nubchai, Dad looked like he*d been in a terrible fight, with terrible injury to his beak, just like Mum only Mum was way worse.
We don*t know how the other Eagles came out of the fights, but we do know what happened to Mum & Dad.
When there are other, probably younger, Eagles battling for your territory, & you come out injured like that, perhaps at some point Mum & Dad decided that they just weren*t going to come out well from such fights & they needed to step away.
Maybe they*re not as young & strong as they were, or as strong as the Eagles they are battling.
So do they keep battling for their territory & getting injured, or do they step away?
So it isn*t necessarily that Dad left Em, it is possible he is waiting in the wings, but if there are other Eagles vying for Em & the territory still, then maybe it is in his best interest now to stay out of the way of fighting.