BLUE OR METALLIC BLUE 503 
Nest: In holes, excavations, natural cavities, etc.; made of grasses and 
straw ; thickly lined with feathers. 
Eggs: 4to7; pure white. Size 0.75 X 0.53. 
EaRzy in July the Tree Swallows begin to gather in 
flocks; and, from that time until they start on their 
southern migration, innumerable multitudes of them are 
to be seen flying over the open country. They sit in 
crowds on telegraph wires or any available perch, gather- 
ing late in the afternoon and, when near water, circling 
over it in an endless game of “ Follow the Leader.” 
They dip daintily, each one in turn, rise, circle, and dip 
again, just brushing the surface with a light splashing, 
until the shadows of evening fall and it is too dark to 
watch them longer. In almost any section of the United 
States they are the swallows best known, at least to 
city folk, and are, I believe, the ones whose return 
migration has been celebrated in the old song. 
They still adhere to the old habits of nesting in hollow 
trees, only a small portion having been induced to try 
the boxes put up for them by bird-lovers. Undoubtedly 
they will in time accept this substitute and become as 
changed in their environment as are the eave and barn 
swallows ; but no one can wonder that they love the 
forest best and are loath to leave it. At Lake Tahoe we 
found them nesting in the old piles of the deserted pier, 
in company with the Brewer blackbirds. They entered 
the nesting cavities, which were usually two to five feet 
above the water, by a knot-hole or crevice in the wood. 
One nest whose brood I watched develop was so filled 
with feathers that they waved in the doorway, calling 
