614 STEECOEAEIUS PARASITICUS, PARASITIC JAEGEE. 



to white : so that the bird tends at once to assume the bicolor plumage of the adults 

 without going through the dusky-unicolor stage. This is one of the perplexing facts 

 ■we encounter in studying the question. We tiud that the very immature plumage of 

 the young birds in August can be traced through one series directly into the fusoo- 

 uuicolor stage ; through another into a state which seems to jiass directly into that of 

 the normally-colored, fully adult bird. Various explanatious have been offered to ac- 

 count for the dusky stage of plumage. Some authors consider it as a sexual feature, 

 regarding it as the normal adult plumage of one sex (according to some the male ; to 

 others the female!) Others look upon it as a seasonal feature, attained at a certain 

 time in each year, and regularly recurring each successive season. Still others, again, 

 consider it as a distinct I'arkty, accidental and irregular according to some, permauent 

 according to others. With regard to the question of the seiuuJ nature of this state, I 

 think the evidence is decidedly against such a belief. The very fact that those authors 

 ■who Qontend for this opinion difter as to wMch sex — some affirming that they found 

 testicles and others that they saw ovaries in the dusky birds they dissected— seems to 

 me conclusive evidence that the state of plumago in question is common to both sexes. 

 I cannot admit the hypothesis that this state constitutes a permanent or accideutal 

 variety. I do not think it possible that normally-colored adult birds can have young 

 which attain at once this dusky state and retain it during their lives ; still less that 

 they can transmit their abnormal characters to their offspring, as would be neces- 

 sary to constitute a permauent variety. The supposition that it is a purely accidental 

 variety — i. e., that certain individuals, without any cause, by a freak of nature as it 

 were, become thus colored and remain so for their whole lives — seems still less worthy 

 of credence. Examples of this condition of plumage are too numerous, and bear alto- 

 gether too definite relations with certain other stages, uot to be brought about by aud 

 dependent upon some definite law. The preceding suppositions being untenable, I 

 think there can be no reasonable doubt as to the true character of the stage of plum- 

 age in question, from the amount of evidence which we have tending to prove it de- 

 pendent upon age and season. I do not hesitate, therefore, to express the decided 

 opinion that this unicolor state is a transient, immature stage of plumage, perfectly 

 normal, and universal, or nearly so, independently of sex, which every Jager — or at 

 least the great majority of individuals — passes through in its progress toward ma- 

 turity, after leaving the plumage it first assumed, and before it arrives at the plumage 

 ■which is indicative of maturity. The ouly question is, exactly what age this plumage 

 is indicative of, and whether, after once having attained to this fully mature condition, 

 the adults do or do not return to this unicolor state at certain season of each year. 

 lly opinion is, that it supervenes, ordinarily at least, directly upon the disappearance of 

 the rufous, which is characteristic of the very young bird, and therefore is probably as- 

 sumed after the first moult and retained until the second. I do not think it prohaWe 

 that the adults which have passed through this state ever return to it ; for, as remarked 

 uuder head of S. pomatorhintis, we nearly always find these unicolor birds possessed of 

 of smaller, weaker bills, and slenderer, generally particolored, feet ; all of which char- 

 acters are invariably indicative of the immature bird. 



Synonymy. — It is difficult, perhaps impossible, to say whether the names and descrip- 

 tions of authors before 1800 really refer to this species or to the buffoni. It is most 

 probable, however, that the former is really the species meant, both because it is the 

 most abundant and well known, and because Retzius, in his edition of the Fn. Snec. 

 (in which work the species is definitely settled by giving the exact length of the cen- 

 tral rectrices *), cites as synonymous nearly all the names and descriptions in question. 

 He errs, however, in adducing S. longicaudatus, Brisson, which is the huffoni. Catha- 

 racta parasitica of Briinnich and the Larus parasiticus of Linu£eus, Gmelin, and Latham 

 in all probability really refer to this species, and it is from the former of these authors 

 that the specific name is accepted. But Lams parasiticus of Latham (1790) may have 

 been based upon the long tailed species, for the reason that the length of his bird is 

 given as 21 inches — a dimension never attained by parasiticus. The synonyms of the 

 two species are indiscriminately cited. 



The Catharacta coprotheres of Briinnich is this species in its fusco-unicolor stage. On 

 its very first introduction, in 1764, Briinnich himself doubts its validity as a species, 

 and says of it: "An precedenti— parasiticus — seom vel specie diversa" ? Yet down to the 

 present time it has always been held by some authors as distinct. Thus, in 18GG, Bona- 

 parte gives a variety (coprotheres), and still later, in 1860, Des Murs presents a species 

 {Lesttis coprotha-es). 



An early, detailed, and unmistakable description of this species is that of Brisson, in 

 17(10, who gives an accurate account of it under the mononomial appellation sterco- 

 rarius. The species serves as the type of his genus. 



The Stircorarius crepidatus of Vieillot (ut supril) is based upon this species, although 

 his specific name is taken from Gmelin and Latham, who probably based their de- 

 scripl ions of crepidatus upon the young pomatorhinus. So, also, the Lestris orepidaia of 



* Fn. Suec. p. 180 : " Ecctrices 6, C (i. e., the central pair) Cisteris 4 poll, longiorea." 



