Good morning. I have been carefully reading your observations and have had communications with Charlie Todd at the Maine Department of Inland Fisheries and Wildlife—Charlie has been working with eagles in Maine for decades. I would like to thank Charlie for taking the time to provide us with his extremely helpful insights. Below is a paraphrase of Charlie’s comments.
Charlie feels that a mate switch is plausible, but cannot be determined by behavioral changes because there have been instances of birds nesting successfully after mate switches and without the birds being banded there is no way for us to know for sure.
Charlie indicates that there is still a chance that they may breed, although the other pairs in the area have been on eggs since March 24th. However he notes that there is a greater percentage of birds that are inactive at this time than he would expect.
Charlie suggests that we zoom the camera out (which I will do today) to see the tree as a whole to see if we can see the birds roosting in the tree near the nest—he says it is common for non-breeding birds to can hang around the nest.
He does suggest that there is a slim chance that the birds have a new nest and that it is possible for birds to be bringing in sticks, sitting prone, and copulating at the nest site even while they are tending to another nest site. The key at this point is if we see BOTH of the birds at this nest site for longer than ten minutes. Could all of you wonderful observers please write in comments with the amount of time the birds are spending on the nest and if BOTH the birds are at the nest. When Charlie next conducts an aerial survey in the area, he will keep an eye out for a new nest.
Finally, he notes that it is comment for birds to have inactive breeding seasons, especially after a nest failure. This can be caused by old age, build up of contaminants, weather, and other factors. This pair has had the best nesting success in the state between 1995-2007, 92%. The state norm is 63%, so it is possible that these birds are sliding back to the state average.
Please keep up your excellent observations and please let me know when you see both birds on the nest and the amount of time they are at the nest.
Wing GoodaleBioDiversity Research Institute