Nature Notes: Osprey
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by Ed Robinson
If you spend any time outdoors in Harpswell during the spring and summer months, you are sure to enjoy the sights and sounds of one of Nature’s most beautiful birds of prey. Our town has perfect habitat for ospreys, since they invariably nest near fresh or salt water. Look for large piles of sticks perched on the top of dead trees (and telephone poles if CMP doesn’t clear them out for safety reasons). Get too close and you will hear a shrill “cheereek” to warn you to keep your distance.
With a white chest, mottled brown wings, golden eyes, and black facial mask and talons, this is one striking bird. Males are lighter in color, and have more streamlined wings and bodies. The hooked beak tells you that the osprey is a serious predator. Its diet is almost completely fish, with only occasional small birds, rodents, rabbits and reptiles for variety. Unlike the owls, ospreys are active during daylight hours. After soaring more than 100 feet in the air, the osprey dives rapidly and plunges feet first into the water to grab a meal. Like the owls, the outer toe is reversible to make it easier to grip slippery fish.
The osprey is one of the largest birds you will find in our area. Up to 26 inches in length, and weighing as much as 4.5 pounds, the wing span can reach nearly 6 feet. The osprey is highly efficient in flight, making use of thermals and breezes to glide long distances without using too much energy. This is useful for seasonal migration, since the birds we see in summer spend the winter months in our Southern states, or as far south as Argentina. Ospreys can be found in Europe, Asia, Africa and Australia and fossils of the species have been dated as far back as 30 million years. In ideal conditions, their nests are renovated each year, and unless disturbed by man or storms, may be used for decades. The nest is lined with seaweed and other vegetation for insulation. After a gestation period of a month, the female lays 2-4 eggs, which hatch in about 5 weeks. Generally mated for life, both parents help in the care and feeding of the chicks, which make their maiden flights at about 2 months old. While ospreys have been known to live up to 25 years, a span of 7-10 years is more typical. Thanks to federal legislation, their only real predators are bald eagles. An eagle may take over an osprey nest, and have been known to steal young birds and fish.
Historically these wonderful birds suffered from overuse of pesticides such as DDT. Like the peregrine falcon, ospreys have made a strong recovery and there is no current concern about their number worldwide. In areas where nesting sites are sparse, nature groups often erect poles with platforms on top to give a helping hand. I love to see these graceful birds along our shores, and when I hear their high pitched whistles, I know it is time for me to move along the trail.