14 VLLINOLS AUDUBON AB UME. 
The other branch of the woodpeckers’ evolutionary tree contains 
species such as the Hairy Woodpecker, whose niche centers upon tree 
trunks and large limbs, and the nearly identical but proportionally smaller 
Downy Woodpecker, which occupies a niche on smaller branches and 
twigs. The Yellow-bellied Sapsucker has a specialized tongue with a 
brush-like tip, thus enabling it to feed effectively on sap oozing from holes 
its drills in trees. Finally, at the top of the evolutionary branch, one finds 
the peculiar three-toed woodpckers (Picoides). Of course, not all these 
woodpecker species occupy the same habitats. Some species are distribu- 
tionally separated. 
The fruit-eating behavior of tanagers in Trinidad’s mountainous Nor- 
thern Range offers additional examples of niche exploitation and its role 
in governing bird distribution within a given habitat. Of the island’s three 
attractive Tangara species, the Speckled Tanager is mainly a forest 
dwelling bird. While remaining in a perched position, it picks fruit and 
eats it whole. The Bay-headed Tanager also eats fruit, but it pecks 
pieces and sometimes while airborne in manikin-fashion, takes fruit. Fi- 
nally, the Turquoise Tanager often occurs in flocks. This species also 
erches to pick fruit and seems prone to pick pieces out of large fruits. 
eee ‘Tanagers also mandibulate fruit in an apparent effort to re- 
duce its size or eliminate seeds before swallowing it. Mistletoe fruit forms 
a larger proportion of this tanager’s diet than in other species. 
These examples deal only with a few aspects of the complex subject 
of niche requirments of birds. Many important additional factors also 
can be involved in determining a bird’s niche requirements. Nonetheless, 
even cursory observations of niche requirments offer curious birders an 
opportunity to derive added pleasure from their hobby. Why merely 
look at a bird when you can attempt to understand its ecological role? 
Of course, there are many instances when general birding activities will 
not enable you to gain insights into the fascinating world of ecological 
niche. But frequently cursory observations are adequate to hint at an 
animal’s niche requiremnts. So sharpen your observation skills and ask 
yourself probing questions regarding the activities of the birds you see. 
You may discover something new to science as well as enhance the re- 
wards of your birding activities. 
REFERENCES 
Allen, G. M. 
1962 Birds and their Attributes. Dover Publications, Inc., New 
Yorks Nave 
Griscom, L. and A. Sprunt, Jr. 
1957 The Warblers of America. Devin-Adair Co., New York, N.Y. 
bacien |) 
1971 Ecological Isolation in Birds. Harvard University Press, 
Cambridge, Mass. 
Snow, B.K. and D.W. Snow 
1971 The Feeding Ecology of Tanagers and Honeycreepers in 
Trimdad. Auk, 88:291-322. 
