Blog #465 Week One: Big Eyes and Gaping Mouths

May 21, 2024

Orpheus has three more mouths to feed, Pinterest.

And it’s off to the races. Orpheus and Ursula have just six weeks to raise these three fuzzy bobbly heads into majestic hawks. No more lazy days preening in the shade for Orpheus as he must step-up his hunting three-fold. Even though this is Orpheus’s eleventh brood, he is curious about the wee creatures stirring in his nest. He typically peers in the nest cup, studying the down-covered young as Ursula lifts to readjust. His heightened attentiveness is needed now that there are three hungry young to raise. When Ursula cries out in hunger, Orpheus obeys.

Thanks to the Salt Point Nest Camera, we can watch this miraculous growth and develop of these tiny hatchlings before our eyes. Today, their wobbly heads, big eyes, and gaping mouths face their mother eagerly awaiting a snack. Ursula rips off tiny morsels of fish leftover from lunch, taking care to remove bones and hard tissues like fins, and places them in enthusiastic mouths. The largest, first-born has an obvious head-start on its siblings at feedings, pushing them aside to grab bites of fish. Although a bit smaller, the middle chick, now 3 days old, has no trouble shoving its way forward to be fed. Ursula makes sure all are fed. Once the larger chicks are satiated, Ursula tends to her vulnerable day-old chick, making sure it gets enough high-protein fish to fuel its growth. Whatever food is leftover Ursula will eat—fins, tails, and all. Since rapidly growing chicks have burgeoning appetites, mother Ospreys are often left hungry and lose weight over the breeding season, but quickly gain it back before migration.

This morning as Ursula shades her chicks and Orpheus guard, Salt Point Osprey Camera.

During their first few days, hatchlings may be fed in short stints about every 15 minutes fueling their fantastic growth. Newly hatched chicks weigh about 50 g and gain a quarter of their initial body weight each day for the first five days after hatching. In seven days, the eldest hatchling could weigh in excess of 125 g, making it double the body weight of the youngest one. The size hierarchy makes little difference in the nest provided there is ample fish. In lean times, however, it is the foundation of siblicide and brood reduction, as discussed in Blog #464.

According to Poole (2019), the demand for fish by the young family doubles and then triples in the first twenty days after the young hatch as they experience a critical growth period. This translates into a great deal of fishing ahead for Orpheus. Ospreys are like humans in that we each have individual thresholds for our behaviors: some of us are more motivated than others. There is a great variation among male Ospreys in terms of their motivation to fish and sensitivity to their mate’s comfort. Some males will respond almost immediately when their hungry mate and offspring beg for food while others seem reluctant to hunt. Orpheus has learned over the years to become responsive to his family’s needs and rarely leaves them hungry. During the nestling’s critical growth phase, males will spend a demanding 20%-30% of the day fishing. After spending a third of the day fishing, the males reach their energetic and motivational limits. If you’ve ever seen an Osprey catch a fish after a 150-foot dive, you’ll understand why.

Eyes to the sky!

Candace

Candace E. Cornell

Cayuga Lake Osprey Network

cec222@gmail.com

A black and white drawing of an eagle

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