By: Marlene Affeld
Ospreys (Pandion haliaetus), when hunting on the wing, seem to glide effortlessly over the water. Smaller than an eagle, an osprey is still an impressive raptor. With wingspans of up to 72 inches and up to 24 inches in length and a weight of almost 5 pounds, the osprey is a wonderful addition to Montana’s rich abundance of bird life.
Handsome fish hunters, the osprey has a distinctive white head and belly with rich, dark brown feathers gracing its back. The undersides of the wings are also snow-white except for dark patches and barred-brown flight feathers. Ospreys vocalize with a series of piercing whistles and chirps that become more intense if the nest is approached. Osprey nest just about anywhere in close proximity to water that provides safety and an abundance of food.
Osprey prefer to nest on the top of dead trees, however; their nests are visible on power poles, bridge trestles and rocky outcroppings. Montanans respect the osprey’s freedom and honor that by establishing nest locations. All along the rivers of Montana nest platforms especially designed for osprey safety and comfort have been installed. Such platforms are an integral part of re-establishing the osprey in areas where they have disappeared.
Even during their autumn migration to Central and South America, osprey follow the river valleys to stay close to water. Ospreys fly south from Montana in October, returning during March and April to rebuild their nests. Both the female and the male work to gather driftwood, branches and twigs to build their nest. However, it is the female of the species that does most of the labor of fabricating and crafting the nest. Ospreys assure the safety and comfort of their hatchlings by lining the nest with soft leaves and grass. Female ospreys frequently decorate their nests with bright bits of material, paper or plastic they have found.
Like the eagle, osprey will reuse nests from the previous year, patiently adding new material, repairing wind and weather damage and enlarging their comfort zone. Over time some osprey nests have grown to jaw-dropping dimensions.
The osprey's affinity for water is based on his diet which consists almost entirely of fresh fish. They rarely eat anything else. The osprey hunts by hovering over the water at altitudes of up to 200 feet, then diving feet-first to grab a tasty trout. Mother Nature has provided the osprey with extremely sharp, long claws and barbed footpads called spicules that enable it to grasp a slippery fish. The osprey also has a dense, oily plumage as well as nasal valves that prevent water from invading the nostrils when the osprey fiercely dives to capture its prey. Oddly, the feet of an osprey each have reversible front toes that facilitates their grasp in the water. However, ospreys can’t swim and several have been known to drown. This happens if they find their talons stuck in too heavy a fish and cannot become airborne.
When an osprey successfully snags a meal, it dramatically shakes its wings as it clears the water and then repositions the fish in its talons to face forward to reduce drag. The osprey will fly to a perch or if it has young, return to the nest to enjoy its meal.
In late April or early May the osprey lay their eggs. The normal clutch has three. Curiously, the eggs do not all hatch at once, with the first chick hatching up to five days before the last. Often the oldest chick becomes an overbearing bully, snatching up the choicest food brought to the nest by the parents and depriving its siblings of much needed nutrition.
The speckled appearance of osprey chicks in the nest provides excellent camouflage, however; many still fall victim to raccoons, owls and eagles. If they escape the claws of predators and are able to obtain enough food, the young ospreys will leave the nest in July or August. At about two months of age they are developed to the point of caring for themselves.
Ospreys have a complicated social structure. Normally ospreys pair for life, however; if the mating is not successful, they will seek new partners. When a female osprey chooses her mating partner, she doesn’t judge by good looks or fishing skills, but like her human counterpart, chooses the male with the best house (nest) in the best neighborhood (location). When ospreys are tired of the duties of parenthood, they will often withhold food to forcefully encourage the fledglings to leave the nest. Still wanting an adult to provide for them, osprey fledgling will often move to nearby nests where they receive food from other parent osprey.
When ospreys are 3 to 4 years old they will find a suitable partner and mate. Most male ospreys will return to the area from which they themselves fledged. The magnificent saga of the osprey continues.