178 



ORNITHOLOGIST 



[Vol. 7-No. 23 



circle. The wall of the nest is generally 

 thicker at one end of the ellipse than else- 

 where. 



Six of the seven nests contained three 

 eggs each, the other hiit two. Dr. Coojjer 

 and Capt. Bendire, the only naturalists who 

 appear to have found the nest of this spe- 

 cies before nie, never found more than two 

 eggs in a set. Dr. Cooper found a single 

 nest near Fort Mojave, on April 27. Capt. 

 Bendire, in the season of 1872, found four- 

 teen nests in the vicinity of Tucson, Ari- 

 zona, and not one contained more than two 

 eggs, "and in three instances the nest con- 

 tained but a single egg and the bird hard 

 setting upon that." Some of the nests he 

 found saddled upon a limb after the man- 

 ner of other flycatchers, some between 

 dead bark and the trunk of the tree, and 

 again he found the nest fixed in between a 

 lot of young sprouts of a mesquite tree. 

 The nests found by him were obtained be- 

 tween May 16 and June 24. 



Capt. Beodire, in a letter to me regarding 

 this bird, in speaking of our entirely dif- 

 ferent observations regarding the number 

 of eggs laid by it, gives the following ex- 

 planation, and I may add that his views 

 seem most reasonable and are undoubtedly 

 correct He says : " The small number 

 found by me is unquestionably due to the 

 fact that in Southern Arizona they raise 

 two and perhaps three broods, while in 

 California, where we found them, they 

 raise but one. This I know applies to such 

 Sf)ecies as the Icteria inrens lonf/lcat«hi 

 and others also whose range in Summer is 

 extensive. Here (Fort Walla Walla) this 

 species (Long-tailed Chat) always lay four 

 eggs, while in Ai-izona three is the rale, 

 and the latter are considerably smaller. 

 Why the latter should hold good, too. I am 

 not so sure about, but I can readily see 

 why this .si^ecie lays fewer eggs to the set ; 

 raising two or three broods a season fully 

 makes up for this." 



Of twenty eggs obtained by me I took 

 measurements of fifteen, five havuig been 



sent away before I had an opportiinity of 

 measuring them. The fifteen measure as 

 follows: — set (1). .90x64, .92x.62, and 

 .89x.62: set (2), .!)5x.67i .92x.67, and 

 98x70 ; set (3), .90x.65, .90x.64, and.89x.65, 

 set (4), .90x.6.5, .87x.6.5, and .90x.63 : set 

 (.5), 1.03X.63, .95X.62, and .94x,65. A set 

 of three which I sent T. G. Gentry and 

 whicli he figures in Part XXV of his work 

 on Nests and Eggs,' gives the following 

 measiu'ements as determined by him : 

 .94x.G9, .94x68, and .93x.68. The average 

 of the first fifteen is found to be .923x.646 ; 

 or of the eighteen. .925x.652. Baird, 

 Brewer, and Ridgway's North American 

 birds gives .90x.60, being smaller than any 

 one obtained by me. It is not stated where 

 this egg was obtained, yet I presume it is 

 either a Fort Mojave or an Arizona egg. If 

 so, its small size when comjjared with more 

 northern specimens confirms Capt. Ben- 

 dire's conjecture that, when the usual set 

 of eggs is fewer in the Southern than in 

 the Northern portion of any species' breed- 

 ing range, the eggs are also smallei-. May 

 it not be true that the individuals of -dwy 

 given species which go farthest North to 

 breed, average a trifle larger and more ro- 

 bust than the weaker brothers and sisters 

 that stav' at home ? It seems evident that 

 those individuals which put the greatest 

 number of miles between thei)' Winter 

 home and their breeding ground, must nec- 

 essarily be the stronger ones ; the fatigues 

 of travel, the changes of climate, and other 

 mollifying influences demanding and de- 

 velo2)ing a hardier variety. And may not 

 the larger size of the Northern egg permit 

 a more prolonged endjryotic developuicnt, 

 resulting in a chick of greater size and 

 greater strength, — one better able to cope 

 witli its less favorable environment? I sug- 

 gest this merely as a possible, and what- 

 appears to me a reasonable, solution of the 

 question. 



Regarding the singing abilities of the 



*IIIustrationB of Nests and Eggs of Birds of the ITnited 

 States, with Text ; By Thos. G. Gentry. Philadelphia : J. 

 A. Wagenseller, Publisher. 



