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| Unfortunately the photograph is not sharp enough to locate the factories, nor their sizes and the materials from which the rooves were built |
The report below by J. Robbins appeared in the 1960 edition of Transactions of the Lincolnshire Naturalists' Union. In later years, another Courtaulds employee and birder, Roger Norman, also noted the phenomenon, not just on the rooves of the two original fibre-making factories but also (less frequently) on those of two others which had been built more recently. His theory was that the factories had been built on the site of a former ground-roosting site or that the birds were mistaking the rooves (constructed of unknown material) for saltpans. Courtaulds no longer exists, and it is believed the factories have long since been demolished.
During the period August-November, 1959, I was on the staff of the Courtauld’s works at Great Coates, near Grimsby.
This works was completed in 1957 and rayon staple fibre is manufactured there.
Much of the factory roof is flat and this is covered with a layer of water about 2 ins. in depth.
This is to assist in maintaining equable conditions inside the buildings throughout the year.
Soon after my arrival, I author noticed that waders were using this roof as a resting place.
Detailed observations were taken over the period 9th September-9th November inclusive.
The observations may be summarised as follows:
(i) numbers varied widely (0-3,000); large numbers occurred during daylight only at high tide in the neighbouring River Humber; at night the roof seemed to be used more freely, but it was impossible to assess numbers;
(ii) the roof was used primarily for resting; some birds (mainly Dunlin) washed in the fresh water; a few hunted for food in the sediment that has accumulated; such feeding was not governed by the tide;
(iii) Dunlin and Redshank were the species which visited the roof most regularly; their numbers and those of irregular visitors are given in the species notes below; these numbers represent only a small portion of those frequenting the Humber estuary.
The species observed were:
Lapwing: 1, bathing, 7/10.
Ringed Plover: 9 recorded on six occasions, max.: 3 on 7/10.
Common Sandpiper: Single birds on 21/9 and 29/9.
Redshank: Recorded on most days, max.: 500 on 14/10 and 4/11. This species was never observed to be feeding and rarely to be bathing.
Knot: 1, 23/9.
Little Stint: 1, 28/9; this bird fed desultorily and was associated with a Curlew Sandpiper and 9 Dunlin.
Dunlin: The commonest species, observed almost daily, max. 2,500 on 4/11, also 2,000 on 8/10. Numbers increased markedly during the first week of October. Bathing was often observed and small numbers (1-9) were observed to be feeding on several occasions in the shallower parts.
Curlew Sandpiper: 1, 28/9; 2, 7/10.
Ruff: A first-winter male fed on the drier part of the roof during the period 4-8/10. Most of this time it was escorted by a solitary Dunlin.
Other species of wader (Whimbrel, Black-tailed Godwit and Bar-tailed Godwit) were observed flying over the factory site but never on the roof.
Black-headed Gulls, occasionally, and Common and Herring Gulls, more rarely, frequented the roof, but in general these species preferred the factory reservoir.
Their numbers seemed to be independent of the state of the tide.
One passerine, the Grey Wagtail, used the roof; this species was seen on five occasions, max. 3 on 5/10; these birds were observed to feed.
House Sparrows and Pied Wagtails, both resident species at the factory, occasionally perched on the edge of the roof or, rarely, bathed.
