Editing Feather (section)

=== Feathers used in mating displays ===
In sexually dimorphic birds, males often develop distinct coloration or specialized ornamental feathers used in mating displays to attract mates. There are several proposed theories for the origin of ornamental feathers, with the first observed instances being observed in multiple early [[Theropoda|theropods]]<ref name=":1">{{Cite journal |last1=Xu |first1=Xing |last2=Barrett |first2=Paul M. |date=2025-02-19 |title=The origin and early evolution of feathers: implications, uncertainties and future prospects |journal=Biology Letters |volume=21 |issue=2 |pages=20240517 |doi=10.1098/rsbl.2024.0517 |pmc=11837858 |pmid=39969251}}</ref><ref>{{Cite journal |last1=Campione |first1=Nicolás E. |last2=Barrett |first2=Paul M. |last3=Evans |first3=David C. |date=12 March 2020 |title=On the Ancestry of Feathers in Mesozoic Dinosaurs |url=https://link.springer.com/chapter/10.1007/978-3-030-27223-4_12 |journal=The Evolution of Feathers from Their Origin to the Present |series=Fascinating Life Sciences |pages=213–243 |doi=10.1007/978-3-030-27223-4_12 |isbn=978-3-030-27222-7 |via=Springer|url-access=subscription }}</ref> (see subsection on Origins below). 

The most well-known example of ornamental feathers used in mating is male [[Peafowl|peacocks]] (''Pavo cristatus)''. Males sport a long train of covert feathers with distinct eyespot patterns, which are coupled with a vigorous display in the courtship process. When performing these displays, males flash their train in a fanning motion, showing their plumage off to females. 

The evolutionary origin of the peacock’s ornamental feathers and display remains unclear, with multiple theories proposing a combination of factors. In a study observing peacock display behavior, captive male peacocks had the length of their trains, the length of their torsi, and the density of the eyespots measured. They were then released into enclosures with female peacocks, with their mating success measured in successful copulations. The results showed that [[female choice]] was not influenced by train size, but by eyespot density. This suggests that male peacocks’ elaborate feathers and displays evolved as a result of female choice, particularly favoring males with more eyespot patterns<ref>{{Cite journal |last1=Loyau |first1=Adeline |last2=Jalme |first2=Michel Saint |last3=Sorci |first3=Gabriele |date=2005 |title=Intra- and Intersexual Selection for Multiple Traits in the Peacock (Pavo cristatus) |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1439-0310.2005.01091.x |journal=Ethology |language=en |volume=111 |issue=9 |pages=810–820 |doi=10.1111/j.1439-0310.2005.01091.x |bibcode=2005Ethol.111..810L |issn=1439-0310|url-access=subscription }}</ref>. 

==== Structure and use ====
The bone morphology of the radius, ulna, and humerus which support ornamental feathers can also affect female choice<ref name=":2">{{Cite journal |last1=Friscia |first1=Anthony |last2=Sanin |first2=Gloria D. |last3=Lindsay |first3=Willow R. |last4=Day |first4=Lainy B. |last5=Schlinger |first5=Barney A. |last6=Tan |first6=Josh |last7=Fuxjager |first7=Matthew J. |date=2016 |title=Adaptive evolution of a derived radius morphology in manakins (Aves, Pipridae) to support acrobatic display behavior |url=https://onlinelibrary.wiley.com/doi/10.1002/jmor.20534 |journal=Journal of Morphology |language=en |volume=277 |issue=6 |pages=766–775 |doi=10.1002/jmor.20534 |pmid=27027525 |issn=1097-4687|url-access=subscription }}</ref>. For example, the bone morphology of male [[Club-winged manakin|club-winged manakins]] (''Machaeropterus deliciosus'') is highly specialized, with larger and denser ulnas that are bigger in volume and have higher mineral density compared to others in the manakin family<ref name=":2" /><ref>{{Cite journal |last1=Bostwick |first1=Kimberly S. |last2=Riccio |first2=Mark L. |last3=Humphries |first3=Julian M. |date=2012-06-13 |title=Massive, solidified bone in the wing of a volant courting bird |journal=Biology Letters |volume=8 |issue=5 |pages=760–763 |doi=10.1098/rsbl.2012.0382 |pmc=3440988 |pmid=22696286}}</ref>. The secondary feathers are enlarged and are used in mating displays; males knock the tips of the enlarged feathers together repeatedly in a “jump and snap” motion, producing a distinctive sound. The display ends with a “beard up” motion, in which the male shows off their long yellow throat feathers rapidly while performing jumps.

==== Tail Length ====
Tail length is another example of feathers playing a role in mate choice, as seen in the [[long-tailed widowbird]] (''Euplectes progne''). The males of this species have extremely long tail feathers during the mating season, which correlates with higher success in attracting mates<ref name=":3">{{Cite journal |last=Andersson |first=Malte |date=October 1982 |title=Female choice selects for extreme tail length in a widowbird |url=https://www.nature.com/articles/299818a0 |journal=Nature |language=en |volume=299 |issue=5886 |pages=818–820 |doi=10.1038/299818a0 |bibcode=1982Natur.299..818A |issn=1476-4687|url-access=subscription }}</ref>. In a famous study testing the correlation between tail length and [[Fitness (biology)|fitness]], male widowbirds had their tail lengths artificially shortened or elongated and those with elongated tails had higher mating success. It was alternatively proposed that longer ornamental feathers played a role in territory defense and intrasexual competition, as a way of displaying dominance, but there was  no substantial evidence supporting this theory<ref name=":3" />.

==== Origin of ornamental feathers ====
One possible origin of ornamental feathers is in the megalosauroid ''[[Sciurumimus]]'', which have a simple, monofilamentous morphology. Monofilamentous feathers have a single, thread-like structure, as opposed to branches or barbs, and are considered to be the earliest form of feather<ref name=":1" />. Monofilamentous feathers have also been found in a wide range of taxa, though ''Sciurumimus'' was the earliest. Monofilamentous feathers have also been found in the tyrannosauroid ''[[Yutyrannus]]'' and the therizinosauroid ''[[Beipiaosaurus]]'', with proportionally broader monofilaments that were likely a form of early specialized ornamental feathers<ref name=":1" />. 

An analysis of feathers discovered in Burmese [[amber]] revealed unusual coloration along the [[rachis]], suggesting they bore striking color patterns. Early ornamental feathers in the genus ''[[Schizooura]]'' suggest an aerodynamic use as well as an ornamental one, with the pin-tailed shape being too narrow to impact aerodynamics<ref name=":1" />.