Explicit experimental evidence for the role of mate guarding in minimizing loss of paternity in the Seychelles warbler

Extra-pair copulations (EPCs) (copulations outside the pair bond) resulting in extra-pair fertilizations (EPFs) are widespread in birds. To increase reproductive success, males should not only seek EPCs, but also prevent their females from having EPFs. Male Seychelles warblers (Acrocephalus sechellensis) follow their partner closely during the period when these females are most receptive (fertile period). The Seychelles warbler is the first species to offer explicit experimental evidence that mate guarding functions as paternity guarding: in territories where free-living males were induced to stop mate guarding during the pair female''s fertile period, the rates of intrusions by other males and successful EPCs (male mounting female) were significantly higher than those observed in the control group and in the absence of mate guarding the frequency of successful EPCs increased significantly with local male density. Male warblers do not assure their paternity through frequent copulations to devalue any sperm from other males: males do not copulate with their partners immediately following a successful EPC obtained by their partners, the frequency of successful within-pair copulations does not increase with the frequency of successful EPCs and females initiate all successful copulations and are capable of resisting copulation attempts.     

Testosterone, cuckoldry risk and extra-pair opportunities in the Seychelles warbler

In male birds, testosterone (T) plays an important role in aggressive and mate-attraction behaviour. In the cooperatively breeding Seychelles warbler, Acrocephalus sechellensis, extra-group copulations (EGCs) occur frequently, but are not accompanied by sexual courtship displays as in within-pair copulations. Paternity is nearly always gained by primary males. We investigated whether T levels and sperm storage capability (cloacal protuberance (CP)) in adult primary and subordinate males were related to timing of egg laying, levels of cuckoldry and extra-group paternity (EGP) opportunities. During the sexually active period before egg laying, T levels and CP were only elevated or enlarged (respectively) in primary males, and some suggestion was found that subordinate males do not invest in elevated T levels. The peak in T occurred during the fertile period of the female partner and corresponded to the peak period of male sexual displays and mate guarding, but was independent of cuckoldry risk (density of neighbouring primary males). CP was also enhanced during this period; however, CP but not T remained elevated after egg laying by their mates, and CP but not T was positively related to EGP opportunities (density of neighbouring fertile females). We conclude that T is involved in sexual courtship displays and mate guarding, but not in gaining EGCs. These findings contrast with those in other species where EGP involves elaborate sexual displays.     

Mate guarding in the Seychelles warbler is energetically costly and adjusted to paternity risk

Males may increase their fitness through extra-pair copulations (copulations outside the pair bond) that result in extra-pair fertilizations, but also risk lost paternity when they leave their own mate unguarded. The fitness costs of cuckoldry for Seychelles warblers (Acrocephalus sechellensis) are considerable because warblers have a single-egg clutch and, given the short breeding season, no time for a successful replacement clutch. Neighbouring males are the primary threat to a male's genetic paternity. Males minimize their loss of paternity by guarding their mates to prevent them from having extra-pair copulations during their fertile period. Here, I provide experimental evidence that mate-guarding behaviour is energetically costly and that the expression of this trade-off is adjusted to paternity risk (local male density). Free-living males that were induced to reduce mate guarding spent significantly more time foraging and gained significantly better body condition than control males. The larger the reduction in mate guarding, the more pronounced was the increase in foraging and body condition (accounting for food availability). An experimental increase in paternity risk resulted in an increase in mate-guarding intensity and a decrease in foraging and body condition, and vice versa. This is examined using both cross-sectional and longitudinal data. This study on the Seychelles warbler offers experimental evidence that mate guarding is energetically costly and adjusted to paternity risk.     

Age-Related Variation in Mate-Guarding Intensity in the Bluethroat (Luscinia s. svecica)

Female extra‐pair copulations (EPCs) have selected for male paternity guarding strategies in many bird species. In the bluethroat, Luscinia s. svecica, males guard their mates closely during the last 2 d before the start of egg laying, but there is great individual variation in the intensity of mate guarding. Here we show that some of this variation is related to male age. Old males guarded their mates with much lower intensity and sang more than young males, although the latter difference was not statistically significant. Controlling for male age, male and female coloration and size were not significantly related to the intensity of mate guarding. We have previously shown that young and old males had a similar paternity loss in their own broods. On the other hand, old males were far more successful than young males in achieving extra‐pair fertilizations. These patterns suggest that young and old males have different trade‐offs between preventing paternity loss in own nest and gaining paternity in others, because male skills in obtaining EPCs improve with experience and/or because of female preferences for old males as copulation partners. There were no significant relationships between paternity and male mate‐guarding behaviour during the fertile period, indicating that mate guarding is not a very effective paternity‐assurance strategy in the bluethroat.     

Sperm transfer, sperm storage, and sperm digestion in the hermaphroditic land snail Succinea putris (Gastropoda, Pulmonata)

Abstract. Many hermaphroditic species are promiscuous, have a sperm digesting organ and an allosperm storage organ (i.e., spermatheca) with multiple compartments (i.e., spermathecal tubules) providing opportunities for sperm competition. The relative paternity of a sperm donor drives the evolution of mating behaviors that allow manipulation of the sperm receiver's reproductive behavior or physiology. We studied the relationship between sperm transfer, sperm storage, sperm digestion, and copulation duration in the hermaphroditic land snail Succinea putris , in which an active individual mates on top of a passive individual. Specifically, we examined (i) whether the entire copulation duration was required to complete reciprocal sperm transfer, (ii) sperm transfer patterns and their relationship with activity role, and (iii) the timing of sperm storage and sperm digestion. We found that reciprocal sperm transfer was completed within the first 5 h of copulation, which is ∼2–3 h before the end of copulation. Sperm transfer was mainly sequential, meaning that one individual donated all his ejaculate before its partner started to reciprocate. The initiation of sperm transfer did not depend on the activity role. The presence of allosperm in the spermatheca before sperm transfer suggests that individuals remate before they are allosperm depleted. No sperm was digested during copulation but sperm digestion took place 0–72 h after copulation. Our results suggest that contact mate guarding is a likely manipulation strategy in S. putris , because partners cannot immediately remate. In addition, staying in copula after sperm transfer is completed seems to prevent the immediate digestion of sperm and therefore may promote sperm displacement and allosperm storage.     

Territorial intrusions and copulation patterns in red kites, Milvus milvus, in relation to breeding density

Two main paternity assurance strategies are generally found in birds: mate guarding and frequent copulations. The latter is expected particularly in species such as raptors that cannot guard their mates efficiently because of ecological constraints, such as frequent courtship feeding. I investigated the prelaying behaviour of red kites, in which the males courtship feed. I compared pair behaviour in situations of varying breeding density and simulated male territorial intrusions by presenting decoys. Males' certainty of paternity was likely to decrease with increasing breeding density, because of the proximity of other males and more frequent male territorial intrusions during the presumed fertile period. The percentage of time spent by males within their breeding territory during the prelaying period was positively related to the number of close breeding neighbours, suggesting territory surveillance and mate guarding. The kites copulated frequently and over a long period. Copulation frequency prior to and during laying increased with breeding density, and in isolated pairs in response to simulated male territorial intrusions. The results support the idea of paternity assurance through frequent copulations during the presumed fertile period of the female, and suggest that early copulation activity is related to functions other than fertilization, such as pair bonding or mate assessment. Copyright 2000 The Association for the Study of Animal Behaviour.     

Female collared flycatchers choose neighbouring and older extra‐pair partners from the pool of males around their nests

Extra‐pair copulation is common among passerine birds. Females might engage in this behavior to obtain direct or indirect benefits. They may choose extra‐pair males with larger ornaments, especially if they are costly to produce. Here we studied extra‐pair paternity in the collared flycatcher. Genetic analysis allowed us to identify the presence or absence of extra‐pair young in the focal nests, and to identify extra‐pair fathers. We also identified potential males available as extra‐pair sires around the nests of females who had extra‐pair young. First, we tested the relationship between paternity in own nest and ornament size (wing patch and/or forehead patch), morphological traits and age of social males and females. Second, we compared the same suite of traits among social mates, extra‐pair males and all potential extra‐pair mates. Finally, we investigated the effect of the size of ornaments on the distance between the social nest and that of nest the extra‐pair father. Contrary to our prediction, males with larger ornaments and longer wings lost more paternity in their nests. We also found that early breeders lost less paternity in their nests. Extra‐pair males were older and had longer wings than social and potential extra‐pair males. Females mainly obtained extra‐pair mates near their nests but the distance did not vary according to ornamentation. These results could potentially be explained by differences in mate guarding strategy as older males may be more experienced in guarding their mate and attract other females more easily. More data about mate guarding and prospecting are needed to increase our understanding of mechanisms underlying the extra‐pair paternity in birds.     

Factors influencing mate guarding and territory defence in the stitchbird (hihi)

Socially monogamous male birds are predicted to maximise their reproductive success by pursuing extra-pair copulations (EPCs) while engaging in anti-cuckoldry behaviour such as mate guarding. In the stitchbird, Notiomystis cincta, high levels of forced EPCs and a high proportion of nestlings resulting from extra- pair fertilisations lead to the prediction that males of this species should exhibit intense paternity guarding behaviours. While studying an isolated stitchbird population on Tiritiri Matangi Island New Zealand (3636'S, 17453'E), I collected daily behavioural data throughout the breeding season from 15 males in 2000/01 and 27 males in 2001/02. In this study, male stitchbirds demonstrated clear paternity guarding by exhibiting: (1) an increased likelihood of being close to their mate during her fertile period, (2) an increased initiation of mate contact during her fertile period, (3) switching from site-specific territorial defence during the pre-fertile period to defending an area centring on the their female partners location during her fertile period, and (4) an increased following of the female to communal feeding sites outside the territory during her fertile period. For polygynous males, mate guarding and territorial defence were conditional on which of their females was fertile. Additional evidence supporting the hypothesis that mate guarding in this species is a form of paternity assurance, rather than protection from harassment, is that males protected their partner from harassment by other stitchbird males but did not intervene when females were harassed by male bellbirds, Anthornis melanura. While mate-guarding intensity in many species is conditional on the stage of female fertility, male stitchbirds also modified their behaviour depending on the location of the female and the rate of intrusions by extra-pair males. Resident males adopted a best-of-a-bad-job tactic when they were unable to locate their female by defending an area around her last known location. Furthermore, when the rate of intrusions by extra-pair males increased they traded-off the area they could defend within their territory against their ability to guard the female. Territory takeovers were uncommon, but when they did occur older males displaced younger males and healthy birds displaced sick ones. Contrary to the prevailing view that mate guarding is a male response to female infidelity, male stitchbirds appear to use mate guarding primarily to prevent paternity losses from forced EPCs. Future assessments of mate guarding function should consider the possibility that mate guarding involves a combination of conflict and co-operation between the sexes.     

Mate guarding and frequent copulation in birds: A meta‐analysis of their relationship to paternity and male phenotype

In many birds, males are presumed to protect their paternity by closely guarding their mate or copulating frequently with her. Both these costly behaviors are assumed to reduce the risk and/or intensity of sperm competition. However, despite many studies on avian extra‐pair paternity, it remains unclear how strongly these behaviors are related to fitness and other key life‐history traits. Here, we conduct meta‐analyses to address two questions. First, are mate guarding and/or frequent copulation positively correlated with a male's share of paternity at his nest? We find a significant positive correlation between both presumed paternity protection behaviors and paternity share. The relationship is, however, weak (r = 0.08–0.23). This is perhaps unsurprising if the risk of partner infidelity, hence the need to protect paternity, varies among males. For example, more attractive males might have less need to protect their paternity. Second, do males with higher indices of so‐called male “quality” (phenotypic measures, usually subjectively defined by researchers as predictors of male attractiveness) exhibit lower levels of paternity protection behavior? We find a negative correlation between male quality and paternity protection. This finding might partly explain the weak relationship between paternity protection and paternity, although we discuss other, nonmutually exclusive possibilities.     

Mate guarding and sperm displacement in the water strider Gerris lateralis Schumm. (Heteroptera: Gerridae)

SUMMARY. 1. Field and laboratory observations on the mating behaviour of Gerris lateralis Schumm. allowed three distinct phases to be distinguished: (i) a precopulatory phase (1.5min, SD=1.3), (ii) copulation (16.2min, SD=12.9), and (iii) a postcopulatory phase. The duration of the postcopulatory phase, during which the male rode passively on the back of the female without genital contact, varied considerably (11 min to > 48h). Females appeared reluctant in all matings, and matings were forced by males.
2. Laboratory experiments showed that the females were able to store sperm for more than 30 days without decrease in fertilization rate. In double mating experiments, where partially sterilized males were used, it was demonstrated that sperm displacement was extensive. The last male to mate fertilized approximately 80% of the eggs.
3. It is concluded that the postcopulatory behaviour is beneficial to males in terms of paternity assurance, and it is interpreted as a mate guarding behaviour.     

Copulation behaviour in mammals: evidence that sperm competition is widespread

We review information on copulation behaviour and sperm competition in mammals using data primarily from the literature. Female mammals of many species regularly copulate with more than one male during each oestrous period. Such multi-male copulations are reported more often in social, compared with solitary species. In addition, the mates of males of polygynous species experience multi-male copulations as often as the mates of males or monogamous species. Male mammals attempt to increase their certainty of paternity through a number of reproductive tactics. Copulation frequency is higher in specks with multi-male copulations compared with other species. Consortships, which can br regarded as a form of mate guarding, are often absent from species in which more than one male copulates with each female during her oestrous period. Most solitary burrow-living small mammal species copulate in the open, whereas social species often copulate inside their burrows. Insurance copulations may occur in many species since high copulation rates occur in four circumstances: (i) when mates are reunited, (ii) when a new male takes over a female, (iii) when a strange male steals a copulation, and (iv) when an audience of males is present.     

Mate switching and copulation behaviour in King Penguins

Extra‐pair paternity (EPP) in monogamous birds may result from either extra‐pair copulations (EPCs) or mate switching. In this study of King Penguins in South Georgia, we observed no EPCs at all, an effect of very efficient mate guarding. Onshore males fast and need not divert attention to foraging or to defending nest or territory, as this species has neither. However, we found that mate switching was common. On average 38% (range: 29%–56%; three years pooled) of the birds established pair bonds with at least one initial partner before switching to the partner they bred with (i.e. the “pair mate”). Of the observed copulations of 44 studied females, 22% were with initial partners and 78% with the pair mate. This and the high proportion of mate switching suggest that roughly 10% of the females could have received sperm from males other than the pair mate. The average copulation frequency was 0.026 h^?1, resulting in an estimated 8.2 copulations per clutch (which consists of one egg). That more copulations than necessary for fertilisation occur suggests that males try to protect paternity by sperm competition, and that this is a result of the potential for EPP due to mate switching in King Penguins. All observed copulations except one took place between days 13 and 5, with the peak 7.5 days prior to egg‐laying. The birds found their pair mates (often not the same as in the previous year) on average about 10 days before egg‐laying, and always established themselves at the outskirts of the colony about 8 days before egg‐laying. Thus, most copulations occurred around the time the birds joined the colony. We suggest that it is adaptive to obtain a breeding spot early, because the colony will grow and pairs joining later will protect the offspring. Additionally, we suggest that early copulation outside the colony is adaptive because of the risk of failing to fertilise the egg when copulating among aggressive neighbours inside the dense colony. Based on these two arguments we suggest a “safe place hypothesis” to explain the early copulation peak in King Penguins.     

Pattern of sperm transfer in redback spiders: implications for sperm competition and male sacrifice

Many sperm competition studies have identified copulation durationas an important predictor of paternity. This result is ofteninterpreted as a sperm transfer effect—it is assumed thatsperm transfer is limited by copulation duration. Here we testthe assumption of duration-dependent sperm transfer in the Australianredback spider, Latrodectus hasselti, in which a correlationbetween copulation duration and paternity has been implicatedin the evolution of a rare male self-sacrifice behavior. Maleredbacks facilitate sexual cannibalism by females during copulation.Sexual cannibalism is apparently adaptive for redback males,in part because it results in longer copulations (25 versus11 min.), and copulation duration is positively correlated withpaternity. We assessed sperm transfer in normal copulationsand in copulations that we terminated at 5, 10, or 20 min. Ourresults show that the paternity advantage of sexual cannibalismis not owing to time-dependent sperm transfer, as redback malestransfer the majority of their sperm within the first 5 minof copulation. This suggests that the link between copulationduration and paternity may instead be owing to cryptic femalechoice or the transfer of nongametic ejaculatory substances.Results further indicate that the act of cannibalism itselfmight play a role in mediating sperm transfer. This study highlightsthe importance of understanding mechanisms of sperm transferwhen attempting to interpret the outcome of sperm competitionstudies.     

Male copulation behaviour and the risk of sperm competition

When females mate with more than one male during their reproductive cycle, males may increase their share of paternity by copulating repeatedly with the same female. Accordingly, males should mate repeatedly with the same female more frequently when the risk of sperm competition is greater. We examined this idea experimentally in the orb-web spiderNephila edulis , which is characterized by both extreme sexual size dimorphism and extreme male size variation. Comparison of the mating behaviour of solitary and pairs of males on the webs of virgin and mated females revealed that males adjust the frequency and duration of copulation according to the mating history of the female and the presence of rival males. Males copulated more frequently and for longer with virgin than mated females. The copulation behaviour of males in the presence of rivals depended upon their relative size. Typically, larger males prevented smaller rivals from gaining access to the female and therefore were able to copulate more frequently. Smaller males copulated less frequently, but for longer periods, which may have increased their share of paternity. The size of male N. edulis can vary by an order of magnitude, and our results suggest that this variation may be maintained by the alternative size-dependent strategies of preventing or winning sperm competition. Copyright 2003 Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour.      

Timing of sperm transfer in Diacamma pallidum

Abstract.  Diacamma species (Hymenoptera, Formicidae) differ from other ants by the extremely long duration of copulation. By using histological sections through mating pairs of Diacamma pallidum (F. Smith), it is demonstrated that the transfer of sperm to the female genital tract only takes 2 min and is completed quickly after the onset of copulation, although the male and female will remain connected for many hours. Next to the two traditional hypotheses of mate guarding and mate manipulation commonly invoked to explain prolonged copulations, a new hypothesis is proposed linked to the interference of the nestmate workers with the mating pair, and suggestions for further research are given.     

Biases in sperm use in the mallard: no evidence for selection by females based on sperm genotype

If we are to understand fully the factors influencing fertilization success, it is essential to untangle male and female effects on sperm use. In many species, differences in fertilizing ability have been found between males or male genotypes, but the impact of female effects is less clear and may vary between taxa. Here, we examine sperm use in the mallard (Anas platyrhynchos), a species of bird in which forced copulation forms a major component of the mating system, to investigate whether there is any evidence for post-insemination female choice or rejection of particular sperm genotypes. Current models of sperm use in birds suggest observed patterns of paternity are a result of passive sperm loss from the reproductive tract and the relative timing of inseminations. Although this type of model successfully predicted average values of last male precedence observed in this species, there was considerable variation between females in their pattern of sperm use, with a tendency for females to use sperm of a single genotype. However, females did not consistently prefer one genotype over another in repeated inseminations with identical sperm mixtures, suggesting that post-insemination female preference based on sperm genotype did not account for this variation.     

Explicit experimental evidence for the effectiveness of proximity as mate-guarding behaviour in reducing extra-pair fertilization in the Seychelles warbler

Extra-pair copulations (EPCs; copulations outside the pair bond) are widespread in birds and may result in extra-pair fertilizations (EPFs). To increase reproductive success, males should not only seek to gain EPFs, but also prevent their own females from gaining EPFs. Although males could reduce the number of EPCs by their mates, this does not necessarily mean that they reduce the number of EPFs; indeed several studies have found no association between EPCs and EPFs. Male Seychelles warblers (Acrocephalus sechellensis) follow their partner closely during the period when the pair female is most receptive (fertile period). We show that males that guarded their mates more closely were less likely to have extra-pair young in their nest. This study on the Seychelles warbler is the first to provide explicit experimental evidence that mate guarding is effective in reducing EPFs. First, in territories where free-living males were induced to stop mate guarding during the pair female's fertile period, extra-pair parentage was higher than in the control group. Second, in the experimental group, the probability of having an extra-pair nestling in the nest was positively associated with the number of days during the fertile period for which mate guarding was artificially stopped. Thus, male mate guarding was effective in reducing the risk of cuckoldry.     

Decoy presentations as a means to manipulate the risk of extrapair copulation: an experimental study in a semicolonial raptor, the Montagu's harrier (Circus pygargus)

Mate guarding and frequent copulations are two alternative paternity assurance strategies found in birds. In species with intensecourtship feeding, like raptors, the "frequent copulation"strategy is expected because male food provisioning conflictswith mate guarding. We evaluated experimentally the paternityassurance behavior of a semicolonial raptor, the Montagu'sharrier Circus pygargus, using decoy presentations to simulateterritorial intrusions. Breeding pairs were exposed to maleand female decoys at different periods during the female's reproductive cycle. Agonistic responses to decoys were intra-sexual,and the timing and intensity of male attacks toward male decoyssupported responses related to the risk of extrapair copulation(EPC): Male aggression peaked during the presumed fertile periodand almost disappeared after clutch completion. During thefertile period, copulation rate was significantly higher, andcopulations lasted longer, during male decoy presentations than during controls. Males also spent more time close to the femaleduring male decoy presentations compared to controls, bothduring the early prelaying and fertile periods, but not duringincubation. In the fertile period, males also increased presencetime close to the female in the hour following the removal of the male decoy. Conversely, female decoy presentations hadno significant effect on copulatory behavior or male presencetime. These results showed that the risk of EPC can be experimentallymanipulated by the means of decoy presentations, simulatingmale territorial intrusions, and that male Montagu's harriersincrease their short-term copulation frequency and female surveillancewhen they perceive themselves at an increased EPC risk.     

Competing for last place: Mating behaviour in a pill-box crab, Halicarcinus cookii (Brachyura: Hymenosomatidae)

The mating strategy of Halicarcinus cookii was investigated to ascertain how males maximised their fitness through mate choice. An intertidal population at Kaikoura, New Zealand, was dominated by mature crabs of both sexes in summer and by immature crabs in the colder months. More than 95% of mature females were ovigerous with early stage and late stage broods found in almost every month, indicating that egg production and larval release is continuous. The operational sex ratio was less than 1 male/female in summer, but often more than 1.0 in the colder months. The gonosomatic index increased along with brood development so that as soon as zoeae were released, the next clutch of eggs was ready to be fertilised. Males searched for receptive females and began pre-copulatory mate guarding without any courtship display. They mated preferentially with late stage or non-ovigerous females: copulation duration was longest for stage 5 females as was post-copulatory guarding (mean 18.3 h). Late stage females were up to 14% of the female population. Mate attraction seems to be the result of an ovarian signal rather than from the developing brood. Manipulation of the sex ratio had effects upon copulation duration and post-copulatory guarding: presence of a rival male increased duration of guarding. Females showed precocious mating in the penultimate instar and were able to lay fertilised eggs after their pubertal moult in the absence of males. H. cookii females have many mates, but males attempt to ensure paternity by preferentially pursuing mature females close to egg laying and by guarding these females after copulation. These behaviours are all elements of a competitive strategy to ensure that a male loses (not wins) the race to copulate because females have a ventral seminal receptacle, giving sperm precedence to the last male to mate. Male mating behaviour is a consequence and evolutionary response to female morphology.     

Brutzeitliches Verhalten von Seggenrohrs?ngernAcrocephalus paludicola in der Voliere

Zusammenfassung Das Brutverhalten handaufgezogene Seggenrohrsänger wurde bei 14 Brutversuchen untersucht. Die frühen Stadien des Brutgeschäftes dieser Art konnten im Freiland bisher nicht beobachtet werden. Zwei Weibchen bauten ihr Nest in 3–5 Tagen, am häufigsten morgens und abends. Die Nestbautätigkeit wirkte als starker Stimulus auf die Kopulationsbereitschaft zweier Männchen. Jedes von ihnen versuchte während der fertilen Periode der Weibchen permanent zu kopulieren. Die Weibchen wehrten die allermeisten Kopulationsversuche ab oder versteckten sich in der Vegetation. Die Kopula war ungewöhnlich lang (¯x = 23,7 ± 11,8 min; n=31), weil die Männchen zwischen aktiven Phasen (Kloakenkontakt) auf dem Rücken der Weibchen oder direkt hinter ihm sitzen blieben. Die Bebrütungsdauer bis zum Schlupf betrug zweimal 12 und einmal 14 Tage. Der Abstand zwischen Gelegeverlust und Ablage des 1. Eies des nächsten Geleges betrug 7 Tage (Median; n=7). Bei schwierig im Freiland zu beobachtenden Arten wie dem Seggenrohrsänger können Volierenbeobachtungen entscheidend zum Verständnis deren Biologie beitragen.

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Reproductive behaviour of Aquatic WarblersAcrocephalus paludicola in captivity

Breeding behaviour of four hand-raised Aquatic Warblers has been studied in captivity. Two females produced fourteen clutches in 1991–94. The behaviour of early stages of the breeding cycle of this promiscuous sylviid warbler, which is one of the rarest passerine birds in the western Palearctic, could never been observed in the wild up to now. Both females built their nests within 3–5 days, being most active during early morning and in the evening. Nestbuilding strongly stimulated the copulation activity of two males. Each of the two males continuously attempted to copulate with the females during their fertile periods. Both females repulsed almost all of the copulation attemps and hit in the vegetation. The duration of mountings was unusually long (¯x = 23.7 ± 11.8 min; n=31). Between cloacal contacts the male remained on top or directly behind the female. Incubation (from laying of the last egg until hatching of first young) lasted 12 (two cases) and 14 days (one case). The interval between loss of a clutch and laying the first egg of the next clutch was 7 days (median; n=7). In case of a secretive and unobtrusive species being hard to observe in the wild like the Aquatic Warbler, studies of captive birds can provide an effective tool to understanding important aspects of their biology.