1916 J Huxley, Bird-watching and Biological Science. 265 



and the way in which facts under various headings can be sum- 

 marized as they accumulate. 



I intend to go on collecting data on courtship of birds for a num- 

 ber of years, and will be very grateful if other watchers will send me 

 facts. Of course fragmentary details are not of much value, and 

 in the case of diary notes made on the spot, a short summary under 

 various headings will enormously reduce the labor involved in 

 digesting the notes. 



Before I close I would like to mention a few problems that have 

 occurred to me during the short time I have been in America — 

 problems that would be far better attacked by a number of watchers. 



In the first place the whole conception of mutual courtship is 

 new, and has to be worked out in detail. As definite problems here, 

 I would suggest the following. 



(1) What is the course of events in the Meadowlark, a bird 

 with marked protective coloration above, and with its tail showing 

 recognition marks, but with brilliant and probably sexual colora- 

 tion on the breast, which is equally developed in both sexes? 



(2) What is the meaning of the duets which only a few weeks 

 ago I heard performed by the Barred Owl {Strix varia)? One per- 

 former gave a variation of the regular hooting, while the other 

 rendered the same musical phrase, but in tones of demoniacal 

 laughter, and alternating its notes with those of its mate. Bendire 

 has a note on this remarkable habit. 



In what was probably the Short-eared Owl I have seen remark- 

 able " bowing duets," the birds curtseying to each other in exagger- 

 ated fashion. In the Dabchick, the vocal duet is the most promi- 

 nent feature of courtship, taking the place of the head-shaking 

 of the Great Crested Grebe. 



(3) In a single group, like the Sparrows, we find very different 

 gradations of sexual coloration. What is the difference between 

 the courtship of such species as the Chipping Sparrow, the Lark 

 Sparrow, the English Sparrow, and the White-throated Sparrow? 

 In the first two, both sexes are alike, but the first species is sober- 

 colored, the second distinctly gay; the last two show sexual 

 dimorphism in varying degree. Still other species could equally 

 well be chosen for the study. 



(4) In the Woodpeckers, both sexes are usually fairly brilliant, 



