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16,4 McGregor: Some Features of the Philippine Ornis 399 
known to eat monkeys."* In contrast to this ponderous eagle 
is the butterfly falcon, Microhierax erythrogenys (Vigors), 
which is no larger than a large sparrow. 
LOCAL ABUNDANCE OF CERTAIN SPECIES OF BIRDS 
A curious condition is found in some small islands, where one 
or more local species may be common over the entire area of 
the island, even if there be but little forest. Thus, Dicruropsis 
cuyensis (McGregor) is found all over Cuyo, and Zosterops rich- 
mondi McGregor fairly swarms on Cagayancillo; but neither 
genus is represented on the other island. Hypsipetes fugensis 
Grant and Leptocoma henkei (Meyer) are extremely abundant 
on both Fuga and Calayan. The latter species is found in 
Luzon also, but is not nearly so abundant as it is in the small 
northern islands. Hyloterpe fallax McGregor is one of the most 
abundant species on Calayan. Terpsiphone periopthalmica 
(Grant) is confined to Batan and is fairly abundant in forest 
over most of that island; the type specimen of this species came 
from Malabon, near Manila, but it must have been a straggler. 
DISCONTINUOUS DISTRIBUTION OF SPECIES 
This superabundance of one or a few species on a small island 
where other species occur in no more than their normal numbers 
seems to indicate that there are unusually favorable conditions 
on these small islands for some species. Another curious con- 
dition is the absence of a species from an island on which it 
is reasonable to expect it to occur. Thus, Corvus philippinus 
Bonaparte, a large, conspicuous bird, which is abundant in most 
islands, does not occur on Camiguin Island, north of Luzon, 
although it is found in Calayan, Fuga, and Luzon. Pyecnonotus 
goiavier (Scopoli), one of the commonest and most universally 
distributed among Philippine species does not occur on any of 
the islands north of Luzon. Somewhat allied to this condition 
is the discontinuous, or interrupted, distribution of a species. 
Centropus carpenteri Mearns, of Batan Island, is very slightly 
if at all different from C. mindorensis (Steere), of Mindoro; 
yet no species like either of these is found on any of the in- 
termediate islands or on any other island. Camiguinia helene 
(Steere) is abundant on Camiguin, north of Luzon, but is 
unknown south of there until northern Mindanao is reached. 
Specimens from these two localities are indistinguishable. Chlo- 
ropsis flavipennis (Tweeddale) is one of the characteristic birds 
of Cebu and appears also in northern Mindanao. The first 
* See Clemens, J., Condor 9 (1907) 92. 
