Editing Tree swallow (section)

==Status==
The tree swallow is considered to be [[least concern]] by the [[International Union for Conservation of Nature]]. This is due to the bird's large range of about {{convert|834000|km2|mi2|abbr=on}},<ref name="iucn status 12 November 2021" /> and its stable population, estimated to be about 20,000,000 individuals.<ref name="hbw"/> It is protected in the US by the [[Migratory Bird Treaty Act of 1918]],<ref>{{cite web | url = https://www.fws.gov/birds/management/managed-species/migratory-bird-treaty-act-protected-species.php | year=2013|title = Migratory Bird Treaty Act Protected Species (10.13 List) | publisher = US Fish & Wildlife Service | access-date = 4 June 2018}}</ref> and in Canada by the [[Migratory Birds Convention Act]].<ref>{{cite web|url=https://www.canada.ca/en/environment-climate-change/services/migratory-birds-legal-protection/convention-act.html|title=Birds protected under the Migratory Birds Convention Act|date=2017|access-date=21 July 2018|publisher=Government of Canada|archive-url=https://web.archive.org/web/20190520104408/https://www.canada.ca/en/environment-climate-change/services/migratory-birds-legal-protection/convention-act.html|archive-date=20 May 2019|url-status=dead}}</ref> In some parts of the US, the range of this swallow has extended south, likely due to changes in land use, the reintroduction of beavers, and nest boxes installed for [[bluebird]]s. The tree swallow is negatively impacted by the clearing of forests and the reduction of marshes, the latter reducing the habitat available for wintering. This swallow has to compete for nest sites with the [[common starling]], [[house sparrow]] (both introduced to [[North America]]),<ref name="hbw"/> bluebirds,<ref name="Wiebe2016">{{cite journal|last1=Wiebe|first1=Karen L.|title=Interspecific competition for nests: Prior ownership trumps resource holding potential for mountain bluebird competing with tree swallow|journal=The Auk|volume=133|issue=3|year=2016|pages=512–519|issn=0004-8038|doi=10.1642/AUK-16-25.1|doi-access=free}}</ref> and the [[Northern house wren|house wren]] (which also destroys nests without occupying them).<ref name="Finch1990">{{cite journal|last1=Finch|first1=Deborah M.|title=Effects of predation and competitor interference on nesting success of house wrens and tree swallows|journal=The Condor|volume=92|issue=3|year=1990|pages=674–687|issn=0010-5422|doi=10.2307/1368686|jstor=1368686}}</ref> Acidification of lakes can force this swallow to go relatively long distances to find calcium-rich items, and can result in chicks eating plastic.<ref name="St. LouisBreebaart1991"/> Other chemicals, like pesticides and other pollutants, can become highly concentrated in eggs, and [[Polychlorinated biphenyl|PCB]]s are associated with the abandonment of a pair's clutch.<ref name="hbw"/> Contamination from oil sands mine sites can negatively affect tree swallows by increasing the presence of toxins, as measured by the activity of ethoxyresorufin-''o''-deethylase (a detoxification enzyme) in nestlings. This normally has little influence on nestling and fledging,<ref name="SmitsWayland2000">{{cite journal|last1=Smits|first1=Judit E.|last2=Wayland|first2=Mark E.|last3=Miller|first3=Michael J.|last4=Liber|first4=Karsten|last5=Trudeau|first5=Suzanne|title=Reproductive, immune, and physiological end points in tree swallows on reclaimed oil sands mine sites|journal=Environmental Toxicology and Chemistry|volume=19|issue=12|year=2000|pages=2951–2960|issn=0730-7268|doi=10.1002/etc.5620191216|bibcode=2000EnvTC..19.2951S |s2cid=85573498 }}</ref> though extreme weather can reveal the effects: a 2006 study found that nestlings from wetlands most polluted by [[oil sands]] processing material were more than 10 times more likely to die than those from a control site during periods of synchronized cold temperatures and heavy rainfall, compared to the lack of difference in mortality between the groups when the weather was less extreme.<ref name="GentesWaldner2006">{{cite journal|last1=Gentes|first1=Marie-Line|last2=Waldner|first2=Cheryl|last3=Papp|first3=Zsuzsanna|last4=Smits|first4=Judit E.G.|title=Effects of oil sands tailings compounds and harsh weather on mortality rates, growth and detoxification efforts in nestling tree swallows (''Tachycineta bicolor'')|journal=Environmental Pollution|volume=142|issue=1|year=2006|pages=24–33|issn=0269-7491|doi=10.1016/j.envpol.2005.09.013|pmid=16297515|bibcode=2006EPoll.142...24G }}</ref> A 2019 paper, however, found that increased precipitation caused a similar decline in hatching and nestling success for nestlings both near and far from oil sands sites.<ref name="GodwinBarclay2019">{{cite journal|last1=Godwin|first1=Christine M.|last2=Barclay|first2=Robert M. R.|last3=Smits|first3=Judit E. G.|title=Tree swallow (''Tachycineta bicolor'') nest success and nestling growth near oil sands mining operations in northeastern Alberta, Canada|journal=Canadian Journal of Zoology|volume=97|issue=6|year=2019|pages=547–557|issn=0008-4301|doi=10.1139/cjz-2018-0247|doi-access=free|bibcode=2019CaJZ...97..547G }}</ref> In another study, birds exposed to mercury fledged, on average, one less chick than those not, an effect amplified by warm weather.<ref name="HallingerCristol2011">{{cite journal|last1=Hallinger|first1=Kelly K.|last2=Cristol|first2=Daniel A.|title=The role of weather in mediating the effect of mercury exposure on reproductive success in tree swallows|journal=Ecotoxicology|volume=20|issue=6|year=2011|pages=1368–1377|issn=0963-9292|doi=10.1007/s10646-011-0694-1|pmid=21553259|bibcode=2011Ecotx..20.1368H |s2cid=42492417}}</ref> In addition, cold weather events can rapidly reduce the availability of aerial insect prey,<ref>{{Cite journal|last1=Winkler|first1=David W.|last2=Luo|first2=Miles K.|last3=Rakhimberdiev|first3=Eldar|date=September 2013|title=Temperature effects on food supply and chick mortality in tree swallows (Tachycineta bicolor)|url= |journal=Oecologia|language=en|volume=173|issue=1|pages=129–138|doi=10.1007/s00442-013-2605-z|issn=0029-8549|pmc=3751296|pmid=23468236|bibcode=2013Oecol.173..129W}}</ref> and in some populations with advancing reproduction may result in reduced offspring survival.<ref>{{Cite journal|last1=Shipley|first1=J. Ryan|last2=Twining|first2=Cornelia W.|last3=Taff|first3=Conor C.|last4=Vitousek|first4=Maren N.|last5=Flack|first5=Andrea|last6=Winkler|first6=David W.|date=2020-09-28|title=Birds advancing lay dates with warming springs face greater risk of chick mortality|journal=Proceedings of the National Academy of Sciences|volume=117|issue=41|language=en|pages=25590–25594|doi=10.1073/pnas.2009864117|pmid=32989166|pmc=7568286|bibcode=2020PNAS..11725590S |s2cid=222159036|issn=0027-8424|doi-access=free}}</ref>