Do brood parasitic Common Cuckoos develop brood patches during the breeding season?

Many birds develop brood patches on their ventral apterium under hormonal regulation to effectively transmit body heat to eggs during incubation.The developed patch has several characteristics,including de-feathering,vascularization,and edema.However,little is known about whether avian brood parasites that do not incubate their eggs exhibit brood patch development during the breeding season.In this study,we measured the size of the ventral apterium in 114 Common Cuckoos(Cuculus canorus)captured in the field throughout the breeding season and examined the appearance of the ventral apterium to confirm the development of brood patches.We also examined whether morphological traits and various factors correlated with the size of the ventral apterium(sternal apterium and abdominal apterium)and how it changed during the breeding season.We found no clear signs of brood patch development in Common Cuckoos captured throughout the breeding season,indicating that they likely did not develop brood patches on the ventral apterium during this period.We also found that ventral apterium size was positively correlated with wing length and body weight.In addition,Common Cuckoos with newly growing feathers on the boundary of the ventral apterium with pteryla were frequently observed as seasons progressed to the end.In conclusion,Common Cuckoos exhibit neither brood patch development nor the vestigial characteristics of ancestral brood patches,except for the growth of feathers on boundary the ventral apterium.Further studies examining brood patches across different groups of avian brood parasites are valuable for enhancing our understanding of the developmental and physiological adaptations of avian brood parasites.

A novel method to collect sperm from brood parasitic cuckoos:Urodeum stimulation(UroS)method

Sperm competition has been studied in numerous species as a representative example of postcopulatory sexual selection,where sampling sperm from male is the most basic and important step.Sperm collection can be tricky in birds,however,because unlike mammals,the genitals of birds are generally latent in the cloacal region and their characteristics vary among species.Various methods to collect sperm from different birds have been tested,such as cloacal massage,feces collection,and electro-stimulation,but their applicability varies depending on species.In this study,we introduced the urodeum stimulation method(UroS method)to collect sperm from Cuculus cuckoos,such as the Common Cuckoo(C.canorus).These species are expected to have interesting patterns of pair bonding and sperm competition because of their unique breeding strategy called brood parasitism;however,it remains unexplored.In this study,we described the application of our new method to expel semen from male common cuckoos,measured the volume of semen collected,checked the presence of sperm in the semen sample,and finally estimated its success rate among 82 males.Samples were successfully collected from 76 cuckoos(approximately 93%)and the colors and volumes of the samples were very diverse.Sperm was present in 43 of these samples(57%),showing a sperm observation rate approximately twice as high as that of the conventional cloacal massage method.We believe that this novel method will contribute to a better understanding of postcopulatory sexual selection in avian brood parasites and facilitate the process of sperm collection and artificial insemination in other medium-sized birds.

Comparing vocal structures of the parasitic and nonparasitic groups in Cuculinae

Background: Avian brood parasitism is a breeding strategy in which brood parasites lay their eggs in the nest of other species.This behavior is closely related to aspects of the biological evolution of the parasitic species such as reduced female body size and plumage color polymorphism.However,not much is known whether it is associated with the evolution of vocalization.Methods: We collected samples of the typical male calls of 67 species belonging to the sub?family Cuculinae.Using the calls,we measured five acoustic parameters for each samples to test the differences in vocal structures between parasitic and nonparasitic species.To control for potential phylogenetic effects,we also performed phylogenetic independent contrast analyses.Results: We found that vocal structures were relatively similar among the parasitic species with a tendency to simple and low?frequency calls.In addition,harmonic structures were observed more frequently in the nonparasitic group.Conclusions: Overall,these results support the idea that brood parasitic behavior with associated ecological condi?tions may play a role in vocal evolution,a better understanding of which may greatly improve our knowledge of vocal diversification in non?oscine birds.

Linking individual attributes and host specialization in brood parasitic cuckoos

Generalist avian brood parasites vary considerably in their degree of host specialization(e.g.,number of hosts);some parasitize the nests of just a few host species,whereas others exploit more than 100 species.Several factors,including habitat range,habitat type,and geographic location,have been suggested to account for these variations.However,inter-specific differences in individual attributes,such as personality and plasticity,have rarely been considered as potential factors of such variation,despite their potential relationship to,for example,range expansion.Using cage experiments,we tested the hypothesis that parasitic species exploiting more host species may be more active and exploratory.To this end,we quantified behaviors exhibited by two Cuculus cuckoos(Common Cuckoo C.canorus and Oriental Cuckoo C.optatus)that vary greatly in their number of host species.Specifically,we evaluated exploratory behavior displayed by birds in the cage,such as the number of movements,head-turning,wing-flapping,and stepping.The Common Cuckoo,which has a higher number of host species,tended to exhibit higher levels of exploratory behaviors than the Oriental Cuckoo.Our study showed that the two cuckoo species exhibited different exploratory levels,as predicted by the differences in their number of hosts.Further studies regarding the causality between individual attributes and host specialization with improved experimental methodology would greatly enhance our understanding of the role of individual characteristics in the coevolution of avian brood parasites and their hosts.

Egg color polymorphism and morph-ratio variation in Korean populations of the Vinous-throated Parrotbill

Understanding the occurrence of multiple distinct phenotypes in a population of a species,i.e.,polymorphism,is one of the challenges encountered in evolutionary biology.Egg color polymorphism in birds is one example of morphological polymorphism and disruptive selection has been proposed as a hypothetical mechanism to explain its occurrence.We studied how polymorphic egg colors(immaculate blue and white) occur in Korean populations of the Vinous-throated Parrotbill(Paradoxornis webbianus).Egg color ratios(the proportion of nests with blue eggs in a population) were monitored over a large spatial scale and egg colors were quanti ed using a spectrophotometer.We found egg color ratios to vary spatially among populations.Interestingly,there was a latitudinal morph-ratio cline in egg color ratios.e proportion of nests with blue eggs increased considerably with the latitude declined towards the southern part of the Korean peninsula.ere were some quantitative variations in egg colors among populations.However,the pattern of variations was not consistent with those of the population egg color ratios.Based on these results,we discuss a potential scenario for the evolution of egg color polymorphism in the Vinous-throated Parrotbill.