Montane, 14.4 per cent were Submontane and 84 per cent were Lowland species. The distribution of birds 12 miles north of Kalabakan closely resembled that at Quoin Hill except for the total absence of Montane species and an increase of Submontane species to 25 per cent. The observation of fewer species (48) can be attributed to the nearly uniform habitat.

The avifauna in the moss forest 5.5 miles southwest of Tenom was unusual in that 45.4 per cent consisted of Lowland species; this locality lies 4,000 feet above sea level, yet only 27.3 per cent of its species were Submontane and 27.3 per cent Montane. If one looks at these figures from the standpoint of the actual importance of the three groups at this place, however, a different picture emerges. Some of the Lowland species were seen only once while I was there and few were common, while all of the Submontane and most of the Montane forms were more or less common.

SEASONALITY OF BREEDING

The breeding season in North Borneo.—Birds in the Quoin Hill area of eastern Borneo seem to breed most commonly in June, July, and August. Table 2 lists 34 of the more common species at Quoin Hill for which evidence on breeding was available. The actual evidence was provided by females with active brood patches or active ovaries, males with enlarged testes, birds in juvenal plumage, or birds actively in annual molt. From such data dates of presumed breeding were extrapolated. In Table 2, the solid black lines indicate dates for which both male and female were in breeding condition. The dotted lines indicate enlarged testes but no evidence of breeding in females. In the bottom line of Table 2, the figures indicate the percentage of the population breeding in any one month. For instance, 2.9 per cent of the birds were breeding in March, but 73 per cent were breeding in June. Rainfall records from the Cocoa Research Station from April, 1959, to December, 1964, were available to me. These data, along with the average for each month, are given in Table 3. There appears to be little correlation between rainfall and breeding season at Quoin Hill. A true dry season in the Quoin Hill area does not occur, but monthly rainfall has varied from 0.57 inches to 21.27 inches in a single year.

TABLE 2.—Seasonality of common breeding birds at Quoin Hill. Solid lines indicate times of occurrence of known breeding; dotted lines represent times of presumed breeding.