Tuesday, November 25, 2008

Birdie Brouhaha

A birdie brouhaha was on, and the small birds were on high alert; the mocking birds, cardinals, titmice, yellow-rumped warblers, chickadees, even the nuthatches were involved. Birds flew in and out of the bamboo thicket screaming intense alarm calls. There were no eggs or young for the birds to protect this late into autumn so what could bring that kind of response across the species line? With that much fussing I could not resist investigating its cause. The most dangerous predator to small birds are other birds, although I once witnessed a rousing mobbing of a large northern water snake that was wrapped around a tree, but that was during breeding season and the potential of a snake robbing eggs and chicks was a serious threat. I doubted a sane snake would be up the bamboo on a blustery, cool, fall day. I slipped up to the bamboo thicket’s edge, and the birds took little notice of me continuing to dive in and out of the still green bamboo. Ten minutes earlier a red-shouldered hawk leisurely flapped off when I unknowingly walked too close, and it seemed unlikely he would come back so soon with me still there. The cheeky cooper's hawk would have sneaked back and swooped over my head just for kicks, but I have no relationship with the red-shouldered, he is new to the neighborhood.

I saw no fur or feather floating down to the ground so whatever was there had not captured anyone and lunched on the unfortunate, and it seemed unlikely that these small birds would be so bold towards an unoccupied hawk. A hawk, tolerant of me, with a meal too heavy to fly easily with would stay for a while, but there were limits, and clearly, there was no meal, and no reason not to fly off...at least for a hawk. The largest bird there was a mockingbird, and although vocal, they usually are not too physically aggressive towards predators. Blue jays, absent today, will strike at enemies seemingly just for the joy of a fight, but not mockingbirds. The jays are sometimes a threat to the small bird's eggs and offspring so they do not necessarily buddy around together, but a real predator like a falcon or hawk makes all the song and small birds bedfellows and temporary allies! That the blue jays felt no need to join in was interesting, and whatever was there was not much of a threat to the jays and probably not much of a threat to the small birds either.

The would-be-predator must have shifted for the little birds dove and squealed more wildly than before. I tried to see a bit better and stuck my head into the thicket looking up, hoping to see a break in the leaves, but the leaves were too dense to see anything but green. The fuss ended as quickly as it began for the mystery predator had flown off leaving me standing there flummoxed. It was unfair, I did not have a bird's eye view to see the threat, and I did not even hear it fly away! I...did not ...even hear...it fly away...hey! Standing that close I would have heard a hawk take off, it then hit me it was an owl: a silent flier. Not a large owl, I would have seen that in the thicket, but a small owl like a screech owl. A screech also explains why it did not fly off immediately when I arrived at the thicket as screeches often freeze and blend in when they feel threatened. Different predators often receive different mobbing responses from birds; a cat strolling across an open lawn evokes a small response whereas an outed sharp shinned hawk elicits an all alarm-defcon 10 reaction. Today's mobbing was inline with screech owl mobbings I had seen before. Some times seeing animals requires more than eyes. The predator left no print, no feather, or fur, and there is no way to know what it was without a doubt, but I am pretty sure it was a screech owl.

As I have mentioned, I have seen small birds do this before with screech owls, but a sleeping owl is no threat, and a wakeful screech owl is only a small threat to the birds. Screeches mostly eat mice and insects, but as winter approaches and insects die off screeches will hunt birds more often when the opportunity arises. A screech dozing might have a better opportunity to see where birds roosts, but I am not sure that really increases hunting success. A mobbing like this takes a lot of energy, burn energy unwisely and you might die on a cold night so the birds should not be doing this just for kicks. Why such an all out response to a sleeping bird who is not an immediate threat? I do not know this for sure, but I think it creates a neighborhood bond. As the cold increases, food gets scarce the birds will be foraging in more exposed areas, and the more eyes watching for predators the better, even the ones who are competing with you for dinner. In summer, offspring were at stake and birds of many species mobbed together keeping the neighborhood save for my young keeps it safe for your young sort of alliance. But those alliances wane with the flight of the young, birds migrating south, and new winter migrants additions to the hood. I think mobbing a relatively safe predator establishes winter neighborhood bonds, and gives these birds a chance to practice the skill together, kind of like a fire drill and meet the new neighbors party- it is probably kind of fun too!

Pam Croom © 2008

1 comment:

me ann my camera said...

This was a lovely read full of wisdom of observations in the wild, which I am not so adept at, but would like to be. Recently, stepping out in my back yard, ready to get into my truck, I heard a terrific racket and turning the corner saw several Blue Jays on the fringe branches of an Alder clump, while in the center was the shape of a Hawk, I think maybe a Cooper's by its size. The Jays flew off, bringing silence to the branches, now empty except for the hawk keenly observing the silent surroundings before it too, left. Yours was a lovely post.

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