4 
Birds of Celebes: Falconidae. 
dress assumed in the nest itself. Longitudinal streaks on the feathers of birds appear 
to represent a more original, less highly differentiated plumage than do cross-bars; 
this is shown by the fact that almost all birds of prey, which when adult acquire a 
cross-barred under-side, have this region streaked or drop-marked when immature. 
If Gurney’s view, that the pale, streaked specimens of Spilornis are in the 
second plumage, he correct, the curious case would he seen of a species regularly 
reverting from a higher stage of dress to a lower one and, subsequently, re-acquiring 
the more highly differentiated coloration. 
As pointing to the probability that both albescent, streaked individuals and also 
dark, spotted ones exist from the nest in the case of Spilornis^ Colonel Legge points 
out that of the Booted Eagle (Nisaetus pennatiis) both dark and light young ones 
have been taken out of the same nest; but the case is not strictly a parallel to that 
of Spilornis^ inasmuch as N. pennatus has two different phases of adult dress, a light 
and a dark one, and, when dimorphous pairs of young ones have been found, they 
are said to be sprung from a light male and dark female, or vice-versa (B. Ceylon, 62). 
The albescent plumage is found in both sexes. 
Skeleton. Length of cranium . 
Length of fibula 
84.0 
mni 
Greatest 
breadth of 
cranium 42.0 » 
» » tarso-metatarsus . 
. 76.0 
» 
Lenffth of humerus . 
97.0 » 
» » sternum 
61.0 
» ulna . . . 
110.0 » 
Greatest breadth of sternum 
. 35.5 
» 
» 
» radius . . 
HciP'bt nf r.rista, sterni . . 
13 5 
» 
» manus . . 
87.0 » 
Length of pelvis 
. 72 0 
» 
» femur . . 
65.0 ^ 
Greatest breadth of pelvis . 
. 31.5 
» 
» 
» tibia . . . 
(Siao, 
Sangi in Mus. Berol. XVII.) 
Nidification. Unknown. 
Distribution. Celebes. South Peninsula (W allace a 1, Guillemard a 14, Platen a 13, W eber 
a 17, etc.); Central Celebes — Luwu Distr. (Weber a 17, P. & E. Sarasin a 20); 
S.E. Peninsula — Kendari (Beccari a 7); E. Peninsula (Nat. Coll, a 21); N. Peninsula 
(Forster b 1, v. Duivenbode c 3, etc.); Talissi Id. (Hickson a 15); Lembeh Id. 
(Nat. Coll, in Dresd. Mus.); Siao — known only from skeleton (Meyer a XVI). 
2. Spilornis rufipectus sulaensis (Schl.). 
d. Circaetus sulaensis (I) Schh, Yalkv. Ned. Ind. 1866, 38, 72, pi. 23, figs. 4 — 6; (2) Gray, 
HL. 1869 I, 15. 
e. Spilornis sulaensis (1) Wall. Ibis 1868, 16; (2) Sharpe, Cat. B. 1874,1, 292; (3) Gurney, 
Ibis 1878, 102; (4) id. Diurn. B. of Prey 1884, 17; (5) Sharpe, Ibis 1893, 552. 
f. Circaetus rufipectus sulaensis (1) Schh, Mus. P.-B. Bev. Accip. 1873, 114. 
Figures and descriptions. Schlegel d I; Sharpe e 2. 
Diagnosis. Wing relatively shorter than in the typical 8. rufipectus (see table); under-side 
of quills greyish white, passing into blackish at the distal ends, and crossed by three 
or four well-marked bars of blackish, much narrower than those of the typical form. 
These bars do not coalesce on the basal half of the quills in the same manner as in 
that form, but pass separately across the wing. 
Distribution. Sula Islands, SulaBesi and SulaMangoli (Allen dl, Bernstein & Hoedt cJ, e7). 
In the Leyden Museum are seven specimens — 3 ad., 3 $ ad. and 1 $ juv. 
albescent — from Sula. The males have the breast paler; on the lower breast and 
