. Bulletin of the British Ornithologists' Club. [Bull. 1977: 97(3)] 86 Figure 1. Average wing-tips of williamsoni and four subspecies of Muscicapa latirostris, drawn to scale. Numbers in parentheses are sample sizes and the vertical bars represent the range of short-fall behind the wing tip of primaries 1, 4, 5, 6, 9 and 10 (descendant).. williamsoni (12) latirostris (11) siamensis (3) segregata (6) randi(&) M. I. segregata of Sumba island, Lesser Sundas, or M. I. randi which Amadon 6 DuPont (1970) have guessed is resident in the Philippines; and finally what is known of the timing
. Bulletin of the British Ornithologists' Club. [Bull. 1977: 97(3)] 86 Figure 1. Average wing-tips of williamsoni and four subspecies of Muscicapa latirostris, drawn to scale. Numbers in parentheses are sample sizes and the vertical bars represent the range of short-fall behind the wing tip of primaries 1, 4, 5, 6, 9 and 10 (descendant).. williamsoni (12) latirostris (11) siamensis (3) segregata (6) randi(&) M. I. segregata of Sumba island, Lesser Sundas, or M. I. randi which Amadon 6 DuPont (1970) have guessed is resident in the Philippines; and finally what is known of the timing of moult. Among almost all resident insectivores, at least in Malaysia, moult occurs June-October, yet only two of 16 william- soni examined show moult, including the type (an adult male) dated 3 August, from south Thailand, in which primaries 1-6 (descending) are new, 7 is growing, 8-10 are old and rectrices 2-6 are growing, while a post- juvenile male, dated 30 July, from south Burma, is growing some tail- and wing-coverts and body feathers. Most of the others have wings and tail unworn and the total freshness of the August male from Fraser's Hill sug- gests that, like northern latirostris (Stresemann & Stresemann 1974, Nisbet & Neufeldt 1975), adults normally complete all moult before they migrate, although juveniles retain their remiges and rectrices until later. The excep- tional two could have suffered arrest of moult during migration, as sometimes occurs in autumn among Lanius cristatus and Locustella certhiola wintering in Malaysia (Medway & Wells 1976.) The above arguments, of course, merely weaken certain previous as- sumptions, and although williamsoni^ siamensis and latirostris form a pur- suasive chromatic cline, the only positively fresh clue to relationships is a possible williamsoni - latirostris intergrade (SM 458) dated 16 November 1956 from Ulu Simunjan, south Sarawak (Borneo). This is an adult female, wing- length 72 mm, tail 50 mm, tarsus 14 mm,
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