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.

============================================================================
SPECIES | J | F | M | A | M | J | J | A | S | O | N | D
----------------------------+---+---+---+---+---+---+---+---+---+---+---+---
_Treron curvirostra_ | | | | | | | ....-----| | |
_Cacomantis merulinus_ | | | | | | | | --------..........
_Chalcites malayanus_ | | | | | | -------- | | | |
_Phaenicophaeus | | | | | | | | | | | |
curvirostris_ | | | | | ------------ | | | |
_Collocalia fuciphaga_ | | | | | | ..------ | | | |
_Chaetura leucopygialis_ | | | | | ------| | | | | |
_Harpactes diardi_ | | | | | ------------.... | | |
_Eurystomus orientalis_ | | | | --------- | | | | | |
_Calorhamphus fuliginosus_ | | | | | | -------.......| | |
_Megalaima chrysopogon_ | | |