Pulau Mantanani: 8 – 12 Oct 2012: Muscicapa Flycatchers

Asian Brown Flycatchers were among the commonest migrant passerines on Mantanani when I was there, with 19 sightings over the 4+ days.A selection of shots in various lighting conditions. Distinctive features of Asian Brown Flycatcher include the fairly chunky, broad-based bill which is basally yellow. The amount of brown wash across the breast is variable.I saw a couple of Brown-streaked Flycatchers, and managed to photograph one of them. These are described as an uncommon migrant to Borneo. Apart from the subtle diffuse brown streaks on the breast, another distinctive feature is the almost completely yellow lower mandible. On classic birds, only the tip is dark, though there is apparently some variability in this feature.

I saw three Dark-sided Flycatchers – all of them spotty juveniles.

Dark-sided can be rather easily confused with the rarer Grey-streaked Flycatcher, especially the juveniles, which can look long-winged, have rather obvious breast streaking, and can behave differently from adults, foraging close to the ground rather than in the mid or upper storey.However, Dark-sided can be identified in all plumages by the tiny bill and dark centres to some vent feathers. This latter feature is tricky to see in the field – being easier to judge on photos. Occasionally, even on photos, the vent can appear all white, so absence of this feature does not rule out Dark-sided.

Dark-sided typically has a rather domed head and looks small and ‘cute’. Juveniles have a ‘chess-board pattern’ of streaking on the breast, best seen when head-on.This is a Grey-streaked Flycatcher, taken in Miri, Sarawak, on 18 October by Anthony Wong. The different structure of this bird is apparent – it’s a larger, bigger-billed bird with a different head shape. There’s a great comparison of the structure of both species here. The bill of Grey-streaked is mostly dark (often looking all black). The breast streaks are distinct, long, pencil-like marks against a whitish background, quite different from either Dark-sided or Brown-streaked.

I don’t know, but suspect there may be a difference in moult timing between Grey-streaked and Dark-sided. There are photos of 1st winter Grey-streaked here on 29 Sep, and here on 1st Oct in Hong Kong where the moult into 1st non-breeding plumage is almost complete. Another first year bird photographed on 10th Oct in Taiwan here only has a few uppertail coverts still unmoulted. This suggests that Grey-streaked juveniles largely complete their post-juvenile moult before arriving in the wintering area. If so, a spotty Muscicapa in Borneo is likely to be a Dark-sided.

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