138 NILS GYLDENSTOLPE, ZOOLOGICAL RESULTS OF THE SWEDISH ZOOLOGICAL EXPEDITIONS TO SIAM. 
DAVISON states that this species was »extremely common in every stream through- 
out the province» (Tenasserim) and Rosrnson & Kuoss found it »abundant everywhere 
on the coast and on the tidal estuaries, whereever there was mangroves» during their 
Expedition to the Northern parts of the Malay Peninsula. 
In Siam it must, however, be very rare and during my whole Expedition I only 
observed three specimens at the Meh Tha river in Northern Siam. One male in full plu- 
mage was shot here on the 4th of May 1914. 
Tt is neither included in WiILLIAMSON’s list of the birds of Bangkok, nor does BARTON 
mention it from Raheng and neighbourhood. 
292. Ardeola grayi. Sykes. — The Pond Heron. 
Ardeola grayi: Williamson 1 p. 48; Gairdner p. 31; Grant p. 116; Gairdner p. 152. 
do Koh Lak °/; 1915. L = 535 mm.; W = 227 mm.; T= 94 mm.; C = 68 mm.; Tarsus = 61 mm. 
— 2 Koh Lak 4/12 1914. L = 470 mm.; W = 198 mm.; T = 77 mm.; C = 57 mm.; Tarsus = 55 mm, — 
Irides: yellow. Bill: brownish black with the base of the lower mandible yellowish green. Legs: greenish yellow. 
The Pond Heron was very common in a mangrove swamp near Koh Lak in the 
Siamese Malaya. When I travelled down by rail from Bangkok to Koh Lak several 
specimens of a Pond Heron were observed on suitable localities along the railway line. 
These specimens probably all belonged to this species. 
In the North of Siam it is replaced by the Chinese Pond Heron to which it is very 
similar when in winter plumage. However, Ardeola grayi SYKES may be distinguished 
by its smaller size. 
The Pond Herons are most often seen on the paddy-fields where their plain colouring 
help them to escape notice, but when they take to flight their white wings make 
them a conspicuous object. Their note is very harsh and croaking. 
293. Ardeola bacchus. Br. — The Chinese Pond Heron. 
Ardeola bacchus: Gyldenstolpe I p. 78; Gyldenstolpe Il; Gyldenstolpe III p. 236; Robinson & Kloss p. 15; 
Robinson II p. 143; Robinson III p. 726. 
do Pak Koh #/1 1914. L = 498 mm.; W = 234 mm.; T = 95 mm.; C = 64 mm, — ¢ Pak Koh "/s 
1914. L = 495 mm; W = 204 mm.; T = 83 mm; C = 61 mm. — & Pak Koh %/; 1914. L = 460 mm.,; 
W = 204 mm.; T = 77 mm.; C = 61 mm. — Irides: vellow. Bill: horn colour (base of Jower mandible 
yellowish green). Jegs: yellowish green. 
The Chinese Pond Heron replaced the last-mentioned species in the Northern parts 
of the country, and it seems to live more along small creeks than on the paddy-fields or 
swamps. 
A fine male specimen in full breeding plumage was shot at Pak Koh on the 4th 
of April 1914. The other specimens obtained are in their winter plumage and then very 
similar to A. grayi SYKES, but even in that plumage the Chinese Pond Heron may be dis- 
tinguished by its slightly larger size. 
