This is not surprising, you gave the bees their carbohydrates which they 
could forage within the hive, so all foragers leaving the hive would be 
going for pollen to balance their requirements for brood rearing.

Ruary
Quote I've had hives which  responded to sugar syrup in spring by bringing 
in extra  pollen. almost every bee  coming in was laden  with willow pollen. 
Unquote

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