Having observed robins and worms with the digital camera which records time as well as image I know that the robin may have a battle snaring the worm, but once caught the average worm goes down-the-hatch in under two seconds. Yesterday was exceptional. I came along as the robin was doing battle with a night crawler. Usually a worm is a skinny thing. The night crawler is a monster worm. Think stuffed kishka. I watched the robin work that worm for five minutes and it still wasn't completely eaten. From 2 seconds for dinner to over 5 minutes is a huge difference. The night crawler has to be bitten into parts to be consumed and while it's being sliced-and-diced it continues squirming.
Later in the afternoon I saw a robin on the lawn seemingly choking. On closer observation I could see what was going on. The robin had taken a huge worm and was having trouble getting it down-the-hatch. The worm was part in, part out. The robin looked like it was choking, but in reality it was trying to get the worm down. The struggle lasted one-and-a-half minutes. After that the robin resumed worm hunting. I guess there's no such thing as enough as far as robins are concerned.