For January 6, 2011 and January 6, 2012 I compared the number of nests abandoned and the number of couples still incubating their eggs:

Year                Incubating couples           Abandoned nests       Percentage abandoned

2011                                    17                                    11                                    39%

2012                                    28                                    9                                    24%

I would not be surprised if more nests are abandoned this season.  I have two females whose mates have not yet returned to sit on the egg, and I have nests with 7 new couples this year, 2 of which have already been abandoned.  It is not unusual for some new parents to abandon their first nest.  There are 7 couples with PMRF eggs; I have never seen 100% of these hatch successfully.  Still, it looks like we will have a larger number of chicks fledge than the 10 we had last year.