18 de marzo de 2020

Putting together the diet of the Great Blue Heron

My daughter loves dissecting owl pellets. When we found a large accumulation of great blue heron guano on our property, she was excited at the prospect of dissecting it. We put on some gloves and put the pellets in a set of seives with the hopes of extracting the mineralized remains of the bird's diet. Unanticipated was the massive amount of fir and feathers, which blocked the seive and generally reduced the efficacy of the process.

The great blue heron is a very versatile bird. I have only really known it as a shore bird, but it lives and hunts almost everywhere. And it doesn't neccesarily just hunt. My birding guides refer to it as an opportunistic omnivore. That means anything, anytime when the item suits it. This particular bird nest in a Douglas fir in the area, retreating to this open shed when it gets really wet and stormy. It could be feeding in ditches, ponds, tidepools, shorelines and other places beyond my imagination. At least that seems to be the case based on what we found. Bones up to about 1.25 " made up the corpus of the frass. See the associated observations of rodents, fish, egg shells, birds, crabs, dead pinnipeds and seeds. We also found a number of ~5mm well polished stones. These could have been bycatch, but maybe they were gastroliths-- the rocks and pebbles kepts in the guts of dinosaurs and birds to help mechnically break down their food. The heron, like many of its dinosaur ancestors, is a gulp and go eater. It does not chew the food so much as swallow it whole. The stones in the gut break these food items down. Would be interested in hearing from any bird people who have thoughts on what some of these prey items might be, particularly the rodent. @jamie_fenneman @jbindernagel

Ingresado el 18 de marzo de 2020 por rambryum rambryum | 10 observaciones | 2 comentarios | Deja un comentario

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