EGGS: 
The number of eggs in a full set is from four to six. The shell is delicate blue, varying slightly 
in shade in different specimens, and is moderately polished. "YV hen blown, the color becomes purer in 
tone than before, and the whole shell assumes a beautiful semi-transparency which disappears in a day 
or two, about the same time, the blue begins to fade, and in a few years the specimen becomes nearly 
white. Occasionally, pure white eggs are found. The average size is .84 x .64 of an inch. The longest 
egg in my possession is .87 ; the shortest, .80. The greatest short diameter is .67 ; the least is .61. 
Incubation lasts about twelve days. 
DIFFERENTIAL POINTS : 
When the eggs are tinted with blue, they may be recognized at once, as there are no others at all 
like them. The nest, when normal, may also be recognized by the description ; but if it departs from 
the common type — which it sometimes does, in cities or about dwellings — no rule can be given for its 
identification. 
REMARKS : 
The nest represented by the plate was found the first of April. It was built in an old black-walnut 
stump, in a wheatfield. The part containing the nest was sawed-off below, and split-open so as to give 
a clear side view of the structure, which was composed of blades of grass, and contained live eggs. 
The entrance to the cavity was from above, and was distant from the ground about two feet. 
The habits of the Bluebird have been so often and so accurately described, and are so familiar to 
all that it is unnecessary to go into detail here. But there is a point in the life-history of the bird I 
wish especially to mention. It is their great pugnacity and bravery. I have repeatedly known them to 
attempt to drive other birds from their homes, and generally the attempt is successful. The Red-lieaded 
Woodpecker is a frequent victim to this scheme. Having labored hard to excavate a suitable habitation, 
and about ready to begin the cares of housekeeping, they are often set upon by a pair of Bluebirds, 
and so persistent is the attack that the Woodpeckers, perhaps afraid more blood will be spilled upon 
their already scarlet heads, disgracefully retreat. The Martin and Wren are likewise tormented, but as 
often recompense them with similar proceedings. 
Some years ago, I placed a bird-box upon the house-top, which for a few seasons was occupied by a 
pair of Bluebirds. One spring they failed to appear at the usual time, and the box was taken by a 
pair of Martins. The old nest was carried out, and the new-comers were thoroughly settled in their 
quarters, when the Bluebirds returned (probably the same pair that formerly occupied the box), and at 
once commenced tearing out the intruders’ nest. But they were soon discovered, and a pitched battle 
ensued, the Bluebirds retiring as if defeated. This procedure was repeated several mornings and at 
intervals during the days. When, early one morning, being awakened by the incessant screams of the 
Martins, I hastened to the yard to see what I supposed was the final encounter; but the affray was 
over before I arrived. My father, however, was there, holding a female Martin in his hand, he having 
witnessed the whole affair. After much scolding and sparring, one of the Bluebirds clinched with the 
Martin, and both rolled together from the house-top to the pavement below, where, in deadly embrace, 
they were captured; but the Bluebird, still strong and active, slipped away. In all these engagements, 
the male Martin seemed content to encourage his mate by his vociferous screams, while both Bluebirds 
fought with equal valor. If the female Martin had received the substantial support she deserved from 
her genteel spouse, the result of the engagement might have been more satisfactory to her, and much 
more creditable to her companion. 
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