Blog #431 Sitting Low in the Nest

During incubation—the quietest time in the Osprey breeding season—the parents sit low in the nests keeping their clutches warm. Many think the nests are empty as the parent sits tight to the eggs. Sometime after Thursday, May 11, Ursula’s eggs will start to hatch, about two days apart, in the order they were laid—provided, that is, all the eggs remain viable in this unseasonably cold weather.

Ursula incubates her eggs from the Salt Point Osprey Nest Camera.


Osprey hens do the majority of daytime incubation and all of the night. Males spell their mates occasionally during the day so that they may stretch their wings, fly, eat, and perhaps bathe. However, Ospreys vary in their temperaments and inclinations toward parenting. Some females are happy to get a break after sitting for hours in the nest while others refuse to leave their eggs except for meals. Some males never incubate their eggs and only guard them from afar, whereas other males incubate for hours and only reluctantly leave the nest. Orpheus is in the latter group. His motivation to incubate is so strong that he literally pushes Ursula off the eggs.


In good weather few males show the profound interest in their eggs that Orpheus does, splitting this seemingly monotonous job with Ursula. In inclement weather, the job is all hers, and Orpheus seeks shelter in the trees. When Orpheus brings a fish to his hungry mate, she grabs it, relinquishing her clutch. However, if there is no fish, she will only switch jobs under duress. On occasion, Orpheus and Ursula get into scuffles to determine who will incubate, with the loser relegated to preen on the perch.

          

Orpheus trying to shove Ursula off her eggs from the Salt Point Osprey Nest Camera.

          

A picture containing outdoor, water, nest, bird nest Description automatically generated

Ursula lying flat on her eggs during a snow squall from the Salt Point Osprey Nest Camera.


Incubation is challenging in storms. Ursula laid low and very tight on her eggs as she and the nest were pelted with hail. Just one hit from a hail stone could fatally crack an egg. Ursula struggles in the cold, 20 mph wind gusts to shield the eggs while keeping her brood patch, a bare area of abdominal skin, in constant contact with her eggs.


For proper development, Osprey eggs must be kept around 98.5 °F, which is a few degrees shy of Orpheus’ and Ursula’s 104° F body temperatures. Both parents have brood patches equipped with temperature receptors that sense egg temperature, enabling the gestating parent to regulate the time spent incubating more accurately. The growing embryo generates its own heat, to which the parents adjust by varying the length of time they directly sit on the eggs and the tightness or closeness of their bodies to the eggs. At times, adult females may sit so tight on their eggs that the eggs appear to be missing from the nest.

A bird in a nest Description automatically generated with medium confidenceUrsula rolling her three eggs, videotaped by the Salt Point Osprey Nest Camera.


Ursula and Orpheus regularly roll and reposition the eggs throughout the day to warm the eggs evenly and to prevent embryonic membranes from sticking to the shell. The embryo inside the egg is sensitive to high temperatures and must be kept out of the sun. On warm days, adult females stand over their nests holding their wings slightly out to shade their precious eggs. Embryos are less sensitive to cold and can be left uncovered for nearly a half hour in warm weather without harm. They will perish, however, in cold and wet conditions. Humidity is important for shell development: too much can rot the egg while too little can make the shell too tough.

Look for Ursula’s eggs to begin hatching around May 11.


Eyes to the sky! 


Candace 


Candace E. Cornell 

Cayuga Lake Osprey Network

Friends of Salt Point, Lansing, NY 

cec222@gmail.com

 




EYES TO THE SKY!


READ!

 On Osprey Time: Ospreys of the Finger Lakes


VISIT!

Cayuga Lake Osprey Trail Nests Driving Tour App

Complete Cayuga Lake Osprey Trail




HELP PROTECT OSPREYS:


•Stay 300 feet away from nests during the breeding season. If they call out or fly circling the nest you are too close! 

BACK OFF IMMEDIATELY.


•Carry binoculars to view wildlife from afar.


•Help keep local waters clean, healthy, and safe.


•Recycle used fishing lines, twine, and nets, which can kill Osprey.


•Join the Cayuga Osprey Network and volunteer to help monitor Osprey nests: cec222@gmail.com.


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