As birdwatchers, many tend to gloss over the subtleties of avian behavior or habit. When it comes to diet, of course we expect sparrows to be eating seeds, warblers to be after insects and accipiters and buteos to eat songbirds and rodents respectively. But, it's not really that simple...
Over the past ten days or so I've noted some interesting avian dietary behavior, and it seems that we humans may not be the only ones indulging in unusual foods during the holidays. On the Saturday after Thanksgiving I was amazed to see an immature White-crowned Sparrow in Alta Plaza Park snag a caterpillar that was nearly half of its own length (!), then chew and ingest a small bit off the end before getting spooked and retreating into cover. It then proceeded to tear off small pieces, dropping the larger fragment onto the ground, then recovered it and flew into the brush to devour the rest mostly out of sight. Lest one think that the Thanksgiving period was just an excuse for unusual carnivorous activity, a bit later that morning there was a fracas of about 45 or so crows in Lafayette Park clustered about the granaries of the now resident Acorn Woodpeckers, a mob event that Lori Lee has documented a few other times previously. They were clearly going after the stores of acorns, and though their incessant squabbling and chasing of each other considerably limited their success in those efforts, it was as if the acorns were for them a holiday nut treat.
Yesterday I made my way to Yerba Buena Gardens for lunch and to visit the museum and was pleasantly surprised when an immature Sharp-shinned Hawk flew right by and perched in one of the bare trees along the east side path. Hardly bothered by the numerous (mostly oblivious) passers-by walking just below, its attention was concentrated on the ground and surrounding bushes - the pigeons being quite distant on the other side of Mission St. (and probably too large for this little hawk anyway), and no sparrows or smaller birds to be seen. The Sharpie made a couple of passes onto the grounds and lawn, apparently going after insects; I'm reminded that "Patch" the immature Red-tailed Hawk that hung out at Alta Plaza Park a few years ago made its first hunts by catching grasshoppers and the like. Incredibly, the hawk was still there over an hour later after my museum excursion, but wasted little time as it soon swooped down across the edge of the brush to snag what appeared to be a field mouse, returning to perch briefly before thinking better of it and carrying its prey into the dense cover of the evergreen trees to the west. Clearly, accipiters eat rodents too; a matter of opportunity no doubt. iPhone photo (perched, sans prey) at http://ebird.org/ebird/view/checklist/S40935456 As we go about our search for different species and interesting visitors, take some time to watch our resident and familiar birds as well, as they are endlessly entertaining and also may reveal some surprises.
Happy holiday birding!
Richard BradusSan Francisco