646 REPORT OF THE HARVARD AFRICAN EXPEDITION 
rains have abated somewhat and the drier season sets in. Apparently a similar 
disappearance is characteristic of the nighthawks for in the course of our 
stay which included the wettest months from July to November, no sign of 
the Long-tailed species (Scotornis climacurus) could be discovered though at 
other times it is known to be common, while the Pennant-winged and the 
Standard-winged species will probably be found to occur at suitable localities 
for they are well known at no very great distance from the borders of Liberia 
on the east and north. The two species of rollers we saw almost nothing of, 
though at proper seasons Biittikofer found them in hundreds hawking for insects. 
They probably make short migrations to other parts during the height of the 
rainy season. In all these cases it is quite likely that the torrential and often 
continuous rains tend to keep down the numbers of flying insects as well as 
to render the ground too wet for such species as habitually nest and rest upon 
it. These birds therefore remove to more favorable localities for part of the 
year, and in general, many of the native species do not commence nesting 
until the rains abate. 
Probably there is more or less irregularity in the movements of some of the 
colonial weaver birds that come and go according to the presence of abundant 
food or the need for proper nesting areas. Of their local migrations we learned 
very little, however. The blossoming and fruiting of various forest trees at 
different seasons no doubt has a certain effect in concentrating temporarily 
various species of sun-birds or of fruit-eating pigeons, hornbills, and others 
that are attracted by the abundance of their favorite food. The ripening of 
the fruit of the oil palms also brings many of the larger species to feed on the 
rich pulpy rind. 
The casual occurrence of many species is always to be expected, and we 
find a number of birds recorded which are evidently of infrequent appearance, 
among them the Flamingo, and Forbes’ Three-banded Plover (Afroxyechus 
forbes). 
On the other hand probably some species regularly visit Liberia at seasons 
of the year when conditions favor them. Of such is the Senegal Plover (Steph- 
anibyx lugubris) which according to Bittikofer regularly visits the more open 
places of the Cape Mount region in December and January. 
It will be interesting, as more data become available, to trace the changes 
in the avifauna from the forest region northward and eastward toward the 
areas of lesser rainfall until the more open and grass-grown portions of the 
interior are reached. Many species of birds seem to reach their limits of dis- 
tribution in southern Sierra Leone, approaching but seldom, if ever, crossing 
the Liberian border. Thus we saw at Freetown in that country numbers of 
vultures (Necrosyrtes monachus) but they are unknown in Liberia, nor are 
there any species of bustards or cranes, more typical of the open country. A 
comparison of our list with those of Kemp and Thompson for Sierra Leone 
reveals many other differences indicative of a change in the nature of the 
country and of the avifauna. 
