Blog #479 The Division of Labor
Orpheus (standing) and Ursula tending their eggs, Salt Point Nest Camera.
For Ospreys raising a family is a two-bird job to ensure the best possible outcome for their offspring. Rarely is a single Osprey mother, forced by circumstance, able to raise a full brood alone even if no predators exist.
A two-parent system is usually necessary in long-lived species, especially when raising the young requires several energy-intensive months. Ospreys typically live 7–10 years, but some live 20–25 years, with the oldest recorded Osprey living well over 30 years. For these primarily monogamous piscivores maintaining communication between them and dividing domestic tasks is the basis of Osprey familial success.
Domestic duties include nest construction and maintenance, tending the offspring, and protecting the nest and family. Once a male finds a good building site, he collects hundreds of sticks for the main structure. He flies past dead tree branches and grabs them with his talons, snapping them off as he passes. For stubborn dead limbs, Ospreys sit on the tips hoping their weight will break the wood. They also use sticks lying on the ground. Other nest materials are regionally dependent. Males in the agriculturally rich Cayuga Lake Basin collect corn stalks, cow patties, large clumps of grass, and the occasional plastic bag, and other “collectable” human castoffs for the nest. Females bring softer nest linings of grass, moss, and algae and “weave” the materials into the stick nest to create a soft egg cup. Males continue remodeling the nest all summer.
Female Osprey carrying her catch aerodynamically facing forward, courtesy of Cindy Sedlacek.
Male Ospreys spend about 20% of their time hunting and the rest eating, preening, helping incubate eggs, or resting in the shade. During courting and incubation, a male guards his mate, sitting in a nearby tree or on the nestbox perch to ward off other males attempting to mate with their partners. The female spends almost all her time guarding the nest and its precious contents. It is her job to incubate the eggs, keep the hatchlings warm, tend to their needs, feed them, and keeping them shaded and cool.
Hunting is the purview of the smaller, more agile males, making them responsible for feeding themselves, their mates, and the offspring. Fishing can be extremely demanding when there is a large brood and especially in bad weather. Once a fish is caught, the male will eat all of it if he is hungry. Often, he eats just the nutrient-rich head and delivers the rest to his mate.
Orpheus delivers a fish to incubating Ursula at the nest, Salt Point Nest Camera.
Pairs typically divide incubation with females performing 80% of the task. The males spells the incubating female during the day so she can take a quick break flying, resting, and even fishing if she is extremely hungry. Orpheus incubates far more than his 20% share and often pushes Ursula off the eggs, so he has a turn. On hot days, Ursula often takes a dip in the lake to cool off and drink. Her wet feathers later help cool the young.
Since females are larger and heavier than males, they are the primary defenders of the nest. If an intruder gets too close to her nest, a female will give alarm calls, mantle or cover the nest and eggs or nestlings with her flattened body, or try to scare the offender by vocalizing and holding out her wings violently shaking them to look larger and menacing. If the intruding bird does not leave the area, she may chase it away, leaving the eggs exposed. If Orpheus is nearby, he will fly to the nest to guard the nest while Ursula is engaged.
Once the eggs hatch, females break the fish apart into small pieces and tenderly feeds these morsels to nestlings. If fishing is easy and the chicks are particularly demanding, the male will bring a whole fish to the nest. The demand for fish increases markedly as the young grow in preparation for fledging.
“Mombrella” Mother Osprey holds her wings out to shade her nestlings, courtesy of Flicker.
Guarding the nest and tending the young, especially keeping them fed and shaded from the hot sun, is laborious and draining. Females must stand entire days in the blazing hot summer sun with their wings held apart like an umbrella to create shade for the young. Osprey followers call this the “Mombrella” pose, a selfless behavior to protect the offspring from the heat and harmful UV rays of the sun. By the time the offspring are old enough to feed themselves and fledge, the adult female is exhausted. The female leaves the nest to spend a few weeks recharging her energy supplies and rebuilding flight muscles for the upcoming migration. The adult male will continue to feed its offspring well into September or until the fledges master fishing and fly south. If fishing conditions are poor the female will pitch-in to feed the nearly grown chicks until September when they all migrate separately.
Two juvenile Ospreys with orange eyes and buff feather tips, Reddit.
Much work goes into raising a baby Osprey during in the few months of summer. Without the efforts both parents protecting and feeding them, nestling Ospreys would have little chance of survival. This division of labor makes it possible for the Ospreys to raise self-sufficent offspring ready for a their arduous migration ahead.
Eyes to the sky!
Candace
Candace E. Cornell
Salt Point Natural Area
Cayuga Lake Osprey Network
EYES ON OSPREYS
WATCH!
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READ!
VISIT!
Complete Cayuga Lake Osprey Trail
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HELP PROTECT OSPREYS:
• Stay 100-300 feet away from Osprey nests during the breeding season.
If the Osprey vocalizes or flies off the nest you are too close!
BACK OFF IMMEDIATELY.
• Always carry binoculars to view wildlife from afar.
• Collect and dispose of used fishing lines, twine, nets, and plastics
which can kill Ospreys and other animals of the lakeshore
FIND A BABY OR INJURED ANIMAL?
Call the Swanson Center at 607-253-3060.
The Janet L. Swanson Wildlife Health Center, an annex of the Cornell University Hospital for Animals, is a veterinary hospital dedicated solely to the treatment of ill or injured native wild animals. They provide expert medical and surgical care for over 1,000 patients annually, from locally and across the state of New York, with the goal of releasing them back to the wild. The Wildlife Health Center operates within Cornell University, a registered nonprofit, and relies largely on public donations.
Please donate to keep these doors open.
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