Have not seen an attach like this but once did see a female loon with 32 chicks in tow.  They were of various ages and definitely not all loon chicks.  It was on a lake in Maine about a decade ago. 
Interesting behavior. 

Mardi Crane 

On Jul 5, 2015, at 4:53 PM, don mccabe <[log in to unmask]> wrote:

> While watching a solitary loon feeding in the middle of Norford Lake today, it gradually began swimming toward me until it was 100 ft away, then crouched low in the water, and finally dived, coming up very close to a female Hooded Merganser on the shore nearby. The loon chased the merganser who stayed inches in front of the attacking loon.  Both birds flapped wildly during the chase. This went on for about a minute and moved from the shore back to the middle of the lake. 
> Only when the merganser had drawn the loon back to the middle of the lake did it become apparent that she was hiding her brood of 6 ducklings, who she flew back to in the reeds in front of me. She escorted them, all diving in unison and staying out of sight of the loon until they made it across to the other shore. 
> Has anyone ever seen loons dining on merganser ducklings or was this another kind of attack?
> 
> Don
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