Editing Bird migration (section)

==Adaptations==

Birds need to alter their metabolism to meet the demands of migration. The storage of energy through the accumulation of fat and the control of sleep in nocturnal migrants require special physiological adaptations. In addition, the feathers of a bird suffer from wear-and-tear and must be moulted. The timing of this moult – usually once a year but sometimes twice – varies with some species moulting prior to moving to their winter grounds and others molting prior to returning to their breeding grounds.<ref>{{cite book |editor1-first=Greenberg |editor1-last=R. |editor2=Marra, P. P. |page=94 |title=Birds of two worlds: the ecology and evolution of migration |publisher=Johns Hopkins University Press |year=2005 |isbn=978-0-8018-8107-7 |chapter=Ecology and Demography of East-West Differences in Molt Scheduling of Neotropical Migrant Passerines |last=Rohwer |first=S. |author2=Butler, L. K. |author3=DR Froehlich  |name-list-style=amp}}</ref><ref>{{cite journal |title=Adaptations to migration in birds: behavioural strategies, morphology and scaling effects |journal=Philosophical Transactions of the Royal Society B |year=2008 |volume=363 |pages=287–299 |doi=10.1098/rstb.2007.2140 |pmid=17638691 |last=Hedenström |first=A. |issue=1490 |pmc=2606751}}</ref> Apart from physiological adaptations, migration sometimes requires behavioural changes such as flying in flocks to reduce the energy used in migration or the risk of predation.<ref>{{cite journal |author=Weber, Jean-Michel |title=The physiology of long-distance migration: extending the limits of endurance metabolism |journal=Journal of Experimental Biology |year=2009 |volume=212 |pages=593–597 |doi=10.1242/jeb.015024 |pmid=19218508 |issue=Pt 5 |s2cid=12520138 |url=http://jeb.biologists.org/content/jexbio/212/5/593.full.pdf|doi-access=free |bibcode=2009JExpB.212..593W }}</ref>