AN ECOLOGICAL STUDY OF CARTAGENA LAGOON, PORTO RICO, WITH SPECIAL REFERENCE TO THE BIRDS

Abstract

A total of 105 species of birds are found at Cartagena Lagoon and its immediate vicinity. Of these, 42 are migrants from North America. Another 42 species breed there either regularly or occasionally. Two of these (Progne dominicensis and Vircosylva c. calidris) breed in Porto Rico but winter in South America, and it is possible that a third species (Himantopus mexicanus) does likewise. Twenty-one species come to the lagoon only to feed, though breeding in other parts of the Island. An average of 36 species of birds per day were recorded at the lagoon. The largest day's list was 48 species on April 11, 1924, and the smallest 26 species on August 13, 1924 (when the lagoon was nearly dry). The largest list in t he fall was 45 species on September 30, 1924. Of the 42 species of birds breeding at or in the immediate vicinity of the lagoon, 19 might be called typical lagoon species. Nine of these are entirely dependent upon the marsh for food and shelter, while 10 visit it primarily for food. Three of the ten, namely, Poecilonetta b. bahamensis, Butorides virescens maculatus and Oxyechus vociferus rubidus, visit it because they show a preference for marsh conditions and aquatic food. The other seven occur at the lagoon because of the abundance of food found there rather than on account of any special preference for marsh conditions or aquatic food. In this class I would include Zenaida zenaida lucida, Chaemepelia passerina trochila, Crotophaga ani, Tyrannus d. dominicensis, Agelaius xanthomus, Holoquiscalus niger brachypterus and Dendroica petechia bartholomica. Although some of these birds, namely, Zenaida zenaida lucida, Holoquiscalus n. brachypterus and Dendroica p. bartholomica, nest more or less regularly in the marsh, there are no birds which appear to visit the marsh primarily for shelter. Of the 9 species which are entirely dependant upon the marsh for food and shelter, Colymbus d. dominicus is almost entirely restricted to the cat-tail zone, and Podilymbus podiceps antillarum to the open-water association. Frismatura alleni prefers the sedge and cat-tail zones for nesting. Ixobrychus e. exilis is entirely restricted to the cat-tails for breeding. Porzana flaviventris is found chiefly among the cat-tails and sedges, but its nesting habits are unknown. Gallinula chloropus portoricensis and Fulica caribaea major are chiefly birds of the cat-tail, sedge and grass associations, while Ionornis martinicus prefers the cat-tails for nesting. Himantopus mexicanus prefers the grass association, but it is very adaptable, and establishes it self in almost any zone when it is molested in another.