ML646264306

觀察細節

Although all of these swans showed a fairly wide black area (not pinched) where bill meets eye, and some seemed to show a straight slope from forehead down to bill tip, and we were initially convinced that we had some Trumpeter Swans here, there were some problems with that conclusion. Some of these swans had large bold yellow patches in their bills. Some did not, but all 5 swans were the same size. The line where white cheek met the black of bill was nearly vertical on all 4 adult swans, unlike the sloping line characteristic of Trumpeter. Bills just seemed short-looking. Trumpeter should have a longer-looking bill. For these reasons we have changed the identification of two of these swans from Trumpeter to Tundra.