Bringing in pollen start of October, setting up for winter ?

[charentejohn]

Getting colder now and noticed they are bringing in loads of pollen mid afternoon, no idea where from and it is a dark gold colour.   I mean really busy, a bit of a scrum at the (slightly reduced) entrance coming and going.
One question is where would this be from as mostly trees at the moment no crops or gardens as in mid france countryside.  We have Ivy but can't see any on it, they head over fields and into the trees and riverside there but no idea what they are finding. 

Wondering if this is part of the build up to starting Winter Bee production by raising pollen stores.  Two hives lighter coloured and one with darker coloured bees who do behave differently in some ways but now both on pollen collection. 
I wondered as I read they use proteins in the pollen to help the winter bees live longer and enhance their immune system, so a good thing.  They are doing this in gaps in the weather and we can expect a proper winter in a month or so, therefore possible this is that buildup.  Was 5c overnight and 10c daytime a few days ago so no movement now suddely bam off they go. Winters can suddenly dip but we get warm days over winter too so they will get out and about sometimes. 
They should know what they are doing as local bees so will be in sync with the seasons here.

[TheHoneyPump]

As for what source the pollen is coming from.  There are pollen colour charts you could look at to try to figure it out.  A google search pops up a few of them.  You may also be able to find floral tables for your area which lists what blooms when.

For example:

[charentejohn]

Very helpful, thanks.  'Floral table' gave me lots of hints on table decoration    but a little re-wording once I had something to focus on found this https://www.bees-in-france.com/trees-and-plants-for-bees-in-france 

Looking at the chart the obvious culprit looks the right colour and that is - Ivy - two up and third in from the right.  Just the right colour and all in bloom now.
What I don't get is what is wrong with the Ivy nearby, I can only assume they have found a better and no dount fresher source.  Useful table.

[TheHoneyPump]

Could also try "blooming calendar" or "flowering calendar"