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Monday, April 9, 2012

Hatch recalculation (April 11-12)

I went back and examined my records.  For your information, I do record every night and in the morning I log every departure and arrival, every feeding by papa, and any other events I think are significant (NOTE:  unless there is something exciting, I delete the recording after logging because they take up so much disc space).  The three eggs were laid on March 12, 14, and the last on the evening of March 16.  However, she did not begin "close sitting," meaning that she incubated the eggs essentially full time, until early on March 17. 

Some birds (including screech owls and peregrine falcons) have young that hatch synchronously (i.e. at the same time).  Bald Eagles, and many other birds, do not hatch sychronously and, as a result, one of the young may be substantially bigger than the other(s) for the first couple of days and have a significantly higher chance of survival.  In order to achieve nearly simultaneous hatching the female will delay incubation, leaving the first eggs for long periods without sitting on them.

With a reported incubation period of 26 days that means if we use March 16-17 as the start, the night of April 11-12 would be hatch night.  Last year with 6 eggs, she began close sitting after the fourth egg.  Watch with me as we learn more.

BTW, to Denise--Birds roll their eggs so that the heat from their body is distributed evenly over the eggs during incubation and so that the membrane inside the egg doesn't stick to the shell.  All, or at least most, birds roll their eggs.  Adult screech owls are about 8.5 inches tall.


Anonymous said...

Thank you . There is a national foundation that looks for volunteer data on birds such like you are collecting. I will find the link and send to you. I am from northern bergen county nj and I have seen owls on the property for the first time this year and 8.5 seems like the height I have seen at night. An entire mouse seems large for such a small animal to kill but no different than a small redtail hawk I presume. Have you seen chipmunks from the dad. We used to have about 10 around the property but have noticed only one or two lately

Grey said...

I love learning new information! This is a nice concise explanation about incubation. Thank you! I am ready to see them whenever they are ready! Looking forward to those sweet little faces-