Feeding, particularly at the end of season when there could be a lack of natural forage can set off robbing behaviour. For this reason it's best to feed on the top of the hive and just a little before sunset.
This year I added either empty hive boxes or ekes on top of the hives to make space for a plastic food container that is fitted with a wooden raft. The inspiration for which comes from this page which outlines a few different feeder setups.
This is what it looks like in action:
Apart from robbing behaviour, the other reason for which it is preferred to feed bees at the end of the day is that it makes the hive go absolutely nuts. It seems that once a few bees discover this sudden source of sweetness they go tell their friends. Naturally other bees will want in on the action and set off to look for this great source of forage. It should not be unexpected that they will look for food outside of the hive, that is, after all, where they usually look for nectar sources. Very quickly orientation flights will commence and the bees will scour the immediate area for the food source which is actually inside their hive.
You can see in the above video that they will also be attracted to the smallest gaps around the feeder even if they are not big enough for them to get through.
I personally feel it's best to avoid feeding all together if you can, however if you must feed, then feeding small amounts in the late evening is best. This is a particularly pertinent consideration for urban beekeepers. Though the mass amounts of bees searching the area for non-existent flowers may not act aggressively towards people, it is one of the situations where your neighbours are more likely to come into contact with your bees. In one case, when I returned 24 hours after feeding, they still had some syrup left in the feeder and they were still sending out foragers to find flowers. Upon arrival at the apiary, while I was still 75 meters away and two stories down from the hives, I already had a few bees buzzing around me.
The following video of the hive entrance starts right after the colony had been given feed. Each five second clip shows what the entrance looked like at one minute intervals. So by the end of the video you see what was happening roughly 18 minutes after feeding.