ddavid

Yes, terns can be very confusing.  My thoughts are below - open to correction, of course.

1. 1st-Winter Common Tern. Dark edges to the front and rear of the inner wing with a pale rectangular area in the middle of the wing.

2. Left hand bird =  Aleutian Tern attaining winter plumage. White looking crown and a  conspicuous white  line in the  grey wing caused by white fringes to the median coverts. The right hand bird = juv Aleutian Tern (?).

3. Aleutian Tern. Conspicuous dark edge to the secondaries on the underwing. Also note on the right upperwing the conspicuous white line formed by white tips to the median coverts (as for Pic 2).

4. Juv Aleutian Tern (?) (same as in pics 2 & 10). Very dark upperparts.

5. Aleutian Tern. Head pattern.

6. Aleutian Terns left and right, Common Tern centre. Head pattern & jizz indicate Aleutian Terns. Common is smaller, not so long-winged and has a conspicuous dark (carpal) mark on the wing.

7.White-winged Black Tern. Face pattern with (almost) isolated dark smudge behind eye.

8. Common Tern. Dark carpal patch on wing.

9. White-winged Black Tern. Face pattern with isolated dark smudge behind eye. Also dark markings on covert tips on underwing.

10. Adult & juv (?) Aleutian Terns. The adult still retains an almost summer head pattern.

[ Last edited by ddavid at 29/09/2008 16:30 ]