Editing Tree swallow (section)

==Description==
[[File:Juvenile Tree Swallow (Tachycineta bicolor).jpg|thumb|A juvenile tree swallow]]

The tree swallow has a length between about {{convert|12|and|14|cm|in|abbr=on}} and a weight of approximately {{convert|17|to|25.5|g|oz|abbr=on}}. Wingspan ranges from {{convert|30|to|35|cm|in|abbr=on}}.<ref>{{Cite web|title=Tree Swallow Identification, All About Birds, Cornell Lab of Ornithology|url=https://www.allaboutbirds.org/guide/Tree_Swallow/id|access-date=2020-09-28|website=www.allaboutbirds.org|language=en}}</ref> The male has mostly glossy blue-green {{birdgloss|upperparts}}, the wings and tail being blackish. The {{birdgloss|underparts}}<ref name="hbw"/> and the cheek patch are white,<ref name="Turner"/> although the {{birdgloss|underwing}} coverts are gray-brown.<ref name="hbw"/> The bill is black, the eyes dark brown, and the legs and feet pale brown.<ref name="Turner"/> The female is duller in color than the male, and sometimes has a brown forehead.<ref name="hbw"/> The second-year{{refn|group=note|Second-year refers to the second year of life; therefore, a "second-year female" is one year old.<ref name="Hussell1983"/>}} female also has brown upperparts, with a variable number of blue feathers; some third-year females also retain a portion of this subadult plumage.<ref name="Hussell1983">{{cite journal|year=1983|last=Hussell|first=David J. T.|title=Age and plumage color in female tree swallows|journal=Journal of Field Ornithology|volume=54|issue=3|pages=312–318}}</ref> According to a 1987 study, this likely allows a younger female to explore nest sites, as the resident male is usually less aggressive to a subadult female.<ref name="StutchburyRobertson1987">{{Cite journal| doi = 10.1093/auk/104.4.717 | issn = 0004-8038| volume = 104| issue = 4| pages = 717–723| last1 = Stutchbury| first1 = Bridget J.| last2 = Robertson| first2 = Raleigh J.| title = Signaling subordinate and female status: Two hypotheses for the adaptive significance of subadult plumage in female tree swallows | journal = The Auk | url = https://sora.unm.edu/sites/default/files/journals/auk/v104n04/p0717-p0723.pdf | date = October 1987 }}</ref> A 2013 study found that the resident female was less aggressive towards second-year female models when they were presented separately from older models. Why the female eventually replaces its subadult plumage is unknown; it may allow males to assess female quality, as pairs [[assortative mating|mate assortatively]] based on plumage brightness.<ref name="CoadyDawson2013">{{cite journal|last1=Coady|first1=Chelsea D.|last2=Dawson|first2=Russell D.|title=Subadult plumage color of female tree swallows (''Tachycineta bicolor'') reduces conspecific aggression during the breeding season|journal=The Wilson Journal of Ornithology|volume=125|issue=2|year=2013|pages=348–357|issn=1559-4491|doi=10.1676/12-155.1|s2cid=85030082}}</ref> The juvenile tree swallow can be distinguished by its brown upperparts and gray-brown-washed breast.<ref name="hbw"/>

===Voice===
[[File:Tree Swallows - Minneapolis Minnesota - Birds Calling.jpg|left|thumb|Two tree swallows singing]]
{{Birdsong|url=https://www.xeno-canto.org/species/Tachycineta-bicolor|species=tree swallow|song1=Tachycineta bicolor - Tree Swallow XC134156.ogg|caption song1=Song of the tree swallow}}
The tree swallow's song consists of three parts: the chirp, the whine, and the gurgle. These sections may be repeated or omitted, and all can stand alone. The first, as the chirp call (sometimes divided into the contact call and solicitation call), is made by the female during copulation<ref name="SharmanRobertson1994">{{cite journal|last1=Sharman|first1=M. Y.|last2=Robertson|first2=R. J.|last3=Ratcliffe|first3=L. M.|title=Vocalizations of the tree swallow (''Tachycineta bicolor'') during the pre-laying period: A structural and contextual analysis|journal=American Midland Naturalist|volume=132|issue=2|year=1994|pages=264–274|issn=0003-0031|doi=10.2307/2426582|jstor=2426582}}</ref> and in both sexes to stimulate the nestlings to beg<ref name="LeonardFernandez1997"/> or (in some populations) when their mate leaves or enters the nest cavity. The whine, generally consisting of a downward shift in frequency followed by an upward shift, may be given alone as the anxiety call,<ref name="SharmanRobertson1994"/> occasionally made in response to certain predators.<ref name="Winkler1992">{{cite journal|last1=Winkler|first1=David W.|title=Causes and consequences of variation in parental defense behavior by tree swallows|journal=The Condor|volume=94|issue=2|year=1992|pages=502–520|issn=0010-5422|doi=10.2307/1369222|jstor=1369222|s2cid=45389696}}</ref> The gurgle, as when it appears at the end of the song, is usually uttered twice. It is likely involved in pair bonding. The chatter call is used to advertise nest sites (the reason it is also known as the "nest-site advertising call") and is also given to intruding conspecifics. A short high-pitched submission call is sometimes uttered after an aggressive encounter with another tree swallow. While being physically restrained or in pain, a distress call may be given. The male often utters a ticking (or rasping) aggression call during copulation, and both sexes use it at the end of mobbing dives. The alarm call is given in reaction to predators and other intruders,<ref name="SharmanRobertson1994"/> and can serve to induce older nestlings to crouch and stop begging when a predator is near.<ref name="McIntyreHorn2014">{{cite journal|last1=McIntyre|first1=Emma|last2=Horn|first2=Andrew G.|last3=Leonard|first3=Marty L.|title=Do nestling tree swallows (''Tachycineta bicolor'') respond to parental alarm calls?|journal=The Auk|volume=131|issue=3|year=2014|pages=314–320|issn=0004-8038|doi=10.1642/AUK-13-235.1|s2cid=86754716|doi-access=free}}</ref>

Communication between parents and offspring can be disrupted by human-generated noise. A 2014 study, for example, found that broods for whom white noise was played were less likely to crouch or stop begging in response to alarm calls. Parents did not alter their calls to compensate, likely increasing predation risk.<ref name="McIntyreLeonard2014">{{cite journal|last1=McIntyre|first1=Emma|last2=Leonard|first2=Marty L.|last3=Horn|first3=Andrew G.|title=Ambient noise and parental communication of predation risk in tree swallows, ''Tachycineta bicolor''|journal=Animal Behaviour|volume=87|year=2014|pages=85–89|issn=0003-3472|doi=10.1016/j.anbehav.2013.10.013|s2cid=53173370}}</ref> Noise can also disrupt whether parents respond to begging, but this may be balanced out by the louder calls nestlings give when exposed to it. Increased begging effort, however, may be ineffective or costly for louder levels of noise.<ref name="LeonardHorn2015">{{cite journal|last1=Leonard|first1=Marty L.|last2=Horn|first2=Andrew G.|last3=Oswald|first3=Krista N.|last4=McIntyre|first4=Emma|title=Effect of ambient noise on parent–offspring interactions in tree swallows|journal=Animal Behaviour|volume=109|year=2015|pages=1–7|issn=0003-3472|doi=10.1016/j.anbehav.2015.07.036|s2cid=53160897}}</ref><!-- Maybe add this to a paragraph about industry's effects on the tree swallow in the "status" section -->