These two have never lost one of their chicks (knock on wood!). This is at least their 5th year together.
I’ve seen the egg about 4 times since I posted this. Will be interesting to see how many more Mama lays!
Aliska, I went and looked them up, this pair have been together since the winter of 2007-8. She was about 4 years old when they first appeared.
They have successfully laid, raised and fledged:
2 in 2008
3 in 2009
3 in 2010
3 in 2011
So this is their 5th mating.