April, 1886.] 
OOLOGY. 
J. PARKER NORRIS, Editor. 
The Editor assumes no responsibility for those ur- 
ticles which have the names of the writer attached. 

Advance of the Science of Oology. 
In turning over the pages of the North Ameri- 
etn Odlogy, (A857,) one cannot fail to notice the 
great advance that has been made in the science 
of Odlogy since Dr. Brewer published his book. 
Apart from the fact that many species have since 
been added to our fauna since that date, the eggs 
of many birds that were rare then, or wholiy un- 
known, have since been found in comparatively 
great numbers. Dr. Brewer probably had as fine 
a cabinet in 1857 as was to be found in this coun- 
try, for in those days the Smithsonian Institution 
had not gathered together much of its now fa- 
mous collection. And yet Dr. Brewer was unable 
to figure the egg of the Golden Eagle, (Aquila 
chrysuetus canadensis,) as he could not obtain one 
for that purpose. So also with the egg of the 
Swallow-tailed Kite, -(Alanoides forficatus), which 
he could not obtain. 
In those days also very little attention seems to 
have been given to collecting eggs in sets, with 
data. The object seems to have been to obtain as 
many eggs as possible, which exhibited some pe- 
culiarity, either in size or markings. While this 
is to a certain extent desirable, it did not make up 
for the loss of value and interest attaching to sets 
of eggs. 
Of Dr. Brewer's mistakes in his Odlogy, such as 
his figuring the egg of Buteo borealis for that of 
Astur atricapillus; Accipter cooperi for Asalon 
caumbarius; and Petrocheitonlunifrons for Tuchy- 
cinetu thilussina ; it is not necessary to speak, as 
they have all been pointed out before ; but a study 
of the work is instructive, as before stated, in 
showing the great advance made by Odlogy since 
1857. What was a creditable work then would 
not be so considered in 1886. 

The Number of Eggs Laid by the 
Red-tailed Hawk and the 
Great Horned Owl. 
In the January number, 1886, of THe ORNITH- 
OLOGIST AND ObLOGIST, the present writer stated 
that the Red-tailed Hawk (Buteo borealis), more 
commonly lays two than three eges, and doubted 
Audubon’s “four or five.’ Mr. J. W. Preston, of 
Baxter, Iowa, however reports having found a 
AND OOLOGIST. 53 
set of four eggs near that locality, on April 9th, 
1885. One of them was so badly broken that it 
could not be preserved, and Mr. Preston suggests 
that possibly it may have been laid by another 
female, which was driven from the nest by a sub- 
sequent pair of birds who owned the other three 
eggs. 
Mr. Preston further writes in answer to the 
statement in the same article, that it is doubtful 
if more than three eggs of the Great Horned Owl 
(Bubo virginianus), have ever been found in one 
nest, that he took four eggs of this bird from a 
nest on March Ist, 1881. 
old crow’s nest. 
They were laid in an 
The present writer cannot think 
otherwise, however, than that two or three are 
the ordinary number; and that these were but 
the exceptions which prove the rule in both in- 
stances. 
—_—— > 
White Eggs of the Bluebird. 
BY W. E. TREAT. 
In the spring of 1883, a pair of Bluebirds took 
up their quarters in a neighbor's bird box, and by 
the 27th of April the female had deposited five 
eggs of the ordinary color. I removed three of 
these eggs, and in an interval of two days the 
same bird commenced laying again, I say the 
same bird for I am confident it was, as I had often 
made very close examinations of her. I watched 
the nest daily, and as I looked only at the eggs 
as they lay in the nest, which was in the box, and 
this darkened the eggs somewhat so that I could 
not distinguish their true color. One day I was 
informed by a friend that they were white, and | 
immediately removed the eggs, seven in number, 
including the two blue ones I bad left there, and 
I found to my surprise that five of them were 
pure white, and were about the same size as the 
blue ones. 

[The common Bluebird (Sialia sialis), is known occasion- 
ally to lay white eggs, but there has been much dispute as 
to whether this is a common variation in their color or not. 
The typical egg of this species is well known to be of a uni- 
form light blue, and it is unusual to find eggs of varying 
shades of color in one nest. When white eggs are found 
they are all equally wanting in color in the set, and some- 
times all the eggs in one nest have only the faintest tinge of 
blue; and they appear quite white until placed on some 
pure white surface, when the faint bluish tint is manifest. 
The absence of color is, of course, owing to want of the 
ordinary coloring matter, or pigment, in the parent bird, 
but is it a constitutional defect in the particular bird in 
question, or is it the result of laying a second or third set 
of eggs? The above instance cited by Mr. Treat, would 
seem to bear out the latter. No one has ever found white 
eggs of the Robin (Merula migratoria), although spotted 
ones have been sometimes found. Albino eggs are, asa 
rule, rare; but they seem to be commoner with the Blue- 
bird than with any other species.—ED.] 
