Editing Cuckoo (section)

===== Parasitic cuckoo advanced laying and hatching =====
The cuckoo egg hatches earlier than the host eggs, and the cuckoo chick grows faster. In most cases, the chick evicts the eggs and/or young of the host species. The chick has no time to learn this behavior, nor does any parent stay around to teach it, so it must be an [[instinct]] passed on genetically.

[[File:Reed warbler cuckoo.jpg|thumb|upright|A [[reed warbler]] raising the young of a [[common cuckoo]]]]
One reason for the cuckoo egg's hatching sooner is that, after the egg is fully formed, the female cuckoo holds it in her oviduct for another 24 hours prior to laying.<ref name=Davies_book /> This means that the egg has already had 24 hours of internal incubation. The cuckoo's internal temperature is 3–4&nbsp;°C higher than the temperature at which the egg is incubated in the nest, and the higher temperature means that the egg incubates faster, so at the time it is laid, the egg has already had the equivalent of 30 hours incubation in a nest.<ref name=Davies_book />

The chick encourages the host to keep pace with its high growth rate with its rapid begging call<ref name=Adams>{{cite news |url= https://www.telegraph.co.uk/earth/wildlife/4109282/Cuckoo-chicks-dupe-foster-parents-from-the-moment-they-hatch.html |archive-url= https://web.archive.org/web/20090213190416/http://www.telegraph.co.uk/earth/wildlife/4109282/Cuckoo-chicks-dupe-foster-parents-from-the-moment-they-hatch.html |url-status= dead |archive-date= February 13, 2009 | work=The Daily Telegraph | location= London | title=Cuckoo chicks dupe foster parents from the moment they hatch | quote=Cuckoo chicks start to mimic the cries that their foster parents' young make from the moment they hatch, a scientist has proved. | first=Stephen | last=Adams | date= 2009-01-04 | access-date=2010-04-30}}</ref> and the chick's open mouth which serves as a [[sign stimulus]].<ref name=Campbell>''Biology'' (4th edition) NA Campbell, p. 117 'Fixed Action Patterns' (Benjamin Cummings NY, 1996) {{ISBN|0-8053-1957-3}}</ref>