We’re getting a lot of questions about the situation in Decorah. Where is DM2? What is the sub-adult doing there? Could this be one of Mom’s offspring? Let’s start with what we know!
Where is DM2?
We haven’t seen DM2 since July 11, a day before the sub-adult was first seen. Are these two things linked? It’s hard to say. We haven’t seen much of DM2 since the eaglets were taken into SOAR, which would probably seem a lot like dispersal from the eagle point of view. In reviewing footage from past years, both eagles (but Dad a little more so than Mom) weren’t seen much at all between eaglet dispersal and the beginning of nestorations in October. John also pointed out that DM2 could easily have perching places and hunting spots that we can’t see. He is an adult eagle who has developed his own preferences, so we shouldn’t expect him to behave like Dad after one nesting cycle. Still, we’re a little surprised at DM2’s complete lack of response to another eagle on territory – especially one spending so much time with Mom. Outside of Mom, any adult eagles we see on camera will be closely scrutinized and compared with our data to confirm whether or not we’re looking at DM2.
Are eagles always antagonistic toward other eagles on their home range? It depends. Eagles are often more tolerant of juvenile and sub-adult eagles, especially when they don’t have young in the nest. We’ve seen the Decorah and the Decorah North eagles accept juveniles and sub-adults, although we’ve also seen them driven away. Last year, we saw sub-adult visits in Decorah on January 28 (driven away), March 9, June 24, June 26, August 11 (spent the night with Mom), and August 18. Would DM2 accept a strange eagle on his territory for this length of time? Stranger things have been documented in the eagle world (a good example: https://www.audubon.org/news/a-rare-bald-eagle-trio-two-dads-and-mom-captivates-webcam-fans – and wouldn’t that be an interesting wrinkle!).
How old is the sub-adult?
We went to raptor expert Jerry Ligouri to get his opinion on the sub-adult’s age. He agreed that the bird was most likely four years old, but also told us that body plumage at this stage can be very unreliable. He prefers to use body plumage plus wing molt stage to confirm age when he has a bird in hand. This excellent discussion of aging golden eagles explains why: http://publications.aba.org/birding_archive_files/v36n3p278.pdf. Why were we so concerned with age verification? If the sub-adult was five, it couldn’t have been one of Mom’s offspring. Only D20, now ambassador Decorah, survived to adulthood. We’ve included pictures of both for an age comparison.
Since the sub-adult hatched in 2015, we have no way of knowing whether it is one of Mom’s offspring. Based on head shape and brow, we think it is a male. Could it be interested in Mom? Mom was 4-1/2 years old when she took up with Dad – not much older than this eagle is now. As we found out last year, a lot can happen between July and October. In short: we have a lot of questions, but very few answers. Now that we’ve answered what we can, we’re putting ourselves on Eagle Time and waiting to see how it all plays out.
We used to think that eagle life was pretty cut and dried. Eagles were monogamous, paired for life, defended their territories against all comers, and were never found in flocks (aka congregations). Like birds in general, eagles were considered rather dull. Through nest cams and field observation, we’ve learned that isn’t exactly true. Eagles are usually monogamous but can form trios. While eagle ‘divorce’ isn’t common, it happens. Eagles are quite gregarious off their range and territorial adults sometimes allow other eagles on their range. And eagles learn through experience and display preferences and interests…not something you would expect from a ‘dull’ bird. While we would all prefer more answers to our questions about the Decorah Eagles, they remain as fascinating – and elusive – as they ever have been. Our talons are already crossed for next season!
The Raptor Resource Project