The brief appearance of the Ruddy Kingfisher (Halcyon coromanda), an uncommon passage migrant and winter visitor to Singapore, towards the end of October 2006 caused quite a stir among local birders (1, 2). The bright rufous plumage and red bill make identification easy. However, there is another distinguishing feature that most birders miss as it is only seen in flight (above). This is the “back and rump silvery white to azure-blue” patch, according to Wells (1999). In the juvenile bird the patch is “wholly blue rather than silvery.” The image above shows the bird perching on a branch and eying a prey on the ground. Note the bright dark brown iris. In the image above, taken just before the bird dived down to catch a prey, the eye is covered with a translucent layer, the nictitating membrane. This has a protective function as the bird plunges among the vegetation.
The close-up views of the eyes above show the normal eye (left) and covered with the nictitating membrane (right).
Input by Melinda Chan, images by Chan Yoke Meng.