74 MATERIAL 
woodland birds generally employ twigs, rootlets, bark, leaves, mosses, 
etc., while field-inhabiting species, as a rule, use chiefly dried grasses. 
It follows, therefore, that a change in the nature of a bird’s haunts 
often causes more or less variation in the character of its nesting mate- 
rial. In the North, for example, the Acadian Flycatcher builds its nest 
of plant-stems, grasses, and dried blossoms, but in Florida it uses the 
Spanish or Tillandsia ‘moss,’ a material, by the way, which enters into 
the nests of many birds. In the East, Night Herons, building in trees, 
use sticks; in the West, where they nest in marshes, the nest is composed 
of reeds. There are many similar instances. 
A familiar case of local variation, due to change in environment, 
is furnished by the Baltimore Oriole, which gathers string, worsteds, 
etc., in place of plant fibers; and experimenters have tried to determine 
the bird’s choice of colors by supplying it with worsteds of varied hues, 
without, however, other result than a demonstration of range in choice 
among different individuals, since some selected gay and others dull 
colors. 
The use by birds of rags, paper, horse-hair, etc., also clearly illus- 
trates the influence of civilization on the bird’s selection of material 
with which to build a nest. 
The necessity for concealment is, in some cases, a potent influence 
in the choice of nesting material. What is generally spoken of as ‘nest 
decoration,’ if it have any significance, is assuredly not designed to 
make the nest conspicuous through display, but inconspicuous by 
matching it with its surroundings. The lichen-covered nests of the 
Wood Pewee, Blue-gray Gnatcatcher, and Hummingbird are examples 
of this class. 
The Great-crested Flycatcher introduces a bit of cast-off snake- 
skin into its nest, it has been said, to serve the purpose of a scare-crow. 
The explanation is important if true but lacks evidence to support it. 
The student should try to observe the methods employed by birds 
in gathering and carrying the material for their nests, noting, for 
example, Robins, Barn and Eave Swallows picking up billfuls of mud, 
a Chimney Swift breaking off dead twigs with bill or feet, a Humming- 
bird collecting lichens from a tree-trunk, an Oriole tugging at a plant 
fiber, etc. 
Construction.—Then follows a study of nest-construction, from the 
simple method of the Skimmer which by squatting low and turning 
around again and again hollows a nest in the sand, to the more complex 
activities of Swallows, Swifts and Orioles, which respectively exhibit 
the arts of the mason, joiner and weaver. Herrick’s detailed and, so far 
as I am aware, unique study of a pair of Robins while nest-building, 
should be read in this connection. The work may be performed by one 
or both sexes. In the former case the female is usually the builder when 
the male may assist by bringing material. The nest may be completed 
in a day and occupied at once, or a longer time may be required and it 
may apparently be deserted for days after its completion. The weather, 
