BIRDS OF PORTO RICO. 



PHYSIOGRAPHY OF PORTO RICO. 



Approximately 100 miles long by 40 broad, Porto Rico, though 

 the smallest of the Greater Antilles, possesses considerable diversity 

 of surface. From Mayagiiez to Humacao extends a mountain chain 

 known in the west as the Cordillera Central and east of Aibonito 

 as the Sierra de Cayey. Northeast of the latter runs the Sierra de 

 Luquillo, rising in El Yunque to 3,406 feet above sea level, the 

 highest point on the island. From this central divide the descent 

 to the coast is abrupt and much broken by series of hills cut by deep 

 ravines. As the range is nearer the south coast the larger streams 

 flow to the north. A low divide separates the northeastern moun- 

 tain mass from the main range, and others, higher, offer passage 

 across the island at several points. 



The coastal region is formed by a narrow plain extending around 

 the island, though in a few places the hills approach the sea abruptly. 

 In this plain, conical limestone hills rising to sharp points are fre- 

 quent, and inland is found a rough limestone foothill region. Man- 

 grove swamps and shallow lagoons, many of which have been drained 

 of late years, are found near the mouths of rivers on the north and 

 west coasts, and at Guanica is a considerable body of fresh water 

 with surrounding marshes. 



Governed by the prevailing northeast trade winds, rainfall varies 

 greatly in different localities. For the entire island the annual 

 average precipitation amounts to 77.3 inches. The south coast 

 is relatively dry, the greatest precipitation occurring on the north 

 side. The maximum volume of rain falls in the northeast on El 

 Yunque and about its base, where the annual average is 135 (maxi- 

 mum 169) inches. The northern slopes of the central mountain range 

 as a whole secure the greatest quantity. Along the northwest coasi; 

 from Isabela to Camuy is an area of small precipitation, at times 

 very dry, while the south coast from Cabo Rojo to Guayama is 

 almost universally so, the annual average being 40 inches or less. 

 The rainy and dry seasons are not well defined, rains occurring 

 throughout the year. The minimum rainfall is in February, while 

 the maximum occurs from May to November, varying with the 

 locality. 



Vieques and Culebra Islands are comparatively low, with many 

 rounded hills. Lagoons are found near the sea, though they 1 are 

 frequently dry. The general appearance of the islands is that of 

 the south coast of Porto Rico. Desecheo Island in Mona Passage is 

 smaller, and rises in two conical hills from the sea to an altitude of 

 about 400 feet. A rough path leads up and down over the rocks 

 above the beach, but inland the brush is almost impassable. Mona 

 Island, as described by Bowdish (MS.), is 7 miles long by 3 or 4 

 wide and is rather barren. It slopes gradually from the higher north 



