Editing Bird migration (section)

===Vagrancy===
{{See also |Vagrancy (biology)#In birds}}

Migrating birds can lose their way and appear outside their normal ranges. This can be due to flying past their destinations as in the "spring overshoot"{{anchor |overshoot}} in which birds returning to their breeding areas overshoot and end up further north than intended. Certain areas, because of their location, have become famous as watchpoints for such birds. Examples are the [[Point Pelee National Park]] in Canada, and [[Spurn]] in [[England]].

[[Reverse migration (bird migration)|Reverse migration]], where the genetic programming of young birds fails to work properly, can lead to rarities turning up as vagrants thousands of kilometres out of range.<ref>{{cite journal |url=http://www.zmuc.dk/VerWeb/staff/kthorup/Kt-pdf/BirdStudy51-228.pdf |title=Reverse migration as a cause of vagrancy |author=Thorup, Kasper |journal=Bird Study |year=2004 |volume=51 |issue=3 |pages=228–238 |doi=10.1080/00063650409461358 |bibcode=2004BirdS..51..228T |s2cid=51681037 |access-date=2014-06-15 |archive-url=https://web.archive.org/web/20170525094621/http://www.zmuc.dk/VerWeb/staff/kthorup/Kt-pdf/BirdStudy51-228.pdf |archive-date=2017-05-25 |url-status=dead}}</ref>

[[Drift migration]] of birds blown off course by the wind can result in "falls" of large numbers of migrants at coastal sites.<ref name="migrating" />

A related phenomenon called "abmigration" involves birds from one region joining similar birds from a different breeding region in the common winter grounds and then migrating back along with the new population. This is especially common in some waterfowl, which shift from one flyway to another.<ref>{{cite journal |last1=Guillemain |first1=M. |last2=Sadoul |first2=N. |last3=Simon |first3=G. |year=2005 |title=European flyway permeability and abmigration in Teal Anas crecca, an analysis based on ringing recoveries |journal=Ibis |volume=147 |issue=4 |pages=688–696 |doi=10.1111/j.1474-919X.2005.00446.x}}</ref>