To tell these are Northern by:
1. Large, clean white rump and upper-tailed covert
2. Large, clean white vent and lower-tailed covert
3. White chin
4. Brown underwing
2015年12月22日 星期二
Northern House Martin 22 DEC 2015
Thanks to John Allcock again who found these Northern House Martin Delichon urbicum lagopodum, which is my 433th in HK.
To tell these are Northern by:
1. Large, clean white rump and upper-tailed covert
2. Large, clean white vent and lower-tailed covert
3. White chin
4. Brown underwing
To tell these are Northern by:
1. Large, clean white rump and upper-tailed covert
2. Large, clean white vent and lower-tailed covert
3. White chin
4. Brown underwing
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