What’s a nectar flow and how do I know if there’s one going on?
Nectar flow is when one or more major nectar sources are blooming and the weather is cooperating, allowing bees to collect the nectar. There’s a great resource that lists when native plants are blooming for a particular region, based on historical data. (In this unusually temperate year, this may not be that accurate.) Bee Forage Regions: http://honeybeenet.gsfc.nasa.gov/Honeybees/Forage.htm
Nectar, the sugar-rich liquid produced by plants to attract pollinators, occurs when there are lots of blooming plants. It is usually easy to detect pollen being carried into a hive, as bees place it in their pollen baskets (see the red and yellow bumps on their legs in the photo.) Nectar however can’t be as clearly seen.
Chances are, unless the hive is predominantly focused on raising brood and is thus bringing in as much pollen as possible, both are coming in.
Nectar is required food for grown-up honeybees; pollen, a protein, is necessary for brood-rearing. Nectar is carried into the hive via the stomachs of foraging bees; surplus nectar in the hive is amazingly transformed into honey.