Ardea
Official journal of the Netherlands Ornithologists' Union

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Schuchmann K.L. (1978) Allopatrische Artbildung bei der Kolibrigattung Trochilus. ARDEA 66 (4): 156-172
Allopathic speciation in the Hummingbird genus Trochilus. The endemic Jamaican hummingbird species Trochilus polytmus is differentiated into two taxonomically distinct populations. The subspecies scitulus is confined to the eastern end of the island, while the other, polytmus occurs widely over the rest of Jamaica. Both populations contact each other from Port Antonio at the northern coast along the Blue Mountains and the John Crow Mountains to the Morant River in the southern lowlands (Fig. 1). In July/August 1975 and September 1976 fieldwork was conducted at several localities on the island (Fig. 3). During this program ecological, morphological and ethological data on polytmus and scitulus were collected. For further investigations individuals of both populations were brought to Frankfurt am Main. (Germany). The present study reveals that polytmus and scitulus must be regarded as separate species because: I. preference of climatically different habitats (Fig. 2); 2. morphological differences (Table 3, 4); 3. strikingly different display (polytmus: fig. 10, 11, 12; scitulus: Fig. 13, 14, 15, 16); 4. different structure of the song and territorial call (Fig. 17, 18, 19, 20); 5. absence of definite hybrids in the contact zone. The main characteristic difference of polytmus and scitulus is the colour of the beak. In scitulus the beak is completely black, whereas in polytmus only the proximal part of the beak is red ranging to pure black at the tip. According to the findings presented here, the amount of red of the beak increases depending on the age of the individual and therefore cannot be regarded as a reliable criterion of hybridization.


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