Blog #471 Growing, Growing, Growing (sung to Rawhide)

Ursula shading and feeding her 6-week-old offspring, courtesy of Cynthia Sedlacek.

Summer feels like it’s in full swing with temperatures soaring in the 80s and 90s. When not fishing, Orpheus takes cover in the cottonwoods, but his family is fully exposed to the elements. Despite the high temperatures, life in the Salt Point nest is progressing smoothly. There have been fewer intruders pestering the family this month, which means Ursula can devote her energy and concentration to her brood. However, a second-year eagle has been carrying out reconnaissance flights past the nest frequently in the early morning, triggering momentary apprehension, but causing no harm… as yet.

The fully feathered 6-week-old chicks weigh over a pound each. When full-grown the adult males will weigh 2 pounds, and females will be up to 4.4 pounds. From week 4 until week 6, the young go through a rapid transformation as represented by the red circle around the inflection point—the so-called “super-fast growth phase”—on the familiar growth chart shown below. It is a highly vulnerable time for the chicks as their food demands are at their highest and Orpheus must work his hardest. An opportunistic feeder, Orpheus has brought home a variety of fish for his family this week including meaty white suckers, brown bullheads, carp, and a lake trout all 6 to 12 inches or more. This type of high-protein diet fuels the chicks’ final growth spurt that continues until they are two months old.

The chicks are now in the red circle indicating a phase of rapid transformation, courtesy of Lyn Adair.

“Mombrella” Ursula today with one of her chicks peaking out from her wings.

Following their “super-fast growth phase” circled the chicks enter the differentiation period where the male’s growth tapers while the females continue to grow. Females will become 20% larger than their male siblings, a form of reverse sexual dimorphism typical of raptors.

In the heat, the offspring sleep in the shadow of their mother and keep exercise to a minimum. However, whenever Orpheus brings a fish to the nest, the pile of chicks springs to life. Eagerly they rise and stretch, balancing and rocking forward on their wings as far as possible, and waddle across the nest towards their mother to enter the feeding competition. The social dynamics in the nest have changed. O’Connor no longer dominates feedings as O’Leary has become more aggressive and O’Shea no longer holds back. O’Connor and O’Leary have begun to feed themselves whenever they can snatch pieces of fish from Ursula before she divvies it out to the gaping mouths in front of her. The entire brood still depends on Ursula to keep order and provide food to each of the chicks.

Ursula continues to spend at least 8+ hours a day creating shade for her offspring by standing in her “mombrella” pose. There must be an internal mechanism that allows her wings to be locked while partially spread so as not to exhaust her energy much the way a bird’s feet lock while perched.

Everyone eagerly awaits Orpheus bringing a fish, courtesy of Cindy Sedlacek.

As human and animal parents know, raising frisky and hungry offspring is energetically taxing. Ursula not only cares for her eggs and tends to her growing youngsters, but she is also the first line of defense protecting the nest. Orpheus has the weight of feeding the family on his shoulders to keep them thriving healthy and growing.

During the hottest, sunniest of summer days, Orpheus fishes from daybreak until about noon, resuming later in the afternoon when the sun is no longer glaring. Today Orpheus caught and delivered to the nest the better part of four brown bullheads (8–12 inches) and four bluegills (4–6-inches). Adults get most of their water from the fish they eat but also drink from the lake. Osprey chicks get all their water from fish and do not taste lake water until they fledge.

Adult male bringing a fish to the nest, courtesy of Cynthia Sedlacek.

Raising baby birds is hard work for both Osprey mates. It is especially energetically stressful for Orpheus who has to catch enough fish for five hungry mouths. During the hottest summer months, Orpheus fishes from daybreak until noon. His frequency lets up a bit until late afternoon when dinner begins. Today for example was 84º and humid. Orpheus caught and delivered an impressive six 9–12 inch fish before noon, taking an average of 10 minutes to catch each fish. Ursula will probably lose about 10% of her body mass from the start to the end of the breeding season. Orpheus will lose less body mass since he can eat whenever he wants.

All birds spend a great deal of time preening their feathers, which keeps the feathers in good shape and spreads protective uropygial oils on them to maintain them. At three weeks, the nestlings begin to get their first set of adult feathers unfurling from the pin (developing) feather tracks. The hatchlings start preening as their feathers begin to push out of their sheaths, which is presumably a very itchy process. The Nest Cam confirms that once the feathers are out of their sheaths and open, the hatchlings spend a lot of time pushing, brushing, and running their beaks through them to keep them in good shape in preparation for flight.

Eyes to the sky!

Candace

Candace E. Cornell

Friends of Salt Point, Lansing, NY

Cayuga Lake Osprey Network

cec22@gmail.com

Guest photographer:

Ithaca’s Cindy Sedlacek brilliantly depicts the Ospreys of Cayuga Lake with the intimacy of a true bird lover. Enamored by the animal’s gorgeous wings and graceful flight, her work is a tribute to the power and grace of these stunning raptors.