NOTES Gannets robbing gulls.—On 5th August 1957, I spent the day at sea in Dingle Bay, Co. Kerry, in the trawler "Ros Brin". As soon as trawling operations began, we were accompanied by a few Storm Petrels (Hydrobates pelagicus), Fulmars (Fulmarus glacialis), Great Black-backed Gulls (Larus marinus), Lesser Black-backed Gulls (L. fuscus), and large numbers of Herring Gulls (L. argentatus). During the gutting periods, and especially when any small waste fish were thrown over-board, six to eight Gannets (Sula bassana), would join in the feast. Any fish that sank too deep for the gulls were immediately taken by the Gannets by the normal manner of diving, but on numerous occasions when a gull sitting on the surface had a fish it could not swallow quickly—i.e. small plaice, dabs and other flat fish—one or other of the Gannets would plunge in a shallow-angled frontal dive at the gull, entering the water about two yards away and snatching the fish from the gull's bill on breaking the surface. The fish was swallowed on the surface. This was repeated many times, and the Gannets also frequently fluttered along the water and snatched fish from the bills of other gulls which they passed. On several occasions, too, a Gannet was seen to lunge into the air after a retreating gull that was attempting to rise from the water with a fish; the Gannet "treading water" with wings half-open and neck fully extended upwards in its endeavour to snap the fish from the slowly rising and heavily gorged' gull. In this they were also successful. Immature Great, Lesser Black-backed and Herring Gulls were each in turn victimized, but only a few adults were attacked. The reason for this appeared to me to be the slowness of the immature birds, especially birds of the year, in swallowing the fish-food, and their inability to get out of the way quickly. J. E. FLYNN

Green Sandpiper uttering call of Wood Sandpiper.—With reference to J. M. B. King's record of "Unusual call-note of Green Sandpiper" {anted, p. 168), I was twice misled during August 1957 by a Green Sandpiper (Tringa ochropus) giving the typical call of the Wood Sandpiper (2\ glareola). Each time I was at a sugar beet factory pond near Lincoln and, as I saw the birds on the ground first, it happened that I was satisfied about their identity before I heard the call. On both occasions a party of Green Sandpipers rose together and I was most surprised to hear the "chiff-iff-iff" call of a Wood Sandpiper. The note was soon changed, or drowned by those of the other birds which were uttering the more usual "kler-wit" of the Green Sandpiper. As the birds soon settled at another pond close by, I was able to confirm my previous identification. When they were flushed a second time, only the typical Green Sandpiper alarm

537 538 BRITISH BIRDS [VOL. L notes were heard. From* my knowledge of the species, the call I heard could not be confused with the "wit-wit-wit" mentioned in The Handbook (Vol. IV, p. 311). A. D. TOWNSEND

A feeding method of Black Tern.—About mid-day on 10th August 1957, at Woodspring Bay, between Weston-super Mare and Clevedon, Somerset, a single Black Tern (Chlidonias niger) in autumn plumage was observed feeding in a manner to which there seems to be no reference in The Handbook. First seen over tidal mud and spartina grass, the Black Tern flew over the sea wall to an adjacent field of long rough grass and thistles where a few cattle were grazing. There it proceeded to fly up-wind, low over the herbage, picking food off the tops of tall plants every few yards. Reaching the windward end of the field it doubled right back down wind before beginning another foraging movement. This cycle was repeated some ten times before the tern returned over the sea wall, to disappear low over the mud bank towards the water's edge. In the next hour, however, this bird made two similar forages over this field, each of shorter duration than the first. The actual taking of the food, which appeared to consist of insects, was accomplished by hovering for an instant with a quick downward movement of head and' bill. R. ANGLES

Display and posturing of the Cuckoo.—On 6th May 1956, at close range from a car, I watched two female Cuckoos (Cuculus canorus) sitting on a fence at Aqualate, Staffordshire. A male, which had been calling near-by, alighted between them, causing one to flutter two or three yards away. This male then displayed at one of the females, but without calling and in addition to the usual postures (as described in The Handbook, Vol. II, p. 297) it rotated its tail in a large slow circle without moving the rest of its body, finishing with tail erect. This it did several times. It then flew down to the ground and returned to its perch with a dry leaf which it held for two or three seconds before flying to a wood near-by, calling repeatedly as it went. Next it returned to the second female and' repeated exactly its previous display, after which all three birds flew away. A previous note and editorial comment in British Birds (antea, vol. xlii, p. 152) refers to Cuckoos toying with twigs and grass when sexually excited, but I have not been able to find any reference to a soundless display or to the circular tail movement described above. W. G. LUTON