapeake Bay.
Since their main source of food is live fish, Osprey have adapted to be masters at fishing. Often hunting at dawn and dusk, they glide 10-40 meters above the water, searching for shadows of fish swimming close to the surface. After spotting their next meal, they hover behind the fish for a few moments, making sure their curved claws are positioned for a clean grab. Ospreys have reversible outer toes, allowing them to make a claw ideal for catching fish, and the pointy, backwards facing scales on their talons catch as barbs in their prey. They close their nostrils, and, extending their legs, they plunge into the water feet-first, coming back with a big, fresh, fishy meal.
Osprey’s large, piercing yellow or orange eyes are specially adapted to help them be skillful predators. They have large, forward facing eyes, helping them have advanced depth perception. Raptors like Osprey often have two fovea in their eyes, small depressions on the back of the eye full of cone cells for detecting color. Humans, with only one fovea, have a smaller range of sharply detailed focus than Osprey. Osprey also have significantly denser photoreceptor cells than humans, and unique Crampton’s muscles, which assist other eye muscles in changing the curvature of the lens, allowing the birds to see at very far distances. Their superpowered eyes and quick diving allow them to spot and snag a fish before it even knows what's coming!
Osprey prefer temperate weather, and often spend winters in South America. They remember the place they were born, and every summer fly thousands of miles to return to this same area to nest. Their solo trip to and from is mostly spent over water, following the coastline. The Chesapeake Bay holds the world's largest population of breeding ospreys over the summer. However, 50 years after near extinction from the DDT ‘crisis’, Osprey are facing issues with nesting again.
In the 1950-1960s, the pesticide DDT was highly popular, in use and sprayed everywhere. DDT made its way into the water, which was taken in by marine life. The DDT in the water got ingested by plankton, which were eaten by small fish, which were then eaten by bigger fish, then finally by the osprey. In an effect called biomagnification, it builds up in each level of the food chain, causing the osprey to have more concentrated amounts of DDT. This affects their ability to regulate calcium, and their eggs had weaker, thin shells, causing many to be infertile or not survive. Osprey numbers dropped dangerously, becoming endangered, but after the banning of DDT in the 1970s and construction of nesting platforms their numbers rebounded from just a few thousand to tens of thousands. But now, ospreys are facing nesting failures again. Instead of pesticide pollution, this time ospreys are struggling because of a lack of food. Osprey’s favorite meal, the Atlantic Menhaden, has dwindling numbers. Freshly hatched chicks need plenty of nutrition, and even though the fish itself is not endangered, there needs to be a certain amount of extra fish to sustain the various life that uses them as a resource.
These osprey struggling to keep young alive indicates issues with the health of the Chesapeake Bay. Their struggles signal to scientists to keep a close eye on things like fish populations, water pollution, and weather conditions. It helps to understand food chain and population dynamics and how to help in the future. Fish like Menhaden are popular in fishing for supplemental vitamins, fertilizer, and pet food. As we can see in the struggling osprey populations, we need to keep overfishing and safe water practices in check to ensure that all life in the ocean stays healthy.
