Editing Parasitism (section)

==== Brood parasitism ====

{{further|Brood parasitism}}

In [[brood parasitism]], the hosts suffer increased parental investment and energy expenditure to feed parasitic young, which are commonly larger than host young. The growth rate of host nestlings is slowed, reducing the host's fitness. Brood parasites include birds in different families such as [[cowbird]]s, [[Viduidae|whydahs]], [[cuckoo]]s, and [[black-headed duck]]s. These do not build nests of their own, but leave their eggs in nests of other [[species]]. In the family ''[[Cuckoo|Cuculidae]]'', over 40% of cuckoo species are obligate brood parasites, while others are either facultative brood parasites or provide parental care.<ref>{{Cite book |last=Payne |first=R. B. |title=The Cuckoos |date=September 15, 2005 |publisher=Oxford University Press |year=2005 |isbn=9780198502135 |edition=1st |location=Oxford |language=en}}</ref> The eggs of some brood parasites [[mimicry|mimic]] those of their hosts, while some cowbird eggs have tough shells, making them hard for the hosts to kill by piercing, both mechanisms implying selection by the hosts against parasitic eggs.<ref name=Payne1997>{{cite book |last=Payne |first=R. B. |date=1997 |chapter=Avian brood parasitism |editor1=Clayton, D. H. |editor2=Moore, J. |title=Host–parasite evolution: General principles and avian models |pages=[https://archive.org/details/hostparasiteevol1997unse/page/338 338–369] |publisher=Oxford University Press |isbn=978-0-19-854892-8 |chapter-url=https://archive.org/details/hostparasiteevol1997unse/page/338 }}</ref><ref>{{cite journal |last1=Rothstein |first1=S. I. |year=1990 |title=A model system for coevolution: avian brood parasitism |journal=Annual Review of Ecology and Systematics |volume=21 |pages=481–508 |doi=10.1146/annurev.ecolsys.21.1.481}}</ref><ref name="DeMarsico2013">{{cite journal |last1=De Marsico |first1=M. C. |last2=Gloag |first2=R. |last3=Ursino |first3=C. A. |last4=Reboreda |first4=J. C. |title=A novel method of rejection of brood parasitic eggs reduces parasitism intensity in a cowbird host |journal=Biology Letters |volume=9 |issue=3 |date=March 2013 |doi=10.1098/rsbl.2013.0076 |pmid=23485877 |pages=20130076|pmc=3645041 }}</ref> The adult female [[European cuckoo]] further mimics a predator, the [[European sparrowhawk]], giving her time to lay her eggs in the host's nest unobserved.<ref name=Welbergen2011>{{cite journal |last1=Welbergen |first1=J. |last2=Davies |first2=N. B. |year=2011 |title=A parasite in wolf's clothing: hawk mimicry reduces mobbing of cuckoos by hosts |journal=[[Behavioral Ecology (journal)|Behavioral Ecology]] |volume=22 |issue=3 |pages=574–579 |doi=10.1093/beheco/arr008|doi-access=free }}</ref> Host species often combat parasitic egg mimicry through egg [[Polymorphism (biology)|polymorphism]], having two or more egg phenotypes within a single population of a species. Multiple phenotypes in host eggs decrease the probability of a parasitic species accurately "matching" their eggs to host eggs.<ref>{{Cite journal |last=Yang, C., X. Si, W. Liang, and A. P. Møller |title=Spatial variation in egg polymorphism among cuckoo hosts across 4 continents |url=https://doi.org/10.1093/cz/zoaa011 |journal=Current Zoology |date=2020 |volume=66 |issue=5 |pages=477–483 |doi=10.1093/cz/zoaa011 |pmid=33293928 |pmc=7705517 |via=Oxford Academic}}</ref>