He was out near the end of the branch, so there was no possibility of climbing out there. I needed something tall to try to pull the branch down to a manageable height. Somewhere in the chaos that is the garage there was a long handled pruning saw. I called for Nick, explained the situation and asked him to get the saw. (I don't go into the garage--if you could see it, you would know why). He had a better idea. He found a long aluminum pole under the deck, part of some previous contraption. As luck would have it, it had a bent spike through one end. He hooked that over the main branch on which the robin was trapped, and hauled downward.
As the bird came towards us, we could see that his foot was caught in some very fine string. Evidently he'd been on a nest-building expedition that had gone wrong. Handing the pole over to me, Nick went to the kitchen. It took all my strength to hold that thing down. The robin was terrified. I could see his brick red chest rising and falling rapidly. Nick came back with one of our longest kitchen knives, and with the surety of Alexander cutting the Gordion knot, he sliced through the strands. In a flash of wings, the robin was gone.
Today, I keep checking all the birds in the yard to see if one is limping, but he seems to have made a full recovery. All's well that ends well.
The robin picture came from Wikimedia Commons