®fjj> Harbler I9 



day by day, to fussy Brewer Blackbirds among the plum bushes, became 

 gradually crystalized into curiosity. When this had become formative, it 

 became but the work of a moment to discover a dozen or more of nests of 

 the Brewer Blackbird among the goose-berries. Herein was proven the 

 value of enjoying masses of material for generalization. It is remarkable 

 how slowly the mind often moves in its inductions. I must have examined 

 six or eight nests, or more, each with its full complement of eggs, or more ; 

 before there burst upon me, all at once, the full realization of somewhat that 

 I had long and feebly guessed-at ; namely, that the Brewer Blackbird is, by 

 habit, mutually parasitic ! A number of the nests found, on this broad 

 plum-bush slope, contained from six eggs to seven. In every case where the 

 eo-o-s were more in number than five the presence of two distinct types of 

 eggs in the same nest became well apparent. With new zest for search, I 

 now re-traversed the entire colony : finding new nests ; re-examining those 

 already found ; and making many comparisons. The results afforded sub- 

 stantial proof of the validity of the law which I believed myself to have 

 discovered. 



And they also explained the mystery that had long hovered over 

 past findings ; in regions very far away. They made plain the cause of the 

 several "sets" of seven found in Northern Minnesota. And they explained 

 the most wonderful, the most beautiful, mystery of all : a most marvelous 

 " freak" set of eggs found in that colony on the slopes of Sundance Moun- 

 tain. At the highest point in the colony I had flushed a peculiarly anxious 

 sitting bird from a " set " of two eggs. At these I had stared long and 

 wonderingly. I had seen many odd eggs of the Brewer Blackbird before ; 

 but none, before, one-half so odd as these. 



Many egg-students, — for there ARE egg-students, — are well aware that, 

 with community-breeding birds, there is usually a great diversity in colors, 

 sizes and shapes, of eggs. This fact had previously been the cause of my 

 ignoring the great contrasts to be found in many large "sets" of eggs of this 

 most freakish of all American Blackbirds. But, with the newly-discovered 

 habit to guide me, I now knew why, in the one nest. I should find one egg 

 of as delicate a blue, (as to ground-color), as any egg of Cuckoo or glossy 

 Ibis ; and the other, as rich a (mottled) sepia-tint. I never saw two eggs 

 more utterly unlike ; their likeness being one of size, merely. Risking the 

 chance of robbery by some marauding Magpie, I had left my wonderful 

 freak set of two ; to see whether the laying mother might not bring-forth a 

 red egg, next ; and a yellow one, perchance, the fourth time. But just so 

 soon as it dawned upon me that those two eggs had been laid by different 

 birds, I stalked across the Sundance Valley ; climbed the steep lower-slope; 

 flushed my sitting bird ; and appropriated the two precious eggs. They 

 proved to be incubated, — both of them, — and in varying degrees. 



