Why are orientation flights done en-mass?

[Sutty]

Watching a couple of hives do the mass orientation flight thing with several hundred bees or more crawling/leaving/hovering got me wondering why they all seem to do it at once & what governs the timing. I often have one hive doing this for about half an hour then a neighbouring one does it shortly after.
Any observations, pet theories, or hard evidence why it happens like this?

 

[jenkinsbrynmair]

you also have to consider that the mass orientation you are witnessing is only one kind of orientation flight - the mass one are the new younger bees on their first venture - if you look closely you will see loads of older bees at the entrance, rear ends outwards exposing their Nasonov glands and fanning to ensure these bees on their first venture out don't get 'lost' maybe they do it en masse as it's like a first school venture into the wide unknown, these bees will have all emerged around the same time so it may be logical that the older bees round them up and push them out.
I didn't know that even the older bees (especially the scout bees) orientate every morning on their first trip out, it's not like the prolonged orientation 'hover' of the massed young bees, but (according to Prof. Robert Pickard) the first thing these bees do at the entrance each morning is look downwards then upwards to recalibrate their internal navigation systems as to where 'gravity' is. they then take off and have a leisurely fly about the hive in ever increasing circles just to remind themselves where home is before scooting away on a scout.
Pickard recalled a pre dawn phonecall he once had from Cape Canaveral, it was not long after one of their space centre flights and the scientists had taken some bees with them just to see how they reacted and they were concerned as, even though the bees seemed OK, they weren't doing anything, just floating motionless around their container - he deduced the problem was that they couldn't detect gravity therefore just couldn't activate any of their usual morning 'pre flight checks' so they just froze, totally confused. When they came back to earth, they behaved like normal bees again.

 

[The Poot]

Mine seem to occur as the sun moves round the apiary with each colony in turn orienting when the sun hits the hive. (A much more scientific answer than JBM’s)

 

[jenkinsbrynmair]

Mine seem to occur as the sun moves round the apiary with each colony in turn orienting when the sun hits the hive

If that happened at the home apiary some hives would be orienting not long after sunup.
The logic of why they all don't do it at the same time makes some sense though.

 

[Sutty]

Mine are under trees and facing W or NW, their mass orientation tends to be in the afternoon.
I suspect air temperature is a factor as well as sunlight.

 

[Antipodes]

Mine are under trees and facing W or NW, their mass orientation tends to be in the afternoon.
I suspect air temperature is a factor as well as sunlight.

Yes, that's what I would have thought based on what I've seen. If it's cold and the sun is on the hives I don't see orientation flights...I notice that here now in our winter, when it's sunny but may only be 8 or 9 degrees. If it is a warmer day at this time of year (say mid teens- usually in the middle of the day) I'll see orientation flights.

 

[mbc]

you also have to consider that the mass orientation you are witnessing is only one kind of orientation flight - the mass one are the new younger bees on their first venture - if you look closely you will see loads of older bees at the entrance, rear ends outwards exposing their Nasonov glands and fanning to ensure these bees on their first venture out don't get 'lost' maybe they do it en masse as it's like a first school venture into the wide unknown, these bees will have all emerged around the same time so it may be logical that the older bees round them up and push them out.
I didn't know that even the older bees (especially the scout bees) orientate every morning on their first trip out, it's not like the prolonged orientation 'hover' of the massed young bees, but (according to Prof. Robert Pickard) the first thing these bees do at the entrance each morning is look downwards then upwards to recalibrate their internal navigation systems as to where 'gravity' is. they then take off and have a leisurely fly about the hive in ever increasing circles just to remind themselves where home is before scooting away on a scout.
Pickard recalled a pre dawn phonecall he once had from Cape Canaveral, it was not long after one of their space centre flights and the scientists had taken some bees with them just to see how they reacted and they were concerned as, even though the bees seemed OK, they weren't doing anything, just floating motionless around their container - he deduced the problem was that they couldn't detect gravity therefore just couldn't activate any of their usual morning 'pre flight checks' so they just froze, totally confused. When they came back to earth, they behaved like normal bees again.

A lot to think about in that answer, great post, diolch jbm