A siege of egrets?

I admit I had to go online to find a collective term for egrets. I found that a group of herons are referred to as a scattering, a sedge or a siege- so I assume these apply to egrets too? My ship has been working mid way between Dakar, Senegal and the Cape Verde archipelago- for the past 10 days or so we have been circa 150+ nm from the nearest land and remarkably I have seen over a 100 egrets flying over the ocean. The birds have usually been in small flocks of 2 to 4 birds with a single flock of 8 being the largest group. All the birds have come up from the south and south west and been observed battling their way into the NE F5/6 winds that have been prevalent during my time here. Many of the birds have landed on the ship and taken advantage of the many wind-blown insects that have accumulated on the decks. I can't work out where these birds have come from or where they are trying to get to- I assume they have rounded the 'bulge' of west Africa to the SE having been displaced over the ocean and are desperately trying to get back to the coast of Mauritania or thereabouts. I have identified cattle egrets, a couple of great white egrets and what I think are probably intermediate egrets on account of their greenish lores and dark-tipped bills. All other species observed on migration here from blackcaps, redstarts, kestrels and swifts have all been heading south- as expected at this time of year- so a bit of a migration/displacement mystery to add to the many that I have encountered over the years, but a spectacle to be enjoyed anyhow. 

a chart showing my recent position

probable intermediate egret

probable GWE (left) and intermediate (right)

Flight ops.

As is so often the case, a vessels' helideck often proves attractive to passing migrants. I assume from the perspective of a migrant bird it is the most attractive, safe option- generally clear of obstructions, normally devoid of personnel due to the exhaustive HSE rules n regs. and in wet weather it is often similar to a fresh water pool- obviously attractive when flying over the open ocean. On my latest survey it attracted two cattle egrets, semipalmated plovers, a semipalmated sandpiper, two least sandpipers and several passerines including fork-tailed flycatcher and small-billed elaenia- the latter bird proving very difficult to identify as initially it was thought to be one of the Epidonax flycatchers moving down from North America. A short-tailed swift did a number of incredibly fast sorties around the ship and eventually roosted under the helideck for a nights rest. 

cattle egret

Fork-tailed flycatcher

Least sandpiper

Semipalmated plover

Short-tailed swift- at speed!

small-billed elaenia- photo. Chris McCullough.

'Fred'

We had a flock of 9 cattle egrets (I think) over the sea- 8 kept going (west!) but one peeled off, headed for the ship and then decided to take a rest on the radar mast. I prefer to see terrestrial bird species just keep going, as the longer they stay onboard the more weight they lose and the more dehydrated they become. Inevitably many die or  leave the ship looking much weaker than when they arrived-contrary to my frequent efforts to tempt many birds with fresh water. Anyway, one of the ships' officers (Gemma) decided that as this individual stayed over night 'he' should be named and so he was called 'Fred'! Who am I to argue....anyway, the following morning after a couple of false attempts 'Fred' finally decided to leave his roost and headed off over the sea- I suppose he just liked travelling solo!