50 ORNITHOLOaiCAL EXPLOliATIONS. 



Dr. Dybowski's mistakes are more serious. In the article in Oruith. 

 Centrbl., 1883, he says positively : " During the further development of 

 the moult the entire fore part of the bill scales ofl' and assumes a dark 

 color; the entire head becomes covered with black feathers, and the iris 

 becomes blackish brown." And to strengthen his assertion he adds in 

 a foot- note in this«very place: '' In my collection all these stages of moult 

 are represented by splendid specimens."* 



Nevertheless, this startling discovery of the shedding of the anterior 

 part of the bill, too, is not at all based on facts, being a mere supposi- 

 tion, young birds having been mistaken for adults. Dr. Dybowski him- 

 self has afterwards become doubtful about this point, which, at first, was 

 asserted with so great positiveness. His doubts are expressed thus in the 

 Bull. iSoc. Zool. France, 1883, p. 349 : " I am convinced that the worn 

 bill cannot obtain the form it has in spring without having first changed 

 its entire superficial sheath. Therefore, although I do not possess such a 

 sheath, I persist in my conviction that the bill is wholly shed,"t (italics 

 mine). What has become of the " splendid specimens of all the stages 

 of shedding"? It is, then, clear that the "discovery" is not founded 

 upon observation but upon a "conviction." The mistake rests upon the 

 circumstance that he got young birds, some with light and others with 

 dark colored undersides ; the latter he took for adults, not taking into 

 account that the former were obtained in November (B. S. Z. F., 1883, 

 p. 348) while the latter were taken later in winter and spring (Orn. 

 Centrbl., 1882, p. 28). 



The we;ir and tear of the anterior part of the bill is overcome and 

 remedied by the same process as in other birds, the external horny 

 layers flaking off irregularly, substituted by the successive growth of 

 the underlying ones. There is no need of assuming a regular shed- 

 ding of that part, and most certainly it does not take place ; conclu- 

 sive evidence, besides, is furnished by No. 92920 (j^l. i, fig. 2). 



The statement of Dr. Dybowski that the iris of the adults changes 

 from whitish to blackish brown is a result of the same confusion of the 

 adults and young, and so is the assertion that the color of the whole 

 bill of the adults is dark in winter. 



"Ini wniteren Verlauf der Mauser scLiilt sicli der ganze vordere Theil des Schnabels 

 und bekommt eine duukle Farbe ; der gauze Kopf bedeckt sich mit schwarzen Federn 

 uud die Iris wird schwarzbraun. lu rueiner Collection siud alle diese Mauser-Stadien 

 durch pract voile Exemplare repriisentirt. {L. c, p. 40.) 



t Je suis persuad6 que le bee us^, ne peut parvenira sa forme de priutemps qu'aprfes 

 avoir cliaug6 eu entier son fourreau super Aiusi done, quoique je ne poss^de 



pas de fourreaux pareil, je persiste dans uja conviction c^ue Je bee mue eu entier, 



