Editing Tree swallow (section)

===Predation===
The tree swallow is susceptible to a wide range of predators. Eggs, nestlings, and adults in the nest fall victim to [[Pantherophis obsoletus|black rat snakes]], [[American crow]]s, [[American kestrel]]s, [[common grackle]]s, [[northern flicker]]s, [[chipmunk]]s, [[Peromyscus|deermice]], [[domestic cat]]s, [[weasel]]s,<ref name= Winkler>Winkler, D. W.; Hallinger, K. K.; Ardia, D. R.; Robertson, R. J.; Stutchbury, B. J.; Chohen, R. R. (2011). Poole, A. F., ed. "Tree Swallow (''Tachycineta bicolor'')". ''The Birds of North America''. [[Ithaca, New York]]: Cornell Lab of Ornithology.</ref> [[American black bear]]s,<ref name="ZachMayoh1984">{{cite journal|last1=Zach|first1=Reto|last2=Mayoh|first2=Keith R.|title=Gamma radiation effects on nestling tree swallows|journal=Ecology|volume=65|issue=5|year=1984|pages=1641–1647|issn=0012-9658|doi=10.2307/1939142|jstor=1939142|bibcode=1984Ecol...65.1641Z }}</ref> and [[raccoon]]s.<ref>Chapman, L. B. (1955). "Studies of a tree swallow colony". ''Bird-Banding''. '''6''' (2): 45–70.</ref> While flying or perched, predators to the tree swallow include American kestrels, [[black-billed magpie]]s,<ref name= Winkler/> [[barred owl]]s,<ref>Errington, P. L. (1932). "Food habits of southern Wisconsin raptors. Part I. Owls". ''The Condor''. '''34''' (4): 176–186.</ref> [[great horned owl]]s, [[Merlin (bird)|merlins]], [[peregrine falcon]]s, and [[sharp-shinned hawk]]s. While evasive flight is the usual response to predators in free-flying swallows, mobbing behavior is common around the nest,<ref name= Winkler/> and is directed not just towards predators, but also towards nest site competitors, who might be scared off by it.<ref name="Winkler1992"/> This behavior involves the swallow swarming and diving towards (but not actually striking) the intruder<ref name= Winkler/> from around {{convert|5|to|20|m|ft|abbr=on}} above the ground, usually giving soft ticking calls near the end and coming within about {{convert|0.5|to|2|m|ft|abbr=on}} of the predator.<ref name="Winkler1992"/> It seems to alter the intensity of its attacks based on which predator approaches;<ref name= Winkler/> a 1992 study found that ferrets elicited a more vigorous defense than black rat snakes,<ref name="Winkler1992"/> and a 2019 thesis similarly discovered that black rat snake models were dived at the least and [[eastern chipmunk]] models the most.<ref name="Maass2019">{{cite thesis|last=Maass|first=Natalia May|title=Perceived predation risk and the responses of adult and nestling tree swallows (''Tachycineta bicolor'')|year=2019|type=[[Master of Science|MS]]|publisher=[[Eastern Kentucky University]]}}</ref> It is suggested that the snake prompted a weaker response because defense behaviors may be less effective<ref name="Winkler1992"/> and more dangerous to perform against it.<ref name="Maass2019"/>