1972 SHORT COMMUNICATlQNS 393

PHILLIPS, G. C. 1962. D. Phil. thesis, University of Oxford.

PIRRNNB, M. H. & CROMBIB, A. C. 1944. 526527.

TINBBROBN, N. 1953. The Herring Gull's world. London. TINEERQEN, N. 1964.

209-223. WORLD METEOROLOGICAL Assoc. 1956. International cloud atlas. vol. 1. Geneva.

Survival value of the white coloration of gulls and other seabirds. Unpubl.

Nature, Lond. 153 :

2061. Meded., Leiden 39 :

White plumage of seabirds.

On adaptive radiation in gulls (tribe Lm-ni).

Department of Zoology, University of Manitoba,

Winnipeg, Canada.

7 December 1971

P. J. COWAN

PACHYRAMPHUS SURINAMUS NESTING IN SURINAM

The Glossy-backed Becard Pahyramphw surinamus is a small member of the Cotingidae with a length of about 130 mm. In the male the upper head is steel blue, the rest of the upperparts are glossy bluish black with a large white patch at the base of the scapulars, and the underparts are immaculate white. In the female the crown is chestnut, the mantle grey, the lower back white, the wings black broadly edged chestnut, and the underparts white.

There is a single specimen from Obidos on the north bank of the Amazon River in Pari, Brazil, but H. Sick (in Zitt.) does not know of any further record in Brazil. Most specimens are from French Guiana where it was obtained at Cayenne, at Tamanoir on the Mana River in the west and at Pierre Saut on the Oyapock in the east (Hellmayr 1929, ' Catalogue of birds of the Americas 6 : 168-169), but the two last localities do not appear on the official map of French Guiana (1963). Though described by Linnaeus from Surinam in 1766 it was not represented in any of the major collections from that country. There are no Surinam specimens in the American Museum of Natural History at New York (E. Eisenmann, in Zitt.) nor is there a specimen in the collection brought together by Thomas E. Penard in Surinam now preserved in the Museum of Comparative Zoology at Cambridge, Mass. (Bangs & Penard 1918, ' Bull. Mus. Comp. 2001.' Harv. 62 : 26-93). I found it for the first time in Surinam in 1965 (Haverschmidt 1968, ' Birds of Surinam ') and in subsequent years I collected some more, so that I have now obtained seven specimens, all of them preserved in the Leiden Museum.

Theoe are:-Four males; Phedra (Surinam River) 10 January 1965,s February 1967, 3 September 1967 and west of Zanderij 10 August 1971 : three females: Phedra 17 October 1965, West of Zandcrij 7 November 1969 and Phedra 1 August 1971. The weight of four males is 17-5-21 g (18.6 g) and of three females 18-9-23 g (20.9 g).

It is probably not a rare bird at all, since I have collected seven specimens, but as it lives in the very tops of tall trees it may escape the notice of the casual observer. Moreover it lives in different habitats, for at Phedra, in hilly country, I found it both in the middle and along the edges of high forest, while near Zanderij it frequented typical savanna forest 04 sandy ground along the road leading westwards to the Saramacca River.

On 1 August 1971 I found an occupied nest on the edge of the forest near Phedra. It was near the top of a very tall tree, at that time partly leafless, at a height of about 45 metres. Apparently the birds had nestlings as both of them continuously flew to and fro to the nest across an open fwest clearing. After watching for some time I collected the female when it alighted in the lower branches of the tree.

Its known distribution in northern South America is restricted.

394 SHORT COMMUNICATIONS IBI8 114

F ~ ~ u ~ n 1. Nest of Pachyramphw nrriffamus on the top of a social bees’ nest of the genua Trigona. The entrance of the bird’cl nest is the upper left side.

The nest was a rounded ball with a side entrance, just like the nests of Pachyrum- pbus rufw and P. polychopteruc which I found in Surinam. It was built on a large nest of social insects which acted as the sole foundation. The insects’ nest was bottle-shaped and had a rather long and narrow entrance funnel (Fig. 1). Dr D. C. Geyskes, formerly the Surinam Government Biologist and now at the Leiden Museum, identified it from photographs as a nest of stingless bees of the genus Trigona. Previously, on 24 October 1965, also at Phedra, I had found a similar dome-shaped birds’ nest on the top of a large social insects’ nest high up in a very tall tree on the forest edge. At that time I was unable to collect the attending bird, but it was bluish black on its upperparts and immaculate white on the underparts, so that I am now certain that it was a male of P. surinamuc. The nests indicate that P. surinamus breeds in Surinam from August to October, during the long dry season, and this is supported by the fact that the male I collected near Zanderij on 10 August had greatly enlarged testes.

Van Dinther (1960, ‘ Bull. agr. Exp. Stn Suriname ’ 76 : 1-159) remarks that the members of the mainly neotropical genus Trigona form a rather distinct group in the large family of Apidae. The adults, commonly known as stingless bees because of the

1972 SHORT COMMUNICATIONS 395

vestigial and useless sting, are small black or brownish coloured social insects. In Surinam several T r igm species are known. They nibble the leaves of plants and appear to prefer tissues rich in oil and resinous products. These materials are used, together with wax secreted by the males and the workers, for the construction of their nests, especially for the funnel shaped entrance. Though unable to sting, contact with a mass of these small bees on the bare parts of the body is in my experience extremely irritating and the presence of the bees may offer the birds and their nest some protection against predators.

The gizzards of my specimens contained caterpillars (larvae of Lepidoptera), small locusts (Orthoptera : Locustidae), small cicadas (Hemiptera Hornoptera), small spiders (Araneida), a amall cockroach (Dictyoptera: Blattidae) and a few kernels of small fruits.

I am indebted to Dr D. C. Geyskes of the Leiden Museum for his comments and identification of the bees’ nest, the identification of the stomath contents and for making the line drawing from one of my photographs.

P. surinamus feeds on small insects and partly on berries and other fruits.

16 Wolfskuilstraat, Ommen,

15 January 1972 Holland

F. HAVERSCHMIDT

SEXUAL DIMORPHISM IN BREEDING CYCLES AND UNEQUAL SEX RATIO IN MAGNIFICENT FRIGATEBIRDS

In common with several other large birds, notably albatrosses and vultures (Richdale 1952, Tickell 1960, PrCvost 1961, Amadon 1964), Great Frigate-birds Fregata minor which breed successfully cannot nest in successive years because, although the population as a whole breeds annually, a successful individual cycle takes more than a year (Nelson 1967). The main features of F. minor’s breeding biology, many of which are shared by the other species of Fregata which have been studied-F. aquila on Ascension Island (Stonehouse & Stonehouse 1963) and F. ariel (with F. minor) at Aldabra, Indian Ocean (Diamond 1971)-were established by Nelson in the Galapagos Islands (Nelson 1967).

The nest-material is gathered chiefly by the male and built into the nest largely by the female, who remains on the nest to prevent nest-material being stolen by other males. The need to guard the nest prevents the female from leaving the colony before laying, as for example many Procellariiformes do, to build up food reserves for the egg; this may account for the frigate egg being one of the smallest, in relation to body weight, of any sea-bird. Both sexes incubate the single egg and brood the young for the first five or six weeks of its long fledging period. If the egg or small chick is left unguarded the nest, or its contents, will be taken by other frigates. Incubation lasts 64-8 weeks and the fledging period is 5-6 months. A most important feature of the breeding cycle is the care of the young after it has fledged. Flying young return to be fed for at least four months after fledging in F. minor and F. ariel at Aldabra (Diamond 1971), up to six months in F. minor in the Galapagos (Nelson 1967) and for as long as 14 months in F. minor at Christmas Island, Pacific Ocean (Schreiber & Ashmole 1970). This prolonged care of the young precludes annual breeding in these species since it lengthens the breeding cycle to well over a year. However, in F. minor and F. ariel (but to a lesser extent in F. apuila) colonies breed at approximately the same time each year; successful