“First Egg in Norfolk”
The first egg of this season's brood was laid this afternoon at approximately 4:10 pm. The female's hunched posture in the nest was an indication that something might be happening. Sure enough we caught a brief glimpse of the egg.
Eagle eggs average from 2.75-3 inches long and 2-2.2 inches wide. The eggs are round-oval and
white. The average incubation time for eagles is about 35 days, although this pair has a history of incubating a little longer (37 days). We'll look for additional eggs over the next few days. Two eggs is the most common clutch size, although 3 is a possibility.
Now that the first egg has been laid the female will spend much of her time incubating the egg, the male will occasionally take turns as well. Both adults have developed a brood patch. This is a featherless area of skin on the eagle's abdomen. The brood patch has many blood vessels and is highly sensitive. This area is used by the adults to keep the eggs warm during incubation. The female's brood patch is generally more extensive and well developed, as she will be doing most of the incubation. The eggs will be periodically turned. This helps to maintain an even temperature and more importantly prevents the developing embryo from adhering to the membrane inside the egg.
It is not uncommon for the eggs to be left unattended for periods of time; this is not a cause for alarm. The eggs are able to retain heat for a time without a parent incubating. Parents will sometimes cover the eggs when leaving them, although this may be more to reduce possible predation then to keep them warm.