d.Q2 Corresfo7idetice. [October 



it in mj contribution to the 'P. Z. S.' (1SS5), by Doctor Stejneo-er in the 

 ]\\\y number of 'The Auk.' 



Dr. Stejneger asks, "Is it possible tliat Dr. Sliufeldt has overlooked the 

 jnany points in which Swallows and Swifts disagree outside of the skel- 

 eton.?" To this I can answer that I duly took into consideration all of 

 those characters, both internal and external, now generally known to us, 

 when I came to draw up mv conclusions in the 'P. Z. S.' memoir, wherein, 

 as the Doctor remarks, the skeletal characters alone appear to have swaj-ed 

 me in my decisions. I am net only conversant with the '■'•many points" of 

 difference existing between Swallows and Swifts, but am becoming more 

 convinced every day of the ^niany, many points' of structural difference ex- 

 isting between the Trochili and Cypseli. 



Further along in his criticism, when reviewing for my benefit some of 

 the more prominent difterences existing between the Swallows and Swifts, 

 as Dr. Stejneger compi-ehends their structure, he contends that "internally 

 they differ in a great number of points, but Ave shall only mention that the 

 Swifts have a sternum, while the Swallows have the manubrium bifurcate 

 and the posterior border deeply two-notched." Reading this sentence over 

 carefullv a number of times I must confess that its author does not make 

 quite clear to my mind the kind of comparison he wishes to institvite be- 

 tween the sternum of a Swift and a Swallow. No one probably will deny 

 "that the Swifts have a sternum," though many might take exception to 

 the remark that that bone was "two-notched" in the Swallows. To be 

 sure it has a J>air of notches in its xiphoidal extremity; but as generally 

 described, the two-notched sternum is seen in such forms as Picus. 



Again, Dr. Stejneger asks me in his criticism, "but what differences 

 are there in the Swifts' flight from that of the Swallows' that should have 

 caused such a remarkable modification towards the Huinming-birds.'"' 

 (p. 406). My answer to this question will also constitute a reply to the two 

 succeeding questions of my critic, as it will, I hope, still further impress 

 upon the minds of systematists the warning, already given in my 'P. Z. S.' 

 memoir, that the similarities of certain structures existing between the 

 Cypseli and Trochili are for the most part due to the modification of these 

 structures gradually brought about by the habits or actions of the forms 

 in question. Surely Dr. Stejneger would never have asked the question I 

 have first quoted from him if he had ever had the opportunity to compare 

 in nature the flights of two such birds for example as Micro^us melanoleu- 

 c/is and Tachycincta tkalassina. Many a time have I stood in the deep, 

 rocky canons of New Mexico, and seen one of the former birds pitch down 

 from its dizzy position in the air above, with a velocity that taxed the very 

 eye of the observer to follow, to its nest in the side of the precipice below; 

 check itself suddenly at its entrance ; hover for an instant, like a Hum- 

 mingbird over a flower, with its wings in rapid motion, then enter, — to 

 be gone but a moment, — when it makes its appearance again as if shot 

 from a gun, to be oft" with the swiftness of the bullet. How different is all 

 this from the flight of the pretty little Violet-green Swallow, with it slight 

 and easy motion, rarely hurried and never precipitous! 



