kind of bird group under consideration. 

 Certainly, more information is needed, 

 particularly concerning the dependence of 

 rare or endangered species on specific 

 community types. 



9.9 MANGROVES AS WINTER HABITAT FOR NORTH 

 AMERICAN MIGRANT LAND BIRDS 



An interesting observation based on 

 the data in this chapter is the seemingly 

 important role that mangrove ecosystems 

 play in providing wintering habitat for 

 migrants of North American origin. Lack 

 and Lack (1972) studied the wintering 

 warbler community in Jamaica. In four 

 natural habitats including mangrove 

 forest, lowland dry limestone forest, mid- 

 level wet limestone forest, and montane 

 cloud forest, a total of 174, 131, 61, and 

 49 warblers (individuals) were seen, 

 respectively. When computed on a per hour 

 of observation basis, the difference is 

 more striking with 22 warblers per hour 

 seen in mangroves and only 1, 2, and 1 

 seen in the other forest habitats, respec- 

 tively. For all passerines considered 

 together, 26 passerines/hour were seen in 

 mangroves with 5, 13, and 3 respectively 

 in the other forest habitats. On a 



species basis only 9 were recorded from 

 mangroves whereas 19, 13, and 16 species, 

 respectively, were seen in the other habi- 

 tats. This large number of species from 

 the other habitats appears to result from 

 the sighting of rare species after many 

 hours of observation. Only 9 hours were 

 spent by Lack and Lack (1972) in the man- 

 groves whereas between 30 and 86 hours 

 were spent in other habitats. More time 

 in the mangrove zone would have undoubted- 

 ly resulted in more species (and in- 

 dividuals) observed (Preston 1979). 



Hutto (1980) presented extensive data 

 concerning the composition of migratory 

 land bird communities in Mexico in winter 

 for 13 habitat types. Mangrove areas 

 tended to have more migrant species than 

 most natural habitats (except gallery 

 forests) and also had a greater density of 

 individuals than other habitats (again 

 except for gallery forests). In both Lack 

 and Lack's and Hutto's studies, disturbed 

 and edge habitats had the highest number 

 of species and greatest density of 

 individuals. The percentage of the 

 avifauna community composed of migrants 

 was highest in mangrove habitats, however. 

 From this we can infer the importance of 

 mangroves in the maintenance of North 

 American migrant land birds. 



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