Acrocephalus Orientalis Research Articles

Common cuckoo eggs are more resistant to puncture by the host

The puncture resistance hypothesis suggests that thick-shelled eggs of parasitic birds can resist puncture-ejection by the host. However, few experiments have yet been conducted to test this hypothesis in terms of natural host behavior (e.g., pecking at foreign eggs). To explore whether the eggshells of common cuckoos (Cuculus canorus) are resistant to puncture-ejection by their common hosts, Oriental reed warblers (Acrocephalus orientalis), we designed experiments to investigate if and how breeding Oriental reed warblers peck at foreign eggs that includes common cuckoo, Oriental reed warbler and budgerigar (Melopsittacus undulatus) eggs. The results showed that, given the same frequency of egg pecking, the probability of eggshell breakage was 87.5% for eggs of the Oriental reed warbler and 0% for eggs of the common cuckoo, with a significant difference (P = 0.001, Fisher's exact test). Our study shows clearly that common cuckoos' eggshells are less susceptible to puncture-ejection than those of Oriental reed warblers and budgerigars. This indicates that the eggshells of common cuckoos can resist host Oriental reed warblers' puncture-ejection, supporting the puncture resistance hypothesis.

Sparrowhawk imitation or convergent alarm signal? A new hypothesis for bubbling call of cuckoos with empirical testing

Abstract Alarm calls in bird vocalizations serve as acoustic signals announcing danger. Owing to the convergent evolution of alarm calls, some bird species can benefit from eavesdropping on certain parameters of alarm calls of other species. Vocal mimicry, displayed by many bird species, aids defense against predators and may help brood parasites during parasitism. In the coevolutionary dynamics between brood parasites, such as the common cuckoo (Cuculus canorus), and their hosts, female cuckoo vocalizations can induce hosts to leave the nest, increasing the probability of successful parasitism and reducing the risk of host attacks. Such cuckoo calls were thought to mimic those of the sparrowhawk. However, owing to their similarity to alarm calls, we propose a new hypothesis: female cuckoos cheat their hosts by mimicking the parameters of the host alarm call. In this study, we tested this new hypothesis and the sparrowhawk mimicry hypothesis simultaneously by manipulating the syllable rate in male and female common cuckoo vocalizations and playing them in front of the host Oriental reed warbler (Acrocephalus orientalis) for examination. The results indicate that similar to a normal female cuckoo call, a female call with a reduced syllable rate prompted the hosts to leave their nests more frequently and rapidly than male cuckoo calls. Additionally, the male cuckoo calls with increased syllable rate did not prompt the host to leave their nests more frequently or quickly compared with the male cuckoo calls with a normal syllable rate. Our results further confirm that female common cuckoos mimic the vocalizations of Eurasian sparrowhawks, reveal the function mechanisms underlying such mimicry, and support the theory of imperfect mimicry.

Breeding pairs with color aberrations in oriental reed warblers.

In 2017, one pair of Oriental reed warblers (Acrocephalus orientalis) with color aberrations was found in Yongnianwa National Wetland Park, Hebei, China. The female bird exhibited white feathers on the head, neck, and upper back, and the base of the beak was flesh-red in color. The male had a few feathers on the outer edges of the left and right primary wing coverts that were white, which was determined to be leucism after analysis. The breeding pairs laid their first egg on May 29, with a clutch size of four eggs. After an incubation period of 13 days, two chicks hatched on June 13, 2017. The nest was found empty on June 20 when the chicks were 7 days old and before fledging age; therefore, it was presumed that the chicks had been predated. A white parrot egg was added to the nest during the incubation period to test the egg recognition ability of breeding pairs and was successfully rejected. To the best of our knowledge, this is the first report of color aberrations in the Oriental reed warbler, and we found that this color aberrations did not affect some reproductive and antiparasitic behaviors of the birds, but whether it affects their breeding success needs to be further studied.

Three sympatric host nestlings eavesdrop on cuckoo nestling distress calls.

In predator-prey interactions, the prey faces extreme challenges from predation, which drives the evolution of defense or anti-predator mechanisms. Compared with adult birds, nestlings are more vulnerable but not helpless. However, data on whether nestlings eavesdrop on the danger signals transmitted by other prey nestlings and the mechanisms of eavesdropping remain limited. In brood parasitism, common cuckoo (Cuculus canorus) nestlings, raised by host adults who are not closely related, offer an instructive system for studying the transmission and recognition of danger signals among nestlings of different species that share special relationships. We played back the distress calls of common cuckoo nestlings to nestlings of three sympatric host species (the oriental reed warbler Acrocephalus orientalis, which is a primary host of the common cuckoo, the reed parrotbill Paradoxornis heudei, an occasional host, and the vinous-throated parrotbill Sinosuthora webbiana, which is not parasitized in the study area) to investigate whether the host nestlings reduced their begging behavior. We also quantified the degree of inhibition toward begging behavior for these nestlings. The results revealed that, in response to the distress calls, the three sympatric host species markedly suppressed their begging behavior. This response can likely be attributed to the innate response of host nestlings caused by the general characteristics of distress calls, rather than the acoustic similarity and phylogenetic relationship between host nestlings and cuckoo nestlings. Furthermore, we observed that upon hearing the distress calls of cuckoo nestlings, the oriental reed warbler nestlings exhibited the greatest reduction in the total number of calls compared to the other two host species, potentially owing to stronger predation and parasitic pressures. This study suggests that host nestlings can detect danger signals emitted by parasitic nestlings; however, further investigation is needed to determine whether they can respond to distress calls from unfamiliar nestlings in different regions.

Oriental reed warblers retain strong egg recognition abilities during the nestling stage.

Egg recognition and rejection are the most common and effective anti-parasitic strategies against avian brood parasitism in terms of maintaining stability over time and plasticity in response to environmental cues. Conversely, parasites have evolved multiple counter-adaptations to the anti-parasitic defenses of hosts. Among them, the crypsis hypothesis suggests that eggs that appear more cryptic in color and are closely matched to the environment are helping to counter the egg recognition strategy of the host. In this study, we investigated whether the egg recognition ability of Oriental reed warblers (Acrocephalus orientalis), a common host of common cuckoos (Cuculus canorus), changed during different reproductive stages by using model egg experiments. The effect of the crypsis hypothesis on the egg recognition ability of the hosts was also investigated by controlling the color contrast between the inside of the experimental nests and the model eggs. The results showed that the Oriental reed warbler retained strong egg recognition abilities, which were similar to the incubation stage (GLMMs: F 1,27 = 0.424, p = .521), even after entering the nestling stage and preferentially rejected model eggs with distinct contrasting colors (binomial test: Fisher's exact, p = .016). These results are consistent with the crypsis hypothesis. The present study suggests that the host retains a strong egg recognition ability even during the nestling stage and that cryptic-colored eggs that are closely matched with the breeding nest environment help counter the host's egg recognition abilities and increase the chances of successful parasitism by cuckoos. However, the effectiveness of cryptic egg may be weaker than mimic egg in countering egg recognition and rejection by hosts with open-cup nests.

Oriental Reed Warblers do not abandon Common Cuckoo chicks during prolonged nestling periods

The Oriental Reed Warbler (Acrocephalus orientalis) is one of the most commonly used hosts for the parasitic Common Cuckoo (Cuculus canorus). However, as hosts that feed unrelated parasitic nestlings may suffer extra reproductive costs, they may be less willing to care for nestlings that have prolonged nestling periods. To test this hypothesis, the duration of feeding by Oriental Reed Warblers under natural conditions for their own nestlings was compared with the duration of feeding under natural conditions for Common Cuckoo nestlings and for artificially prolonged cuckoo nestlings. The results showed that Oriental Reed Warblers did not starve, drive away, or desert any of the nestlings in the experiment, and neither parent was left alone. Our experimental study indicates that both Oriental Reed Warbler parents were willing to care for nestlings with a prolonged nestling period (up to 30 days, twice the average duration time that the Oriental Reed Warblers fed their own chicks in natural conditions). However, further experiments and observations are required in other host bird species to examine whether both parents or one of the parents may exhibit the behavior of abandoning nestlings with a prolonged nestling period.

Defense behavior of two closely related but geographically distant host species against cuckoo parasitism: A next test for the parallel coevolution.

Interactions between avian brood parasites, such as common cuckoos (Cuculus canorus), and their hosts are one of the best-studied examples of the coevolutionary arms race. Different stages of this arms race can be seen in different races of common cuckoos and their hosts across their range. However, little is known whether selected populations of two closely related but geographically distant species with probably different coevolutionary histories with the common cuckoo are also at different stages of the arms race. In this study, we tested this prediction experimentally using the same non-mimetic model eggs and three-dimensional (3D) printed models of the gray adult common cuckoo (Cuculus canorus). We examined egg recognition and egg rejection and aggression against the common cuckoo in the great reed warbler (Acrocephalus arundinaceus) and Oriental reed warbler (Acrocephalus orientalis), in Slovakia of Europe and northeast China of Asia. The results showed that the great reed warbler exhibited stronger responses to experimental model eggs and 3D models of the common cuckoo than the Oriental reed warbler. We conclude that both the great reed warbler and Oriental reed warbler have well-developed antiparasitic behaviors against common cuckoos in the studied populations, but with different levels of defense intensity, which may be due to local differences in parasitic pressure and the risk of parasitism. This provides an opportunity to study coevolutionary processes between the brood parasite and its hosts together in both species at large geographical scales.

Importance of cooperation: How host nest defenses effectively prevent brood parasitism from the cuckoos

As the frontline defense against avian brood parasitism, nest defense is important in reducing nest parasitism and increasing host fitness. However, systematic studies on its effectiveness (i.e., on whether it successfully prevents cuckoo parasitism) are scarce. Based on 214 video recordings from 10 years of field observations, we evaluated the effectiveness of nest defenses of the Oriental reed warbler (Acrocephalus orientalis) in deterring common cuckoo (Cuculus canorus) parasitism. Under a breeding pair situation (≤ 2 hosts individuals), warblers were hardly effective in resisting the egg-laying of the cuckoo and many of the cuckoos under attack were able to complete the parasitic process without being harmed. However, when hosts ≥ 3 individuals, the warblers could effectively thwart the cuckoos and cause lethal damage to the cuckoo in partial cases. This indicated that the host group effectively resisted the cuckoo, demonstrating the importance of cooperation among host neighbors in resisting cuckoo parasitism.

Fatal mobbing and attack of the common cuckoo by its warbler hosts.

Nest defense is an effective strategy of hosts against parasites. Typically, hosts will aggressively attack brood parasites that approach or visit their nests, which can prevent the parasites from laying eggs or may even lead to the death of the parasites. Few previous studies have specifically reported such fatal cases involving brood parasites and have attributed the cause of death to either drowning or hypothermia after falling into the water following an attack from hosts. In this study, we recorded the process of multiple host individuals of the Oriental reed warbler (Acrocephalus orientalis) mobbing and attacking a female common cuckoo (Cuculus canorus) in the field. We discovered that the immediate cause of the cuckoo's death was the fatal physical damage resulting from the aggressive defense from the hosts, suggesting that frantic pecking and scratching by the hosts is the most proximate cause of mortality among egg-laying female cuckoos. This finding enhances our essential understanding of the effectiveness of host attacks.

Anti-Predation Responses to Conspecific versus Heterospecific Alarm Calls by the Nestlings of Two Sympatric Birds.

Simple SummaryBirds can adjust their behavior by reacting to sound cues. Parents can adjust the feeding rate of nestlings by their response to begging calls. Acoustics play an important role in parent–offspring communication. When adults perceive predators, they can make mobbing alarm calls to warn other individuals. Chicks can also respond to the alarm calls of parents and thus reduce their predation risk. We tested whether the chicks of two species could hear, and respond to, conspecific and heterospecific acoustic alarm signals. Chicks were found to eavesdrop on conspecific and heterospecific mobbing alarm calls. Acoustical similarities between the alarm calls may explain why chicks can recognize heterospecific calls.Predation is generally the main cause of bird mortality. Birds can use acoustic signals to increase their predation survival. Bird response to mobbing alarm calls is a form of anti-predation behavior. We used a playback technique and acoustic analysis to study the function of mobbing alarm calls in the parent–offspring communication of two sympatric birds, the vinous throated parrotbill (Sinosuthora webbianus) and oriental reed warbler (Acrocephalus orientalis). The chicks of these two species responded to conspecific and heterospecific mobbing alarm calls by suppressing their begging behavior. The mobbing alarm calls in these two species were similar. Mobbing alarm calls play an important role in parent–offspring communication, and chicks can eavesdrop on heterospecific alarm calls to increase their own survival. Eavesdropping behavior and the similarity of alarm call acoustics suggest that the evolution of alarm calls is conservative and favors sympatric birds that have coevolved to use the same calls to reduce predation risk.

Female Cuckoo Calls Deceive Their Hosts by Evoking Nest-Leaving Behavior: Variation under Different Levels of Parasitism.

The common cuckoo (Cuculus canorus) is an obligate brood parasite that has evolved a series of strategies to trick its hosts. The female cuckoo has been hypothesized to mimic the appearance and sounds of several raptors to deceive the hosts into exhibiting anti-predator behavior. Such behavior would relax the protection of the host nest and thus allow the female cuckoo to approach the host nest unopposed. Many anti-parasite strategies have been found to vary among geographical populations due to different parasitic pressures from cuckoos. However, the effect of female cuckoo calls related to different levels of parasitic pressure has not been examined. Here, we studied the effect of female cuckoo calls on the oriental reed warbler (Acrocephalus orientalis), one of the major hosts of the common cuckoo, in two geographical populations experiencing different levels of parasite pressure. Four kinds of sounds were played back to the hosts: the calls from female common cuckoos, male common cuckoos, sparrowhawks (Accipiter nisus), and oriental turtle doves (Streptopelia orientalis). The results showed that the female cuckoo calls induced the hosts to leave their nests more frequently than the male cuckoo or dove calls in both populations, and two populations of the hosts reacted similarly to the female cuckoo calls, implying that the function of female cuckoo calls would not be affected by the difference in parasitism rate. This study indicates that female cuckoo calls function to distract the hosts' attention from protecting their nests. However, we propose that such a deception by the female cuckoo call may not be due to the mimicry of sparrowhawk calls, but rather that the rapid cadence of the call that causes a sense of anxiety in the hosts.

Common Cuckoo Nestling Adapts Its Begging Behavior to the Alarm Signaling System of a Host

Cuckoo nestlings thrive as avian brood parasites. To acquire sufficient food from the host parents, cuckoo nestlings generally make louder begging calls than host nestlings, but this may cause them to be more likely to attract the attention of predators. Studies have shown that nestlings would respond to the alarm calls of their parents by begging less, or crouching and remaining silent as an adaptation to reduce the risk of being heard by predators. Nevertheless, research is lacking on how parasite nestlings respond to alarm calls of their host parents. We studied the common cuckoo (Cuculus canorus) and one of the most common cuckoo host species, the oriental reed warbler (Acrocephalus orientalis), using a playback experiment in Yongnianwa National Wetland Park during the breeding seasons from June to July, 2020–2021. The begging behaviors of either cuckoo or host nestlings were quantified by playing back the alarm calls of host adults toward common cuckoo, sparrowhawk (Accipiter nisus), or oriental turtle doves (Streptopelia orientalis). Meanwhile, normal begging without playback, playback of the natural singing (NS) of host adults, and background noise (BN) were included as behavioral reference, non-threatening comparison, and playback control, respectively. The results showed that the cuckoo and host nestlings produced similar levels of begging with or without playback of NS and BN; however, both types of nestlings inhibited their begging intensity after hearing the playback of alarm calls, although they did not respond differently to the various alarm call playbacks. This study therefore elucidated that coevolution has selected the common cuckoo nestlings that adapt their begging behavior to the parent–offspring communication of alarm signaling in their host, oriental reed warblers.

Use of 3D-printed animal models as a standard method to test avian behavioral responses toward nest intruders in the studies of avian brood parasitism

Living and/or non-living animal models are often used as stimuli to observe the behavioral responses of the target animals. In the past, parasites, predators, and harmless controls have been used to test host anti-parasitism defense behavior, and their taxidermy specimens have been widely used as a set of standard methods for the study of avian brood parasitism. In recent years, with the rapid development of 3D-printing technology, 3D-printed bird models are expected to be applied as a standard method in the study of avian brood parasitism. To evaluate the use of 3D-printed models, this study tests the reaction of Oriental Reed Warbler (Acrocephalus orientalis) towards predators, parasites, or controls, and compares the reaction among different nest intruders and between taxidermy specimens and 3D-printed animal models. It was found that the Oriental Reed Warbler responded most aggressively to the parasite, followed by predator, and finally the control; the results were consistent between the reaction to taxidermy specimens and 3D-printed animal models, indicating that 3D-printed models could serve as a substitute for taxidermy specimens. We propose a series of advantages of using 3D-printed models and suggest them to be a standard method for widespread use in future studies of avian brood parasitism.

Experimental evidence that cuckoos preferentially parasitize host nests early in their laying cycle

Brood parasites, such as the Common Cuckoo (Cuculus canorus), rely on manipulating hosts from other species to raise their offspring. Selection should favor individuals that are able to identify and choose host nests that closely match the incubation stage of their own eggs. While intuitive, and supported by the findings of numerous long-term monitoring studies, experimental evidence of this remains sparse. By using video monitoring, we used three experimental groups to explore whether Common Cuckoos preferentially choose host Oriental Reed Warbler (Acrocephalus orientalis) nests that are early in their laying cycle. We found that Common Cuckoos preferentially parasitize nests of the host Oriental Reed Warbler that are earlier in their laying (less vs. more eggs) or nesting cycle (eggs vs. chicks), and videos of our experiments provide direct insights into their decision making process. Our results provide strong experimental evidence that Common Cuckoos are able to assess nesting stage and strategically choose nests that increase the likelihood of successful parasitism.

Parent-offspring and inter-offspring responses to conspecific versus heterospecific distress calls in 2 sympatric birds.

Distress calls, as a type of alarm call, play important roles in expressing bodily condition and conveying information concerning predation threats. In this study, we examined the communication via distress calls in parent-offspring and inter-offspring interactions. First, we used playback of chick distress calls of 2 sympatric breeders, the vinous-throated parrotbill Sinosuthora webbiana and the oriental reed warbler Acrocephalus orientalis, to the adults/chicks of these 2 species, respectively, and measured the responses of conspecifics or heterospecifics. The playback-to-chicks experiment showed that both species of chicks reduced the number of begging calls and begging duration time as a response to conspecific/heterospecific distress calls compared with natural begging and background noise controls. However, reed warbler chicks also reduced beak opening frequency in the response to conspecific distress calls compared with other playback stimuli. Second, the results of the playback-to-adults experiment showed that reed warbler adults could eavesdrop on distress calls of conspecific neighbors and sympatric heterospecifics. Furthermore, the nest-leaving behavior of reed warblers did not differ significantly when they heard the distress calls of conspecifics or parrotbills. Finally, reed warbler adults responded to heterospecific distress calls more quickly than to conspecific distress calls, and parrotbill adults presented the same response. Our results supported the warn-kin hypothesis and show that chick distress calls play an important role in conveying risk and the condition of chicks to enhance individual fitness. In addition, we also found that eavesdropping on distress calls is a congenital behavior that begins in the chick stage.

Egg mimicry and host selection by common cuckoos among four sympatric host species breeding within a reed habitat

AbstractIn the case of cuckoo parasitism, the maintenance of host specificity may be closely related to active host selection. In the reed wetlands of the Yongnian National Wetland Park, China, four host species of common cuckoos (Cuculus canorus) with similar nest structures breed sympatrically, namely, the Oriental reed warbler (Acrocephalus orientalis) (ORW), vinous-throated parrotbill (Sinosuthora webbiana) (VP), reed parrotbill (Paradoxornis heudei) (RP) and blunt-winged warbler (Acrocephalus concinens) (BW). Cuckoo parasitism rates on ORW (14.5%) and BW (18.2%) were found to be significantly higher than those on two species of parrotbills (RP 1.4% and VP 0%), and cuckoo eggs mimicked the size and coloration of ORW eggs significantly more closely than those of the eggs of the other three hosts. Egg recognition experiments revealed that the ability of ORW and VP to recognize nonmimetic eggs was significantly greater than that of BW and RP. Different life history strategies of the four hosts, including antiparasitic strategy, breeding time period and population density may partly explain the difference of parasitism in this multiple cuckoo-host system. Our study suggests that determining host life history traits and antiparasitic strategies are important for a better understanding of the specificity of host selection in common cuckoos.

Nest size matters: common cuckoos prefer to parasitize larger nests of Oriental reed warblers.

Avian brood parasites leave parental care of their offspring to foster parents. Theory predicts that parasites should select for large host nests when they have sufficient available host nests at a given time. We developed an empirical experimental design to test cognitive ability of female cuckoos in nest size by studying nest choice of common cuckoos (Cuculus canorus) among nests of its Oriental reed warbler (Acrocephalus orientalis) hosts. We presented three groups of experimental nests: 1) nest dyads tied together including one large and one small artificial nest from reed leaves, 2) nest triads tied together used the old modified warbler's own nests including enlarged, reduced and medium-sized nests, and 3) nest dyads are similar to group 1, but not tied together to elicit parasitism by common cuckoos. We predict that cuckoos prefer larger nest than medium one, the next is smaller nest. Our findings showed that common cuckoo females generally prefer large nests over medium or small sized nests in all three experimental groups. Furthermore, cuckoo parasitism was significantly more common than in previous studies of the same warbler population, implying that larger, higher and more exposed host nests effectively increased the probability of cuckoo parasitism.

Egg rejection and egg recognition mechanisms in Oriental Reed Warblers

BackgroundNest parasitism by cuckoos (Cuculus spp.) results in enormous reproductive failure and forces hosts to evolve antiparasitic strategies, i.e., recognition of own eggs and rejection of cuckoo eggs. There are often sexual conflicts between male and female individuals in the expression of antiparasitic behavior due to the differences in reproductive inputs and division of labor.MethodsBy adding a foreign egg made of blue soft clay to the host nest during early incubation period in the field, and by removing several host eggs and adding experimental eggs to control the proportion of two egg types in the nest, we examined egg rejection ability, egg recognition mechanism and sexual difference in egg rejection of the Oriental Reed Warbler (Acrocephalus orientalis), one of the major hosts of Common Cuckoos (Cuculus canorus).ResultsOur results indicated that Oriental Reed Warblers can recognize and reject nearly 100% (73/75) of the non-mimetic eggs made of blue soft clay, and they could reject foreign eggs with 100% accuracy, regardless of the ratio of experimental eggs and its own eggs in the nest. Furthermore, all cases of egg rejections recorded by videos were only carried out by females.ConclusionsOriental Reed Warblers have a high egg recognition ability and show a true recognition mechanism. Only female warblers perform egg rejection, suggesting that the sex for host egg incubation seems to play an important role in the evolution of egg recognition mechanisms.

Testing the Interspecific Function of Female Common Cuckoo “Bubbling” Call

Female common cuckoo (Cuculus canorous) predator-like “bubbling” calls distract host parental attention and reduce the egg rejection rate. Such “bubbling” calls are also frequently used to attract males and deter territorial rivals in intraspecies contact, and these calls are an ancestral character in many cuckoo species. Although hosts have had sufficient time to become familiar with this call and evolve anti-parasitic strategies, why are the hosts fooled by this “bubbling” call? We propose two hypotheses. The first hypothesis proposes that call variation reduces the opportunity for host species to correctly assess cuckoo tricks. In contrast, the second hypothesis proposes that the cost of behavior may prevent the antiparasitic strategy from evolving. In the study, we tested the prerequisites of these hypotheses, by investigating whether cuckoo calls vary during the day and testing whether the predator-like calls suppress bird activities. Based on field recordings from three different areas, we found high overlap in the calls generated during different periods. Oriental great reed warblers (Acrocephalus orientalis), a host species, did not show different responses toward the playback of female common cuckoo calls generated before noon or afternoon. Based on bird count data, we found that predator-like call playback is insufficient for suppressing bird activities. Therefore, none of the prerequisites were supported by our field data. We discuss the potential reasons for our findings and hope to inspire more research examining female cuckoo vocalizations.

Behavioral and Acoustic Responses of the Oriental Reed Warbler (Acrocephalus orientalis), at Egg and Nestling Stages, to the Common Cuckoo (Cuculus canorus)

Cuckoo nest parasites lay eggs in host nests and thereby transfer all reproduction costs to the hosts. This greatly reduces host fitness. Parasitism has selected for the evolution of anti-parasitic strategies in hosts, including nest defense. The dynamic risk assessment hypothesis holds that nest parasitism only threatens the nests during the egg stage, so hosts should reduce the level of defense against nest parasites after the egg stage. We studied the behavioral and acoustic responses of oriental reed warblers (Acrocephalus orientalis), during both the egg and nestling stages, toward the common cuckoo (Cuculus canorus), sparrowhawks (Accipiter nisus) and oriental turtle doves (Streptopelia orientalis). A. orientalis can visually distinguish cuckoos from sparrowhawks and doves, indicating that hawk mimicry did not work for the cuckoos. The behavioral response of hosts in the nestling stage was stronger than in the egg stage, which supports the offspring value hypothesis and suggests that cuckoos may also act as nest predators. However, there was no difference in the alarm calls A. orientalis produce in response to different invaders, indicating that different types of alarm calls may not contain specific information.