The brightly colored gape and gape reflex of a hatchling is known to stimulate the feeding response in parent birds. But besides movement and hunger, what factors influence the gape reflex in the young bird?
I suspect the stimuli changes somewhat from the nestling to the fledgling stage, but observation would have us think that gaping post-fledging occurs in response to hunger, food, and the sight of the parent, the familiar care-giver that juvenile birds recognize and follow in the days following fledging. The juvenile pictured in this post is ten days post-fledging or 28 days old, able to recognize and locate his parents and strong enough to follow them and fly to them when they bring food.
As I was watching the quiet scene below, a funny thing happened.
Above you see the male blue bird on the right, and his off-spring on the far left, sitting on a dead limb that hangs from a large oak tree in the yard. This is a favorite perch of the bluebird parents, the neighboring phoebes, and occasionally robins. In particular on this morning, one robin female frequently paused in this area before approaching her nest with food.
When she landed, the bluebird juvenile pictured below, who was sitting alone at the time, froze into the posture shown. This seemed reasonable, given the relative size of the robin and her closeness. What followed was unexpected.
Apparently the sight of the food in the robin's mouth was too much for the juvenile to resist and he flew to the robin. The robin flew up from her perch in protest, and the male bluebird quickly intervened, sending the juvenile back to his perch and the robin on her way to accomplish her mission.
In the image below, you see a second incident that followed shortly after. Again, the robin landed for a moment before approaching her nest. The juvenile was resting on the same perch. This time the juvenile gaped. But lesson learned, in part at least, he did not attempt to approach the robin.
Find instructions for making nest box predator guards by clicking the link. These guards have worked to keep the 9" arm of a raccoon out and have prevented prowling cat predation, as well as snakes. A 7-inch depth is recommended. You may also find a version of these guards at the Wild Birds Unlimited store nearest you.
Upcoming: A very attentive parent, bluebirds loving water, and juveniles at the feeder...(sweet!)