Abstract Thoughts
We just submitted an abstract for a poster session in the 2007 SAA meetings. Our poster will present our taphonomic studies of the shell and bone accumulations found with the eagle nests and otter den in Aniakchak Bay. Our goal for this analysis is to identify the distinctive characteristics of these non-human created ”middens”.
Ross collecting eagle nest fauna from abandoned nest at Elephant Head Point.
One intriguing observation we made in the field came when we watched the eagles at SUT-027 bringing salmon up to the nest. Twice we noticed that the eagles first removed (ate?) the head off the fish before carrying the rest of the body up to their fledgling. I don’t know why they removed the head (perhaps to lessen the weight they had to carry), but if they did this regularly then their “midden” would have the same salmon body part pattern as human sites where only the salmon fillets are transported from fish camps to the main villages.
Headless pink salmon dropped by eagle below nest at SUT-027.
We were inspired to undertake this project in part by the 2001 article in American Antiquity by Erlandson and Moss where they discuss the many different creatures that are potentially involved in forming coastal faunal assemblages. In their article they provide data they collected on an eagle nest in southeast Alaska. I think our data should be a very interesting addition, especially since we have collections from “ground” nests. I’d like to hear about any other reports of eagle or otter fauna.
“We” who?
What’s a ground nest?
I’m curious about what you noticed about what the eagles did, or what you might have learned about this.
Did you see them catch the fish too?
Did it look to you like they ate the head first, or was that just a guess? Did the birds try to carry the fish to the nest, then have to stop and remove the head? Do they have to remove the head to kill the salmon, to be able carry it up? Are salmon particularily feisty, or large?
The “we” for this study include Linda Chisholm (U of MN), Ross Smith (Portland State University), and Gina Coons (recent Hamline grad now working for an archaeology firm in Seattle).
By “ground nest” I mean that the eagle nests are on top of the sea cliffs, but accessible from the inland side. Any animal, including humans, bears, and foxes, can simply walk up to the nests and grab food scraps or even the eaglets. I’m not sure whether biologists use this term, I just wanted to distinguish our nests from regions where the eagles nest in trees or inaccessible cliff-face locations.
Yes, a few times we watched as the eagles swooped down to the stream by the Aniakchak site and snatch a salmon from the shallow waters.
Regarding the bit about eating the heads, we twice noticed this behavior. Both times the eagles caught a fish from the stream, then flew a bit down the beach before landing on a driftwood log. In both cases the eagles landed too far for me to see clearly what they were doing. But when they flew back to the nest (which is on the site and next to the stream) they returned with a headless salmon. After one of these episodes I ran down to the beach to see if I could find a ripped off head, but didn’t see any thing. The second time this happened, the eagle dropped the fish on the beach below the nest. Apparently it was struggling to get it up to the nest, but I didn’t see this happen so this is just a guess.
Pink salmon (which is the species the eagles were catching) are relatively small, weighing only 3 to 5 pounds. Normally I wouldn’t expect eagles to have any trouble flying with this size fish, but at Aniakchak they had to essentially fly straight up a 22 meter high cliff to get to their nest from the stream. My idea is that the eagles climb slowly so they need a bit of distance to get from the beach to their nest. Carrying a salmon would make the flight even more difficult.
Clearly I’m only hypothesizing that the eagles intentionally removed the salmon heads to lighten their load. I’d be really interested in any biological studies that might shed some light on this topic.
Another ‘type’ of site not created by humans that I’ve seen on Kodiak are ‘bear middens’. Last spring at upper olga lake we found areas of extremely lush vegetation - that looked like site vegetation. But test pits revealed nothing cultural. It looks like the vegetation is so lush because bears are carrying red salmon up onto the bank and into the bushes to eat them and also defecating. This has created a midden (albiet with out faunal preservation - except salmon bones from the last few years) that looks identical (even has bear dug pits that look like single room housepits) to a human created site.
We also have looked at the ‘bear middens’ at Aniakchak. We collected several piles of fresh poop in 2005, but I threw them away because they were so gnarly by the time we got them back to Hamline.
One thing we did notice were piles of beach pebbles on the bear trails. We didn’t figure these out until we found a fresh pile and realized it was also bear droppings resulting from their eating kelp or arthropods on the beach (and getting some pebbles).
I took a picture of a salmon with the head intact but an eagle had started working on the head and eaten most of the brain. I had some one Brook’s Camp tell me that the bears when they get full in the fall tend to only eat the salmon heads because they are the part that’s most rich in fats and proteins, thus providing a good source of energy. Perhaps, the eagles are doing something similar.