Egg-Laying Behavior Of Common Cuckoo(Cuculus Canorus):Proposal And Verification Of The Delivery Hypothesis

Avian brood parasitism lays eggs in the nests of other individuals(host)and allows the host to hatch and care for offspring.This special reproductive process is a classic model system for studying coevolution.Among them,the laying egg process of nest parasites is the core segment to study their coevolution with the host.When laying eggs,parasites usually take 1-2 host eggs.This phenomenon has attracted much attention.For more than half a century(1965-2016),researchers have put forward eight hypotheses to explain this behavior,and some have been well verified.But ultimately,there is no unified solution and convincing.In order to explore the significance of common cuckoo(Cuculus canorus)egg removing,this paper first used 455 Oriental reed warbler(Acrocephalus orientalis)nests observed in Zhalong National Nature Reserve of Heilongjiang Province for 7 years to study and analyze,of which 250 nests were parasitic by common cuckoo,and 53 clear common cuckoo parasitic videos were recorded at random.Through the detailed analysis of the video,this paper records a series of actions related to the spawning process of cuckoo.By analyzing and summarizing the parasitic process of common cuckoo,it is found that common cuckoo does not care whether the host is present or not.They will boldly resist the attack and lay eggs,and bite the host's eggs when laying eggs,which may or may not take away the host's eggs.Aiming at the egg picking behavior of common cuckoo,this paper puts forward a new hypothesis-delivery hypothesis,that is,egg picking helps to produce eggs more quickly,so as to avoid attracting the attention of the host or reducing the fatal attack of the host.Delivery hypothesis attempts to explain common cuckooe removing behavior,which is a novel point of view.In order to verify this view,we further designed relevant verification experiments.The experimental study was conducted in Zhalong National Nature Reserve of Heilongjiang Province and Sifangtuozi farm of Baicheng City,Jilin Province in 2021(May to August).The main parasitic systems in the two places are common cuckoo Oriental reed warbler,and common cuckoo has a high parasitic rate on the Oriental reed warbler of the two samples.The existence of delivery hypothesis can be effectively proved by capturing the egg lay time of common cuckoo parasitic Oriental reed warbler in different situations.Three groups of experiments were set up,which were empty nest(0 eggs),ovary(1-5 eggs)and blue stick model egg to attract cuckoo parasitism.The spawning speed of their nests with 0 eggs,1-5eggs and blue model column were compared,and whether the egg picking or pecking had an effect on the egg laying speed was analyzed.By comparing the spawning time,it is found that the time taken for cuckoo to bite and lay eggs is significantly reduced compared with that when there are no eggs in the nest.This study believes that biting the eggs in the nest and blue stick model egg can significantly accelerate the spawning of common cuckoo.In all parasitic cases,common cuckoos will pick up objects in their nests.Even if they are empty nests,they will try to find eggs and finally egg laying.This study well verifies the existence of delivery hypothesis.Common cuckoo tends to look for eggs or other objects in the nest to bite during spawning.The main purpose of egg biting is to produce eggs more quickly,so as to avoid encounter with the host,and taking away the host egg is only a side-effect of egg biting.