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The Scarlet Ibis in Surinam and Trinidad

ffrench, R.P. and Haverschmidt, F. 1970.
The Scarlet Ibis in Surinam and Trinidad.
Living Bird, 9: 147–165 + 1 plate.

Abstract

This paper contains results of studies of colonies of the Scarlet Ibis (Eudocimus ruber) in Surinam and Trinidad, with emphasis on the mangrove swamps at Gandoe in Surinam and at Caroni in Trinidad. Breeding appears to be spasmodic at some colonies; the Caroni Swamp colony has bred annually since 1953, except for 1964 and 1968.

16 recoveries of 1500 birds banded at Gandoe, Surinam, show that some immatures disperse for considerable distances along the coasts. The most distant recovery is from French Guiana, about 280 miles from the natal colony; 1 bird from Trinidad was recovered in Venezuela.

The Scarlet Ibis often roosts and nests in company with most of the herons common in the 2 countries. Predators include a Water Rat (Nectomys), and possibly the Greater Ani (Crotophaga major), the Long-winged Harrier (Circus buffoni), and the Yellow-headed Caracara (Milvago chimachima). The Scarlet Ibis was hunted regularly prior to the recent passage of protective legislation in both countries. The food of the ibis includes crabs, mollusks, insect larvae, and fish. During the breeding season adults move from saltwater areas to freshwater marshes for foraging.

The Scarlet Ibis breeds in the rainy season, but nesting often covers a lengthy period and is not definitely triggered by the onset of heavy rains.

The breeding site is often shifted to a new locality, usually within a few hundred yards of the old; but circumstances suggest that they may have moved one year to a site 40 miles away.

The nests, situated in mangroves, vary in height from a few feet up to 40 feet. They consist of dry mangrove twigs with fresh leaves added on top. They last one season. Though the Scarlet Ibis often nests in company with various heron species, each species tends to group its nests on separate branches. The colony keeps together, 2500 nests being counted in 1 5-acre area in Trinidad.

The eggs are rather variable in appearance. Clutch size is usually 2 in Surinam, 3 in Trinidad, but the third egg rarely survives to hatch, and even more rarely does the third chick survive. The incubation period is about 23 d. Nestlings begin to climb about the trees at between 2 and 3 wk of age. They can fly when about 4 wk old, but probably do not do so until their 6th week.

Molt into the adult plumage may begin as early as the 5th month after hatching, and is complete when the young bird is about 1 yr old. Captive birds, deprived of carotenoids, fade to a dull pink. Various experiments appear to indicate that the Scarlet Ibis is not conspecific with the White Ibis (Eudocimus albus).

During the day Scarlet Ibises disperse in flocks to feed on mud flats and in mangrove forests. In the evening they assemble at a communal roost.

The history of hunting and conservation measures in the 2 countries is outlined. In Surinam, indiscriminate hunting took place until a 1954 game law protected the Scarlet Ibis. In addition 2 of the colonies are now in nature reserves. In Trinidad, hunting prevented breeding until 1953, when the colony was protected as part of a sanctuary, prohibiting unauthorized entry. In 1965 the Scarlet Ibis became fully protected, and is now Trinidad’s national bird, being an important tourist attraction.

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