The South Waterfront osprey eggs are likely to hatch in the next several days. The osprey are now on their 36th day of incubation. Osprey eggs typically hatch between 36 and 42 days of age with an average of about 37 days. Based on my calculations, today is the 36th day since incubation began.
The chicks now fill most of the interior of the eggs that was once occupied by the yoke and the albumen. A large air chamber known as an "air cell" has developing at one end of the egg. If hatching goes well, the chick will shift into a "tucking position" where it places its beak between its body and its wing and then extends its beak into the air chamber and inflate its lungs. Prior to this time, the embryo has receive all of its oxygen needs through a network of capillaries that connect to a membrane inside the egg known as the "chlorioallantois" which imports oxygen from and exports carbon dioxide to the outside world.
Once the chick has broken into the air chamber it will begin to peck at the interior of the air chamber working its way slowly around the edge. The first break through to the outside world is known as 'pipping." The process of pecking its way out of the egg can take a day or two. Chicks have a feature on their bill known as an "egg tooth" which allows then to break through the hard shell. They also have a special muscle on their neck known as a ""hatching muscle" that gives them the strength to accomplish this task. This muscle shrinks once the chick leaves the egg.
As far as we can tell there are two eggs in the nest. They were laid a couple of days apart so they are also likely to hatch a few days apart as well.
Keep a close eye on the nest for the next few days and hopefully we will see some nestlings!