Egg Recognition Ability Research Articles

Recognition of nestmate eggs in the ant Formica fusca is based on queen derived cues

Abstract Inclusive fitness benefits depend on recognizing the right individuals to interact with. Social insect nests protect themselves from non-kin intruders through nestmate recognition based on chemical cues. The recognition cues on adult individuals are from a mixture of genetic and environmental sources, but the ontogeny and use of recognition cues on eggs has not been previously assessed. We studied recognition by workers of eggs that were either nestmates or non-nestmates. and the ontogeny of recognition cues on eggs in the ant Formica fusca, a species with precise egg recognition abilities. Workers were able to discriminate among freshly laid eggs with no nest derived cues on them, and the egg surface chemicals varied among nests in these eggs, suggesting that queen derived cues are used in nestmate recognition. The results are discussed in the light of their implications on deceptive social parasite strategies and within colony conflicts.

Increase of clutch size triggers clutch destruction behaviour in common moorhens (Gallinula chloropus) during the incubation period

Conspecific brood parasitism (CBP) is common in a variety of animal taxa, including birds. In coots (Fulica spp.), and the closely related moorhens (Gallinula spp.), such parasitism is especially common, and hosts experience considerable costs through increased chick competition soon after hatching. Hence, these birds have evolved egg recognition and rejection abilities, e.g., egg counting, burying the foreign eggs, assigning them suboptimal positions within the mixed clutch, or deserting parasitized clutches. For common moorhens (Gallinula chloropus) it has been shown that desertion of parasitized nests pays most at the early egg laying stage. Later on, the costs of desertion exceed the costs of brood parasitism and acceptance is favoured. Here we tested moorhen egg discrimination behaviour during the incubation stage when acceptance of foreign eggs is expected. Four treatments were applied: (1) single added non-mimetic pale blue egg, (2) single added non-mimetic white chicken egg, (3) four foreign conspecific eggs added to the clutch and (4) four foreign conspecific eggs exchanged for four host eggs. Moorhens responded by egg destruction (47%) only to the increased clutch size but not to foreign egg colour and size match. In three nests where egg destruction occurred, all the eggs in the mixed clutch were destroyed by pecking, in two other nests one of the foreign eggs were pecked, while two other nests were deserted. These results are puzzling since moorhens have been shown to possess refined egg recognition abilities. To our knowledge, such destruction of parasitized clutches by moorhens during incubation has not previously been reported. We suggest that after clutch completion, moorhens use increase in clutch size as a cue to determine if they have been parasitized, and some individuals choose to reject parasitic eggs by deserting or destroying the whole clutch.

The importance of nest‐site and habitat in egg recognition ability of potential hosts of theCommonCuckooCuculus canorus

The intensity of selection exerted by brood parasites on their hosts depends on the proportion of nests that are parasitized and the fitness costs of parasitism. Nest detection by brood parasites influences the probability of parasitism, and we propose that the difficulty faced by brood parasites of finding nests on the ground may make ground‐nesting species subject to lower levels of parasitism, causing a reduction in levels of defence compared with species breeding in shrubs, trees and elsewhere above the ground. We tested the prediction that the rejection rate ofCommonCuckooCuculus canoruseggs by hosts is inversely related to the frequency with which they build nests on the ground, both at local and at continental scales. First, we used estimates of the rejection rate of non‐mimetic model eggs experimentally introduced into the nests of 26 potential host species breeding in theSierraNevadaMountains of southernSpain. Most species tested in theSierraNevada showed high rejection rates of both mimetic and non‐mimetic eggs, whereas theEuropeanRobinErithacus rubecula, with a low rejection rate, was the only species that was regularly parasitized. At the continental scale we used all available published information on rejection rates of non‐mimetic models by European hosts of theCommonCuckoo. The frequency of ground‐nesting explained interspecific variation in rejection rate of non‐mimetic model eggs both for the species tested in theSierraNevada and for allEuropean hosts after controlling for all other life‐history variables known to affect rejection rates. An effect of the abundance of trees in a particular habitat, previously shown to affect parasitism by theCommonCuckoo, was only apparent from analyses of continental‐scale data and not from theSierraNevada mountains, suggesting that particular properties of mountainous areas affectCommonCuckoo parasitism. Ground‐nesting species showed lower rejection rates than species breeding in bushes or trees. These results suggest that species nesting on the ground may have suffered lower parasitism pressures in their historical coevolutionary interactions with theCommonCuckoo.

House sparrows selectively eject parasitic conspecific eggs and incur very low rejection costs

Most host species of obligate interspecific brood parasites are under strong selection because such parasitism, e.g., that involving evictor nestmates, is highly costly. Egg rejection is one of the most efficient host defences against avian brood parasites. Many hosts have thus evolved egg-recognition ability and rejection behaviour. However, this defensive mechanism has not evolved in most species where only intraspecific brood parasitism occurs, probably because (1) the eggs of conspecific females are very similar in appearance, making egg rejection less likely to emerge, and (2) such parasitism is frequently less costly than interspecific parasitism. Using a captive population of house sparrows (Passer domesticus) with a low breeding density, we here provide new evidence showing that this species actually has a fine capacity to discriminate conspecific eggs and to eject them (44.2% of foreign eggs ejected) while incurring very low rejection costs (4.2% of own eggs ejected). This result contradicts those previously found in high-density house sparrow populations in which very high rejection costs and very high clutch desertion rates were reported, probably as a consequence of intraspecific competition and infanticide provoked by the high breeding density. The house sparrow has only rarely been reported as the host of an interspecific brood parasite, which implies that it is a newly described example of an altricial species in which egg ejection has evolved and is maintained in response to intraspecific brood parasitism.

Strategy selection under conspecific brood parasitism: an integrative modeling approach

Conspecific brood parasitism (CBP), where females lay eggs in nests of conspecifics, is taxonomically widespread. Following recent calls to consider CBP in a more integrative manner, we explore breeding strategies related to CBP by using a model of competing strategies that incorporates variation in individual quality, relatedness, recognition of own versus parasite-laid eggs, as well as the costs of egg laying and postlaying care. Our model creates 5 main conclusions. First, variation in individual quality plays a central role in shaping breeding strategies. Second, kinship plays a central role in the evolution of CBP. Third, egg recognition ability may affect the prevalence of parasitism: If hosts recognize parasitic eggs, relatedness between host and parasite facilitates CBP. Fourth, the relative costs of egg laying and postlaying care play a so far underestimated role in determining the prevalence of parasitism. Fifth, natal philopatry may lead to a reduction in productivity. To sum up, our theoretical study combines factors known to affect both breeding in general and CBP in particular and shows that these factors can explain a large proportion of the variation in CBP strategies found in the wild and therefore facilitates the understanding of the mechanisms shaping these strategies. Key words: breeding strategy, conspecific brood parasitism, cost of breeding, egg recognition, individual quality, kinship. [Behav Ecol]

Absence of egg discrimination in a suitable cuckooCuculus canorushost breeding away from trees

There is at present considerable variation in the level of antiparasite defences among different host species of avian brood parasites, but in many potential hosts some individuals reject poorly matching parasite eggs. Here we present unique absence of egg discrimination behaviour backed up by a lack of egg recognition abilities in a suitable common cuckooCuculus canorushost, the skylarkAlauda arvensis. Skylarks did not show any clear rejection response to experimentally added highly non‐mimetic foreign eggs in any behavioural context, even before they had started laying or when the whole clutch was exchanged with foreign eggs. This absence of antiparasite defence can be explained by the breeding habitat of larks consisting of largely treeless open landscapes where cuckoos have little access to the nests, thereby eroding the possibility of coevolutionary interactions. Our results are strikingly consistent with the spatial habitat structure hypothesis proposed to explain the occurrence and extent of avian host‐parasite co‐adaptation.

American Coot Parasitism on Least Bitterns

American Coots (Fulica americana) are known for laying eggs in the nests of conspecifics, but there is little evidence that they regularly parasitize the nests of other species. I found 13 Least Bittern (Ixobrychus exilis) nests, 2 of which were parasitized by coots. These are the first records of coots parasitizing Least Bitterns, and the first records of any form of brood parasitism on Least Bitterns. Nests of Least Bitterns also were parasitized experimentally with a variety of nonmimetic eggs and 27% were rejected (n = 11 nests). This indicates that Least Bitterns may possess some egg recognition abilities.

Egg Rejection in Marsh Warblers (Acrocephalus Palustris) Heavily Parasitized by Common Cuckoos (Cuculus Canorus)

AbstractIn the coevolutionary “arms race” between Common Cuckoos (Cuculus canorus) and their hosts, several adaptations and counter-adaptations have evolved. Here, we investigated natural parasitism and host sensitivity to egg rejection in Marsh Warblers (Acrocephalus palustris) in Bulgaria. The level of Common Cuckoo parasitism was high (28%), and average mimicry of Common Cuckoo eggs was good. Experimental parasitism with four egg-types that showed various degrees of mimicry of the host eggs revealed a generally high rejection rate of foreign eggs (37.5–100%). In addition, naturally laid Common Cuckoo eggs were rejected at a moderate rate (50%). The Marsh Warbler's ability to reject foreign eggs was strongly dependent on the degree of mimicry of the parasite egg but apparently not on differences in size between host and foreign eggs. Furthermore, intraclutch variation in host egg appearance was not related to the probability of egg rejection. The Marsh Warbler's highly developed egg-recognition ability and the good mimicry of Common Cuckoo eggs suggests that this poorly known host-parasite arms race has reached an advanced stage. The present study provides new insight into variables that are important for egg rejection in a heavily parasitized host population.Rechazo de Huevos en Nidos de Acrocephalus palustris Fuertemente Parasitados por Cuculus canorus

EGG REJECTION IN MARSH WARBLERS (ACROCEPHALUS PALUSTRIS) HEAVILY PARASITIZED BY COMMON CUCKOOS (CUCULUS CANORUS)

Abstract In the coevolutionary “arms race” between Common Cuckoos (Cuculus canorus) and their hosts, several adaptations and counter-adaptations have evolved. Here, we investigated natural parasitism and host sensitivity to egg rejection in Marsh Warblers (Acrocephalus palustris) in Bulgaria. The level of Common Cuckoo parasitism was high (28%), and average mimicry of Common Cuckoo eggs was good. Experimental parasitism with four egg-types that showed various degrees of mimicry of the host eggs revealed a generally high rejection rate of foreign eggs (37.5–100%). In addition, naturally laid Common Cuckoo eggs were rejected at a moderate rate (50%). The Marsh Warbler's ability to reject foreign eggs was strongly dependent on the degree of mimicry of the parasite egg but apparently not on differences in size between host and foreign eggs. Furthermore, intraclutch variation in host egg appearance was not related to the probability of egg rejection. The Marsh Warbler's highly developed egg-recognition ability...

Break-down of arms race between the red-backed shrike (Lanius collurio) and common cuckoo (Cuculus canorus)

AbstractThe red-backed shrike Lanius collurio once was parasitised by the common cuckoo Cuculus canorus in low frequency until the late 1960s in Hungary, but no case of parasitism is known from the last three or four decades. The cuckoo most probably abandoned this host species because its arms race had defeated, which may be indicated by the high level egg recognition and rejection ability of shrikes. However, mimicry of the cuckoo eggs in the last known cases of parasitism was significantly lower than between cuckoo eggs and host eggs collected from great reed warbler Acrocephalus arundinaceus nests within the same period. This suggests that red-backed shrikes won the arms race leaving no chance for cuckoos to develop better mimicry for their eggs. We tested these findings with experimentally induced parasitism using two types of real eggs: red-backed shrikes rejected 57.6% of the foreign conspecific eggs, but rejected 93.3% of the real cuckoo eggs transferred form nests of great reed warblers. This high level of rejection against real cuckoo eggs shows that there is no chance for presently occurring cuckoos to reparasitise red-backed shrikes in Hungary. Experimental eggs rejected by shrikes had lower mimicry than the eggs which were accepted, but intraclutch variation did not differ between accepters and rejecters. Hosts' aggression was significantly higher against the stuffed cuckoo than against the control species, the collared dove Streptopelia decaocto, and it was the least against female red-backed shrikes. Red-backed shrikes high aggression against cuckoo dummies also showed a highly developed antiparasite adaptation.

ADAPTATIONS BY GREAT REED WARBLERS TO BROOD PARASITISM: A COMPARISON OF POPULATIONS IN SYMPATRY AND ALLOPATRY WITH THE COMMON CUCKOO

Abstract Egg rejection behaviour, as an antiparasite defence against brood parasitism was compared in two great reed warbler Acrocephalus arundinaceus populations. In central Hungary the host population lives in sympatry with the common cuckoo Cuculus canorus, and it is heavily parasitised (ca 66%). In central Greece the great reed warbler occurs in allopatry with the cuckoo, so it is not parasitised at all. Experimental parasitism with poorly mimetic (often called 'non-mimetic') artificial cuckoo eggs revealed a 100% rejection rate towards the foreign eggs in the Greek population, but the Hungarian hosts accepted 29.4% and rejected 70.6% of the model cuckoo eggs. No other rejection type than ejection was observed. The significantly higher level of rejection in Greece than in Hungary suggests that the Greek great reed warbler population is an abandoned host population of the cuckoo, which kept its egg recognition ability. A computer-based image analysis of host's clutches revealed that interclutch variation in egg colour was greater than intraclutch variation in the Hungarian population, but not in the Greek population. Spottedness of eggs were similar in both populations. Generally, a tendency for a higher interclutch variation was found in Hungary. Intraclutch variation was more similar in the two populations, but for the colour variables it showed a lower value in Hungary than in Greece. The heavy cuckoo parasitism in Hungary is suggested to be the main cause for the increased interclutch variation in relation to intraclutch variation in egg appearance among great reed warbler clutches. The high interclutch variation reduces the chance that the parasite egg's appearance matches that of the hosts', which facilitates hosts' egg discrimination.

GENETIC AND GEOGRAPHIC VARIATION IN REJECTION BEHAVIOR OF CUCKOO EGGS BY EUROPEAN MAGPIE POPULATIONS: AN EXPERIMENTAL TEST OF REJECTER-GENE FLOW.

Host responses toward brood parasitism have been shown to differ among populations depending on the duration of sympatry between host and parasite, although populations not currently parasitized show rejection behavior against parasitic eggs. The persistence of rejection behavior in unparasitized host populations and rapid increases of rejection rate in parasitized ones have sometimes been explained as the result of gene flow of rejecter genes from sympatry to allopatry (rejecter-gene flow hypothesis). We present data on the rejection behavior of magpies (Pica pica) the main European host of the great spotted cuckoo (Clamator glandarius), in 15 populations (nine sympatric six allopatric) across their distribution range in Europe. Rejection rates of mimetic and nonmimetic model eggs were significantly higher in sympatric than in allopatric magpie populations, although differences in rejection rate of both mimetic and nonmimetic model eggs between magpie populations were significantly correlated even after controlling tor phylogenetic effects, with differences between sympatric and allopatric magpie populations being larger for mimetic than for nonmimetic model eggs. Differences in rejection of mimetic model eggs were related to both genetic and geographic distances between populations, but differences in rejection rate of nonmimetic model eggs were unrelated to these distances. However, when comparing only sympatric populations, differences in rejection rate of both mimetic and nonmimetic model eggs were related to geographic distances. A multiple autocorrelation analysis revealed that differences among populations in rejection rates of mimetic model eggs had a strong geographic component whereas the main component of rejection rate of nonmimetic model eggs was genetic rather than geographic. These results support the rejecter-gene flow hypothesis. We discuss differences in rejection rates of mimetic and nonmimetic model eggs that suggest the egg-recognition ability of the host is genetically based, but is affected by a learning process for fine tuning of recognition.

Rapid decline of host defences in response to reduced cuckoo parasitism: behavioural flexibility of reed warblers in a changing world

On Wicken Fen and nearby watercourses eastern England, parasitism by cuckoos, Cuculus canorus, declined from 26 and 16 of reed warbler (Acrocephalus scirpaceus) nests in 1985 and 1986, respectively...

Theory of intraspecific nest parasitism in birds

Abstract. The evolution of intraspecific nest parasitism is affected by egg recognition ability and clutch size. The coevolution of these three traits was analysed theoretically using a quantitative genetic model. Both multiple-nest parasites, which lay parasitic eggs in the nests of many hosts, and single-nest parasites, which lay in the nest of a single host, were analysed. The model predicts the following. (1) Brood parasitism evolves when the competition intensity among offspring in a nest, s, is larger than the parasitism cost, n. (2) The optimal parasitism rate, p* , the optimal recognition rate, r*, and the optimal clutch size, E*, increase with s/n. (3) r* , p* and E* are larger for multiple-nest parasites than for single-nest parasites. (4) The number of eggs laid in a female's nest is the same as the optimal clutch size without parasitism, Ê. (5) The optimal clutch size, E*, and the sum of the nest owner's eggs and the parasitic eggs in a nest, i.e. (1 - p*)E* + (l - r* )p*E*, are larger than Ê .

Relative Importance of Parasitism by Chrysococcyx Cuckoos versus Conspecific Nest Parasitism in the Northern Masked Weaver Ploceus taeniopterus

In a 3-year study of the Northern Masked Weaver Ploceus taeniopterus in Kenya, I determined that fewer than 1% of the nests of this species had been parasitized by Chrysococcyx cuckoos. This rate of heterospecific parasitism is low when compared with the rate of parasitism by conspecifics, and I conclude that heterospecific nest parasitism has been a relatively unimportant factor in selecting for egg-color variability and egg-recognition ability in Ploceus weavers. I show that I could readily distinguish cuckoo eggs from weaver eggs, and I discuss the circumstances surrounding the six known or suspected cases of cuckoo parasitism that I detected.