The other interesting raptor I saw was much closer (see photos below). It looked to me like a Black Kite on structure (note the long tail and angular wings) but seemed to have some plumage anomalies (relatively uniform dark brown underparts, reduced whitish patches on the inner primaries (not extending to outher primaries). The tail was splayed as the bird was circling, and the tail appears to be heavily worn, so no fork is evident. This bird had me confused for a while - after initially thinking Black Kite I started to wonder if it was actually an Aquila eagle, but the tail is clearly too long and the bird too "dainty", the carpel bars on the upperparts (see the poor quality pic below) are also consistent with Black Kite, however, in the same picture note the white "landing lights" on the shoulders and the narrow white rump. This bird is actually a dark phase BOOTED EAGLE, a species I have very little experience of, and only ever in light phase. Interesting bird...ok, let's be honest..."confusing bird", but a good lesson learned! I have to thank Sacha Barbato for inadvertently alerting me to the possibility of this bird being a booted eagle - I had forgotten that Booted occurs in Thailand, Robson (2008) considers it to be a vagrant or rare passage migrant in much of Thailand, though Robert Candido reports it as regular at raptor watchpoints on the Thai-Malay peninsular (eg Chumphon). Thanks also to Phil Round who has confirmed the ID.
Dark phase Booted Eagle
Further along on my journey back I stopped briefly at Bung Boropet, which was heaving with birdlife including BRONZE-WINGED JACANA, PURPLE SWAMPHEN, and STRIATED GRASSBIRD, LONG-TAILED SHRIKE, ORIENTAL PRATINCOLE, and a few YELLOW BITTERNS.
female Yellow Bittern
Whilst driving further south it was evident that migrating hirundines (especially RED-RUMPED SWALLOWS) and BLACK DRONGOS were being forced down by the frequent heavy rain showers. The icing on the cake at sunset was a Harrier spp (probably Pied) quartering a field about 30kms north of Bangkok, but I was charging down the dual carriageway, looking into the sun so couldn't clinch it.