Yesterday morning at Bear River Migratory Bird Refuge I saw kingbirds galore – mostly Western but also a few Eastern Kingbirds. Both species are known for their penchant for perching on fences as they hunt for their insect prey.
But when they paved the 10 mile dirt/gravel access road to the refuge last year (something I’m not happy about for a variety of reasons, but that’s another story…) they also removed many of the old rustic fences with their weathered wooden posts and rusty wire and replaced them with new metal posts and shiny new wire – far from rustic and appealing. So when I happened upon this Eastern Kingbird on shiny new wire I wasn’t very enthusiastic about photographing it and I didn’t even work very hard at getting an interesting pose.
In fact I was so uninterested in the photographic prospects of the bird on the shiny wire that I took off my tc, increased my shutter speed to 1/3200 sec and waited for a take-off shot (which I never did get successfully).
But suddenly it became obvious that the kingbird was about to cast a pellet. These birds eat insects but cannot digest their chitinous exoskeletons so they regurgitate them as compacted pellets. The action is fast and it’s usually difficult to get a good look at the pellet, in the mouth or as it is flung away. But here you can see the pellet back in the throat as the kingbird tries to bring it up far enough so it can be expelled.
At this point they have a very difficult time getting it out of their throat so they vigorously shake their heads and use centrifugal force to fling it out.
The position of the head as the pellet flies out is happenstance of course. I just happened to luck out and catch the pellet clear from the beak but still enclosed within the open mandibles (I also got a catch light, something I didn’t get in most of my other shots of this bird because it was late in the morning and the sun was high). Even though this was a fairly large crop without my tc attached I was still happy to get the shot – yes, I am a behavior freak…
Early last spring I was able photograph this Western Kingbird casting a pellet with the same violent head shaking used by the Eastern Kingbird. This time the pellet was flung far to the side. (I’ve posted this shot once before).
Birds of North America Online (BNA) is my “bird bible” and when I researched their site last year they listed “no information” for pellet casting in this species, even though they did mention pellet casting as a documented behavior in Eastern Kingbirds. So when I got this shot I sent BNA a link to the photo since I figured they might be interested in a species behavior they apparently weren’t aware of. It turned out that they were and they asked for permission to use my photo, which I granted. I suspect that the photo may be used to document this behavior in Western Kingbirds when they next update their profile of the species.
I’ve long been interested in pellet formation and casting in birds – which species do it, which ones don’t, and why. Researchers study pellets to learn about diet and nutrition in birds and don’t have to kill and dissect them to do so.
And that’s a good thing…