Birds of Celebes: Falconidae. 
71 
another'); but, when some of these species by reason of overcrowding, a storm, 
or other cause, are transported to m fresh locality where the conditions of 
existence are changed, the original, fixed coloration becomes disturbed — if 
there was originally a useful jDurpose in it, that purpose is noAV removed, — 
variability has free play for the time, and the amount of variation is made 
greater and more complicated by the interbreeding of the changing individuals. 
On these grounds the Celebesian Hawk-eagle and Honey-buzzard should be 
regarded as ancient forms, the variable birds of Borneo, etc. which have not 
yet settled down into a fixed type of plumage of their own, as of more recent 
origin. Leaving out of the discussion Pernis tweeddalei of Malacca which is only 
knoAvn in three or four specimens, the only remaining species of Pernis is our 
own Pernis apivorus — very variable and therefore, also recent. Spizaetus, 
however, has developed into a number of local species elsewhere than Celebes 
viz. the Indian Region, Africa, S. America. Let it be remembered, that Celebes, 
as is shown by some of its mammals as well as by some of its birds, is an 
ancient land, zoologically speaking, and that neither Pernis nor Spizaetus (ex- 
cept in the aberrant S. gurneyi) pass into the still more ancient Australian Re- 
gion, and it will be seen that P. celehensis S. lanceolatus have some claim 
to be regarded as the most ancient members of their genera. 
(C) One of the most convincing arguments made use of by Charles Dar- 
win in tracing the descent of domestic Pigeons from the Blue Rock Pigeon 
( Columha livia) was drawn from the occasional reversion, partial or nearly 
complete, of the former to the plumage of the Blue Rock. If the variable 
Spizaetus limnaetus and Pernis ptilonorliynchus are descended from specimens of 
^S'. lanceolatus and P. celebensis which have flown across from Celebes to Borneo, 
or the Philippines and further, similar cases of reversion should be found. JSToav, 
in his Valkvogels Ned. Ind. Schlegel portrays nine specimens of the variable 
Spizaetus limnaetus (called by him >S'. cirratus) and six of Pernis ptilonorhynckus 
(here called cristatus: pis. VI- VIII and XXV, XXVI), and among them some fairly 
good matches to the two forms of Celebes may be seen. About four specimens 
of a Honey-buzzard called Pernis tiveeddalei, Hume, have been described from 
Malacca and Sumatra; it bears much resemblance to Pernis celebensis, and it seems 
very doubtful if they are more than individual variations of the variable P. jotilono- 
rhynchus, since that bird lives not only on both sides of, but also in the same 
localities as the supposed distinct form (cf. Hume 6, and Str. F. 1887, X pL, 
p. 513; Schlegel a I, and Mus. P.-B. Pernes 1862, 2; SchL & S. Mull., Verb. 
Natuurk. Comm. 1839 — 44, 49, pL; Kelham, Ibis 1881, 369; Gurney 5, 7). The 
little known Spizaetus philippe7isis, which seems to be much like the Celebesian 
Hawk-eagle (see Walden, Tr. Z. S. 1875, IX, pi. XXIV), is not unlikely to prove 
1) As an exception the extinct Solitaire fPezophaps) of Rodriguez must be mentioned (see: Newton, 
Diet. B. “Solitaire”). This large bird was most variable in structure and colour. It used evidently to get 
much knocked about in fighting. The male Ruff, another great fighter, is probable the most variable bird known. 
See remarks in Introduction on inherited mutilations of feathers, etc. 
