We assessed the age of birds based on the shape of their outer tail feathers.
Protobirds such as Confuciusornis had the same kind of feathers as modern birds; some specimens even display long tail feathers reminiscent of tropic birds and birds of paradise.
In an interesting adaptation for clinging to branches, the birds' stiff tail feathers act as additional support when they stand vertically on branches, two toes forward, two back.
We then averaged measurements from the right and left tail feather for both original and induced feathers.
It has been suggested that this decline in territorial aggression may be because large flight and tail feathers were growing at this time and would be easily damaged in a fight.
The male's body plumage is glossy black, and the wings and tail feathers are white.
We calculated asymmetry in tail length as the difference between the longest left tail feather and the longest right tail feather.
Most birds have two types of tail feather: flight feathers and tail-coverts.
Boldly dressed in black, brown, and white, males boast long, sharp tail feathers and dazzling display plumage.
Their white outer tail feathers are conspicuous in flight.
The white extends out the wings, but the primaries, secondaries, and tail feathers are mottled black-and-white.
Of the many sexually selected male traits now recognized, some of the classic examples most often cited are the elongated tail feathers of a number of bird species.
However, the outer tail feather is approximately 12 mm longer than the aerodynamic optimum for maneuvering flight.
With a three-foot wingspan and two long, streaming tail feathers, these birds are easy to recognize.
One of the most distinctive sounds of Wilson's Snipe is a winnowing sound made by air rushing through its stiff outer tail feathers as it dives from high in its display flight.
This feather was identified as a tail feather from the yellow-shafted race of this species, which generally ranges from central Alaska south to Montana.
If a similar male had both a green streak in the head and a curly tail feather, it was counted as a hybrid.
The tip of a tail feather was cut from each bird to avoid resampling in the same period.
Each gauge was firmly tied to the base of a single tail feather with a thread (dental floss).
We equipped the adults of study nests with one small magnet, attached to a tail feather with cloth-backed adhesive tape.