In many bird species, males set up and defend breeding territories, and females build the nest, lay the eggs and incubate them — a division of labor that ensures the best possible outcome for their offspring. In other species, both parents feed their chicks; in still others, just the female, or just the male takes responsibility for providing food to the incubating female as well as the chicks. The latter is the case for the ospreys I have been observing at a local marsh.
Males bring the sticks to the nest, the females arrange them, forming a large nest cup surrounded by a foot or two of sticks and even leafy material around the outside. Female osprey perform almost all of the incubation, sitting on those 2-3 precious eggs for more than a month! (32-42 days), rarely getting a chance to fly off and spread their wings. The male brings her food, but she might also get some of her daily energy requirement by metabolizing some of the protein in her inactive flight muscles. (More about the implications of this in the next post.)
The female remains on the nest to protect them for at least another month, although the male might share some of this time with her. Meanwhile, he is the chief food provider, bringing as much as 6 pounds of fish to his brood and his mate on a daily basis.
Once the chicks are feathered out, grown almost to the size of the adults, and able to stand up and move around in the nest, the female takes some time off, and leaves their care to the male. Now he has to not only feed them, but guard them from potential marauding eagles or owls that might like a tasty osprey chick for dinner. (An account of this predatory behavior is described here.)
At about two months of age, having exercised their wing muscles, and practiced “helicoptering” (hovering over the nest), osprey chicks may try a test flight to a nearby tree, where they hang out, still insisting that dad come feed them.