April 1891.] 



AND OOLOGIST. 



55 



The Coloration of Eggs. 



Tlie coloration of e^iis is a subject about 

 wliich comparatively little is known, and it 

 presents questions which cannot be answered. 

 Various writers have attemi^ted to discover 

 some general system in their colors, but their 

 efforts have been crowned with little or no 

 success. Some persons have supposed, for 

 exam])le, that the colors were intended to 

 render their concealment all the more easy, 

 and while this would satisfactorily explain 

 the coloration of some, notably tlie Xiy;ht 

 Hawks, etc. (CaprimulifuUe) it would not ac- 

 count for the bright hues of others. 



Again it has been assumed that colors are 

 used to protect the eggs from the sun's rays, 

 and that therefore those which were laid in 

 holes and cavities of trees, etc., like tho.se of 

 the Woodpeckers and Owls, are perfectly uu- 

 coloied, or white. But so many notable vari- 

 ations of this rule will at once occui- to the 

 reader, as for example the eggs of the 

 ("reepers, (Certhida'.) those of the Nuthatches 

 and Tits (Pciridcn), etc., wliicli are nearly 

 always brightly colored, aud yet are also laid 

 for the most part in holes and cavities, that its 

 utter f.allacy is at once shown. 



liirds whose nests are very similar, and 

 tlieir nesting places also the same, often lay 

 totally ditYerent eggs. The most notal)le ex- 

 anii)les of this are the eggs of the Long-billed 

 Marsh Wren {Cistothorus italuslrix) and its 

 nearly allied species, the Short-billed Marsh 

 Wren (€'. xtfllurl-''). It is well known that the 

 former's eggs are among the most heavily 

 colored of any found in our country, and yet 

 those of the latter bird are pure white, and 

 entirely unmarked. Their nests and tlieir 

 location, however, are almost exactly similar. 

 The birds also closely resemble each other. 

 Why should their eggs exhibit such wonderful 

 diversity ? 



Who will say that the brilliant colors of the 

 eggs of the Ptarmigans {Layopiis) are in- 

 tended to more effectually conceal them, or 

 that those of the Canada Grouse (I)cndra(i(>iius 

 canddensix) are more easily hidden in conse- 

 quence of their bright tints? 



Again, if colors are to conceal eggs why do 

 birds so often choo.se dark colored rootlets and 

 hairs with which to line their nests ? Every- 

 one will recall the brilliant contrast jiroduced 

 by the dark lining of the nests of many 

 species and the white ground color of the 



such contrasts certainly do not conduce to 

 their more ready concealment. 



These are all cpiestions which puzzle even 

 those who have given years of study to their 

 unravelment, and yet find themselves as utterly 

 in the dark at the end of their labors as they 

 were at the commencement. 



Many mistaken ideas prevail as to the color- 

 ation of eggs. An often repeated one is that 

 in a clutch of eggs, those that are the most 

 brightly marked are laid first, and that as the 

 coloring pigment in the bird gradually be- 

 comes exhausted, those laid last will be the 

 least brightly marked. 



Now in two cases I have known this to bo 

 exactly the reverse. Let me explain. In the 

 Obnituoi.ogist and Oologist for January, 

 188!), Vol. XIV, p. 11, I described a set of 

 eggs of the Canada Grouse {Dendruijopus cana- 

 densis) laid by a bird in captivity, where the 

 collector (.Mr. Watson Bishop) marked each 

 egg in the order that they were laid as he 

 removed them; and egg No. 1 has tlie fewest 

 markings of any on it, while the spots 

 gradually increase in number and size on the 

 others, so that egg No. 13 (and last) is the 

 most heavily maiked of all. 



The other case is that of a set of two eggs 

 of the Golden Eagle (Aqnila rlirys(etos) col- 

 lected March 1, 1888, in Santa Clara County, 

 California, by Mr. H. R. Taylor. The nest 

 which contained these eggs was found on 

 February 28, 1888, and on the collector ascend- 

 ing to it he found only one egg. It was bluish- 

 white, and entirely unmarked save for one 

 small spot near the larger end. The follow- 

 ing day, M.irch 1st, he again climbed to the 

 nest and found another egg, which was the 

 most brilliantly colored, heavily marked 

 specimen of this species that I have ever seen. 



Another statement which is frequently 

 repeated I have found to be incorrect, is that 

 the grays and lavenders so frequently found 

 on eggs are produced by a reddish-brown 

 color "lying in, instead of upon the shell." I 

 (piote from Dr. Cones' Key, page 223. Now if 

 this were true one could take a file and rub 

 off the outer covering until one came to the 

 reddish color in the shell. Now this is just 

 what I have often done and yet I have never 

 come to the reddish color. Instead of that 

 the gray or lavender disappears entirely, and 

 I believe that this proves that the grays and 

 lavenders are just as sepai-ate colors as the 

 reds. 



And, by the way. how often this "reddish- 

 brown" color is found on eggs ! It occurs in 



