Extra-pair Copulation Attempts Research Articles

How do colonial Eurasian Griffon Vultures prevent extra-pair mating?

In colonial breeding species, preventive measures to reduce the risks of extra-pair copulations (EPCs) should reflect the actual risk perceived by males (e.g., proximity of neighbors, intrusions into the nest) mainly during the fertile period. In colonial vultures, specific studies examining the preventive measures that minimize the risks of EPCs occurring within the competitive context of colonial breeding have not been conducted. Here we tested at Eurasian Griffon Vulture (Gyps fulvus) nesting sites the intensity of paternity assurance behavior, shown as frequency and duration of within-pair copulations (WPCs), potential mate vigilance or nest attendance, and levels of aggressivity. This was measured according to the frequency of territorial intrusions and comparison of the fertile vs. the non-fertile period. Our findings suggest that the frequency of WPCs and their duration increased significantly during the presumed fertile period, regarded as the period when Griffon pairs spent significantly more time together at their nests. In addition, low levels of territorial intrusions were observed, an aggressive response of pairs towards intruders, and a relatively high presence of pairs at the nests during the fertile period. Thus, although nesting sites are subject to low exposure to EPC attempts, the increased frequency and duration of copulations during the fertile period suggests that, under pressure from the colonial breeding system, a higher rate of copulations is the most effective preventive mechanism against relative uncertainty of paternity.

Extrapair Copulations Predict Extrapair Fertilizations in the American Crow

Abstract. The general relationship between extrapair copulations (EPC) and extrapair paternity (EPP) in wild birds is unclear because relatively few studies have collected both types of information from a single population. I compared observed copulatory behavior with genetic paternity in a population of the American Crow (Corvus brachyrhynchos). For each group of nesting crows, the proportion of extrapair young in a brood was higher when EPC attempts were observed in the group that year. The overall proportion of broods with extrapair young was identical to the proportion of focal group-years in which EPC attempts were observed (32%). In a given brood, however, observed EPC attempts did not always predict EPP, and failure to observe EPCs did not always predict monogamy. Furthermore, males observed attempting EPCs often differed from the males gaining EPP, suggesting that EPCs were attempted by multiple males with certain females in certain years. Observed EPC attempts were initiated by males, and most ap...

Extrapair copulations are frequent but unsuccessful in a highly colonial seabird, the little auk, Alle alle

Sperm competition theory predicts that colonially breeding birds, such as many seabirds, should be exposed to high risks of sperm competition because there are many potential mating partners and severe socioecological constraints on mate-guarding behaviour. However, parentage studies have usually revealed a low frequency of extrapair paternity in colonial seabirds. Detailed studies of copulation behaviour could provide valuable insights into the causality of genetic monogamy in these species. We investigated the timing, frequency and success of extrapair and within-pair copulation attempts in the little auk, a socially monogamous and highly colonial seabird that raises only a single chick per year. We found that the majority of monitored individuals (above 60% in both sexes) engaged in extrapair copulation activities. Extrapair copulation attempts made up usually more than 10% of all copulation attempts of a particular individual but were generally unsuccessful because of female rejection behaviour. Only 2% (8/330) of all copulations with cloacal contact were extrapair copulations. Molecular parentage analysis of 64 chicks revealed only two cases of extrapair paternity, which is comparable to the proportion of successful copulations that were extrapair. We conclude that genetic monogamy seems to be maintained at a proximate level through female resistance to male extrapair copulation attempts and frequent within-pair copulations. Nevertheless, not all extrapair copulations were rejected by females, which suggests that engaging in one or a few extrapair copulations could be adaptive to females, for example as an insurance against mate infertility.

VIGILANCE BEHAVIOR IN THE HARLEQUIN DUCK (HISTRIONICUS HISTRIONICUS) DURING THE PREINCUBATION PERIOD IN LABRADOR: ARE MALES VIGILANT FOR SELF OR SOCIAL PARTNER?

Abstract Males of several avian species are more vigilant than their female partners, particularly during the preincubation period. Male vigilance may function as a deterrent of extrapair copulation attempts (EPCs) or to ensure male survival, because males of sexually dimorphic species may be more conspicuous to predators than females. However, vigilant males may act as antipredator sentinels to enhance female survivorship, which may also allow females to feed and rest more efficiently, thereby enhancing their ability to form clutches. We attempted to distinguish between the “male benefits” and “female benefits” hypotheses by studying the behavior of unpaired males and paired Harlequin Ducks (Histrionicus histrionicus) during the preincubation period. Paired males were, on average, four times more vigilant than unpaired males and their mates, which suggests that elevated levels of vigilance by paired males does not function primarily for self-protection against predators. Males were not more vigilant duri...

Vigilance Behavior in the Harlequin Duck (Histrionicus Histrionicus) During the Preincubation Period in Labrador: Are Males Vigilant for Self or Social Partner?

AbstractMales of several avian species are more vigilant than their female partners, particularly during the preincubation period. Male vigilance may function as a deterrent of extrapair copulation attempts (EPCs) or to ensure male survival, because males of sexually dimorphic species may be more conspicuous to predators than females. However, vigilant males may act as antipredator sentinels to enhance female survivorship, which may also allow females to feed and rest more efficiently, thereby enhancing their ability to form clutches. We attempted to distinguish between the “male benefits” and “female benefits” hypotheses by studying the behavior of unpaired males and paired Harlequin Ducks (Histrionicus histrionicus) during the preincubation period. Paired males were, on average, four times more vigilant than unpaired males and their mates, which suggests that elevated levels of vigilance by paired males does not function primarily for self-protection against predators. Males were not more vigilant during the female’s fertile period, contrary to the “paternity assurance” hypothesis. Male vigilance during feeding bouts was highest when pairs fed alone near shore—a condition in which feeding was likely more “risky.” Male vigilance was positively correlated with female feeding when females fed near shore, but not at other times. During resting bouts, males were vigilant 14 ± 0.01% of the time in all conditions. We suggest that male vigilance may be important to enhance female survival, especially when females feed under risky conditions.Comportement de Vigilance chez Histrionicus histrionicus durant la Période de Pré- incubation au Labrador: Les Mâles Sont-ils Vigilants pour Eux-mêmes ou pour leur Partenaire Social?

Extra‐pair paternity in the Lesser Kestrel Falco naumanni: a re‐evaluation using microsatellite markers

Modern molecular techniques based on DNA typing have revolutionized our view of avian mating systems. Birds were considered to be essentially monogamous only a few years ago (Lack 1968). In contrast, Griffith et al . (2002) have recently summarized how molecular techniques have revealed that birds are only rarely monogamous, with extra-pair offspring found in approximately 90% of the species studied to date. It has been known for some time that individuals in supposedly monogamous species often adopt a mixed reproductive strategy (Trivers 1972). Both males and females may seek extra-pair copulations (EPC), which could provide them with some genetic benefits (for a review of benefits and drawbacks of engaging in EPC, see Birkhead & Moller 1992; Wink & Dyrcz 1999). Although there is great interest in the reasons for differences in extra-pair paternity (EPP) rates in birds, few studies have compared the results obtained by different molecular techniques. Among available markers, DNA fingerprinting in the 1990s and, more recently, microsatellites, are the most popular in elucidating genetic relationships in birds (Burke & Bruford 1987, Ellegren 1992), but, to our knowledge, comparisons of the performance of these two techniques using the same sample sets have not been reported. In this study, we reappraised EPP in the Lesser Kestrel Falco naumanni . Our aim was to recalculate levels of EPP in this species using microsatellite markers instead of DNA fingerprinting, and to compare the results obtained with both techniques. Earlier studies of the copulatory behaviour of Lesser Kestrels (Negro et al . 1992) have already shown that some males pursue a mixed reproductive strategy, with a 6.7% incidence of EPC attempts, and DNA fingerprintings of 26 families revealed that 3.4% of the nestlings resulted from extra-pair fertilizations (Negro

Mark-recapture and behavioral ecology: a case study of Cliff Swallows

Mark–recapture and the statistical analysis methods associated with it offer great potential for investigating fitness components associated with particular behavioral traits. However, few behavioral ecologists have used these techniques. We illustrate the insights that have come from a long–term mark–recapture study of social behavior in Cliff Swallows (Petrochelidon pyrrhonota). The number of transient swallows passing through a colony per hour increased with colony size and was responsible in part for increased rates of ectoparasite introduction from outside the group into the larger colonies. Annual survival probabilities of males engaging in extra–pair copulation attempts were lower than those of males not seen to commit extra–pair copulations, suggesting that males who engage in this behavior may be inferior individuals and that females do not benefit from copulating with them. Females engaging in intraspecific brood parasitism had higher annual survival probabilities than ones either parasitized by others or not known to be either hosts or parasites. This suggests that parasitic females are high–quality birds and that brood parasitism is an effective reproductive tactic for increasing their fitness. By estimating first–year survival of chicks, we found that a clutch size of 4 eggs is often the most productive, on average, as measured by recruitment of offspring as breeders, although birds laying the more uncommon clutch size of 5 fledge more young on average. This helps to explain the observed clutch–size distribution in which clutch size 4 is the most commonly produced.

Extrapair paternity in the common sandpiper, Actitis hypoleucos, revealed by DNA fingerprinting

The prevalence of extrapair paternity in many socially monogamous passerines has not been mirrored in most monogamous nonpasserines studied to date. Here, we investigated the reproductive behaviour of a socially monogamous shorebird, the common sandpiper, using multilocus DNA fingerprinting. Given the high level of paternal care in the species, and the likely high costs in allocating care between kin and nonkin in species with precocial young, we predicted low levels of extrapair paternity similar to other monogamous shorebirds. We found the social mating system to be predominantly monogamous although one polyandrous pairing was identified. Of 83 offspring from 27 broods, 13 (15.7%) young from five (18.5%) broods were identified as being extrapair. There was no evidence of intraspecific nest parasitism or quasiparasitism. In this population, territorial intrusions were carried out largely by males but did not appear to be related to seeking extrapair copulations (EPCs). Seventy copulation attempts were observed and most were within-pair (84%). Six of eight EPC attempts occurred outside the territory of the female's social mate. Copulation rates were significantly higher just before and during egg laying than at other times during the study. At least two females that reared extrapair young had associated with males other than their eventual mates on arrival, suggesting that some females use rapid mate switching as a mating tactic, facilitated perhaps by the asynchronous arrival among both sexes in this population. Why some female sandpipers mate promiscuously remains unresolved.

Female mate preferences and subsequent resistance to copulation in the mallard

In the majority of socially monogamous bird species, females solicit or accept copulations from males other than their partner. Females may gain direct benefits from extrapair males, such as greater access to resources, or indirect genetic benefits that will influence the future success of their offspring. However, one group of birds appears to be the exception to this general rule; in the wildfowl (Anseriformes), all extrapair copulations appear to be resisted by females. It has been suggested that resistance behavior may be a strategy to allow females a greater choice of mates, either at the precopulatory level (to promote choice of copulation partner) and/or the postcopulatory level (to promote multiple mating to increase their choice of sperm). This paper examines the function of female resistance behavior in one of the dabbling ducks, the mallard (Anas platyrhynchos). Observations on a marked population of wild mallard and experiments with captive birds found that although females showed a strong preference for particular males that are the first to molt into their breeding plumage, male attractiveness did not influence female responses to pair or extrapair copulation attempts. Female resistance decreased the likelihood that copulation attempts would end in successful insemination. The findings did not support the hypothesis that females resist copulations to promote female choice and the reasons why waterfowl may benefit from avoiding all extrapair copulations are discussed. Copyright 2003.

Male provisioning is negatively correlated with attempted extrapair copulation frequency in the stitchbird (or hihi)

In species with biparental care of offspring and high levels of extrapair parentage, paired males may suffer reduced fitness by investing in offspring that are not their own. In such instances, males are predicted to evolve some form of discrimination between kin and nonkin and vary investment accordingly. One simple form of discrimination is to follow behavioural cues to paternity. We investigated paternal contribution to chick rearing in a socially monogamous population of stitchbirds, Notiomystis cincta, with high levels of extrapair copulation (EPC) and extrapair paternity. The relative contribution of the male to chick provisioning was negatively correlated with attempted EPC frequency. Because the majority of EPC attempts are forced and conspicuous in stitchbirds they are an obvious cue for males to use.

Extra-pair paternity in waved albatrosses.

We estimated the rate of extra-pair fertilizations (EPFs) in waved albatrosses (Phoebastria irrorata) on Isla Española, Galápagos, Ecuador, using multilocus minisatellite DNA fingerprinting. Waved albatrosses are socially monogamous, long-lived seabirds whose main population is on Española. Aggressive extra-pair copulation (EPC) attempts have been observed in the breeding colony during the days preceding egg-laying. Our genetic analyses of 16 families (single chicks and their attending parents) revealed evidence of EPFs in four families. In all cases males were the excluded parent. These data suggest that waved albatrosses have an unusually high rate of EPF relative to taxa with similar life histories. Future behavioural observations will determine the extent to which forced vs. unforced EPCs contribute to this high EPF rate.

Strategic allocation of ejaculates by male Adélie penguins.

Sperm competition theory suggests that males should strategically allocate sperm to those females that will bring them the best possible genetic returns. Although males of a number of species of insects and fishes have been shown to allocate sperm strategically, we provide, to our knowledge, the first evidence that an avian species is also capable of allocating ejaculates. Male Adélie penguins (Pygoscelis adeliae) are more likely to transfer sperm during extra-pair copulations (EPCs) than during pair copulations. We investigated the question of how males allocate ejaculates within the constraints of limited sperm availability and found (i) that males that engaged in EPC attempts ejaculated less often when copulating with their social partner than males that made no EPC attempts, and (ii) that there was no difference between males that were involved in failed EPC attempts and those that were involved in successful EPCs in the proportion of copulations that resulted in sperm transfer. These results indicate that males achieve strategic allocation of sperm within the constraints of limited sperm availability by withholding ejaculates from their social partners.

The Frequency and Function of Aquatic Courtship and Copulation in Least, Crested, Whiskered, and Parakeet Auklets

Least (Aethia pusilla), Crested (A. cristatella), Whiskered (A. pygmaea), and Parakeet Auklets (Cyclorrhynchus psittacula) all engage in aquatic courtship and copulation behavior. We quantified auklet sexual behavior at sea to obtain comparative information related to sexual selection and to evaluate why auklets choose this unusual location for mating. Auklet courtship involved a variety of stereotyped displays. Although similar courtship displays occurred both at the colony on land and at sea, copulation took place only on the sea. Courtship and copulation was frequently disrupted by extrapair males. Extrapair copulation attempts occurred in all species and apparently successful unforced extrapair copulations were observed in Least, Crested, and Whiskered Auklets, suggesting that sperm competition is a feature of their mating systems. Male birds risk water damage to their sperm if they mount their female partners at sea and cause their cloacas to become submerged during insemination. Male auklets, lacking an intromittent organ, achieved cloacal contact without mounting the female so that their cloacas remained unsubmerged. Males positioned themselves behind their partners and rapidly flapped their wings, creating lift to bring their cloacas up against their partner's cloacas, pushing upwards and ensuring insemination occurred away from the sea surface. Possible hypotheses to account for exclusively aquatic copulation include predation and sexual harassment avoidance, and female testing of males, but a definitive explanation for this phenomenon remains elusive.

Copulatory behaviour and paternity in the American kestrel: the adaptive significance of frequent copulations

The adaptive significance of repeated withinpair copulations is not well understood. We analysed the copulatory behaviour of 16 pairs of solitary-nesting American kestrels,Falco sparverius, in southern Quebec (Canada), and the achieved reproductive success (paternity) of 21 kestrel families determined by DNA fingerprinting, in terms of four hypotheses. (1) The paternity assurance hypothesis, which suggests that males copulate frequently to avoid being cuckolded, was rejected because there were few extrapair copulation attempts (<1% of all copulations observed), withinpair copulations were not timed during the fertile period and mate attendance did not increase as the fertile period approached. (2) The immediate material benefits hypothesis, which suggests that females trade copulations for food, was refuted because copulations most often occurred without food transfers, especially outside the fertile period. (3) The female mate guarding of males hypothesis, which suggests that females distract their mates from other mating opportunities by copulating frequently, was rejected because extrapair copulation attempts were infrequent, male and female solicitation frequencies were similar and females did not differ in the timing or frequency of solicitations. (4) The mate assessment hypothesis, which suggests that assessment of mate quality is mediated via copulation, most closely predicted the behaviour observed since withinpair copulations were frequent outside the fertile period and at pair formation, males and females solicited similar numbers of copulations and pairs did not differ significantly in solicitation or copulation frequency. In line with this hypothesis we found that only one brood was extrapair, probably the result of mate replacement.

Extra-pair mating effort of male hooded warblers,Wilsonia citrina

Few researchers have been able to quantify the time or effort expended by male birds in seeking extra-pair copulations with neighbouring females. In this study, we radio-tracked male hooded warblers, to determine the frequency and duration of intrusions onto neighbouring territories. Extra-pair fertilizations are common in hooded warblers, with 35% of females producing extra-pair young. Males intruded onto territories where females were nest building more often than expected by chance and approached females during most intrusions (78%), suggesting that these intrusions were extra-pair copulation attempts. Almost all intrusions (96%) were to adjacent territories, and males made an average±seof 0.4±0.2 forays/h and spent 4.7±2.6% of their time off-territory. Males were involved in fights or chases with the resident male in 21% of intrusions, but were apparently undetected during most intrusions. Males with high intrusion effort onto neighbouring territories had the lowest rate of intrusions onto their own territory by other radio-tracked males. Males varied extensively in their intrusion effort, but this was not significantly correlated with male body mass, age or song rate. The percentage of time spent intruding onto other territories was small (0–8%), so males probably do not face strong trade-offs between making extra-pair copulation forays and other activities like mate guarding and feeding offspring.

Fitness components associated with alternative reproductive tactics in cliff swallows

Two common alternative reproductive tactics are intraspecific brood parasitism and extrapair mating. Understanding the evolution of these traits requires estimation of fitness for individuals that do and do not exhibit diem. We analyze fitness components associated with brood parasitism and extrapair mating in cliff swallows (Petrochetidon pyrrhonota). Annual survival probabilities for females known to be parasites, hosts, and nonparasites/nonhosts differed significantly, with highest survival (0.761) for parasites and lowest (0.289) for host females parasitized by egg laying. Survival probabilities did not differ among males paired to females of different status. First-year survival probabilities in die absence of ectoparasitic swallow bugs (Otdocus vicarius) were 0.546 for young raised in die brood parasites' own nests versus 0.354 for young from all other nests; first-year survival probabilities in die presence of swallow bugs were 0.223 for young raised in host nests versus 0.132 for young from nests not brood parasitized. Males that engaged in extrapair copulation attempts had an annual survival probability of 0.413, signficantly lower than die 0.614 estimated for males that were not seen engaging in extrapair mating. Annual reproductive success, measured as recruitment to breeding age, was greatest for brood parasites and similar among other classes of birds in die absence of swallow bugs and was greater for hosts than for birds not brood parasitized in die presence of swallow bugs, likely because hosts occupied less infested nests. Estimated lifetime reproductive success was highest for parasites and their mates. There were no apparent long-term effects of brood parasitism on survival of adult hosts or offspring from host nests, both because hosts did not have enlarged broods and because clutch and brood size did not affect cliff swallow survival. Brood parasites have greater fitness than hosts and nonparasitized birds, probably because parasites are superior individuals in good condition to start with. That males who participated in extrapair mating had lower expectation of survival suggests that extrapair copulations in cliff swallows are perpetrated by inferior males, and females should probably avoid diem. Key xuords: alternative reproductive tactics, brood parasitism, cliff swallows, coloniality, extrapair copulation, fitness, life history, Petrochelidon pyrrhonota, reproductive success, social behavior, survival. [Behav Ecol 9:158-171 (1998)]

Copulation and mate-guarding patterns in polygynous European starlings

We recorded the timing and frequency of copulation and mate-guarding behaviour during the fertile period in relation to day of first ovulation and time of day in the facultatively polygynous European starling,Sturnus vulgarisAll within-pair copulations were female-solicited. Females solicited them at a high rate during both the pre-ovulatory and ovulatory period, but there were differences in solicitation rates between monogamous, primary and secondary females. Extra-pair copulation attempts were all male-initiated and females rarely engaged in them. Attempts by males were most frequent during the ovulatory period, when the probability of extra-pair fertilization was highest. Males intensively guarded their mate during both the pre-ovulatory and ovulatory period. In contrast to most other passerines, female starlings lay their eggs not at dawn but usually between 0900 and 1100 hours, implying that they may be most fertile in the late morning. During the ovulatory period, extra-pair copulation attempts were more frequent in the late morning than in the early morning, suggesting that males try to take advantage of this putative ‘insemination window’. Accordingly, there was some indication that mate guarding during the ovulatory period was more intense in the late than early morning. Females solicited within-pair copulations at a higher rate in the early morning than in the late morning, but copulation rate did not differ between early and late morning. The proportion of monogamous and polygynous males attempting extra-pair copulations did not differ significantly, but mate-guarding intensity differed significantly between female categories. Primary females were guarded less intensively than monogamous females suggesting that males trade mate guarding against mate attraction/courting additional females.

Male detention affects extra-pair copulation frequency and pair behaviour in western bluebirds

Male western bluebirds,Sialia mexicanashow patterns of mate following consistent with mate guarding. The hypothesis that males prevent extra-pair copulations by guarding their mates was tested using 1-h male detention experiments. Males were caged on territory in view of the female, visually occluded on territory or removed from the territory altogether (visually+vocally occluded). Extra-pair males were more likely to join females within 15m and attempt to copulate with them in the three detention treatments than in treatments where males were captured and released or not manipulated at all. Detention also increased the number of females accepting one or more extra-pair copulations. The increased frequency of extra-pair copulations was not caused by movement of females away from their nests, nor by increased rates of vocalization by resident males or females. Extra-pair events occurred shortly after the resident male was caught, suggesting that extra-pair copulations can occur during brief lapses in mate following. Intruding males were usually neighbours with mates and nests of their own. Half intruded when their own mates were at peak receptivity, suggesting that males leave their own fertile mates to seek extra-pair copulations. Detained males did not compensate for detention by increasing the frequency with which they copulated with their mates after they were returned to the territory. Acceptance of extra-pair copulations by females did not increase with the number of extra-pair copulation attempts and females were no more likely to participate in extra-pair copulations when resident males were visually occluded than when they were visually present. Only half of the females that experienced extra-pair copulation attempts accepted one or more extra-pair copulations. Although male detention resulted in an increase in the frequency of extra-pair copulations in western bluebirds, females appeared to be selective about participating in extra-pair matings.

Mate Switching and Copulation Behaviour in the Adélie Penguin

[In monogamous species of birds sperm competition may result from either extra-pair copulations or mate switching. Copulation behaviour in individuals involved in extra-pair activity is well documented while little attention has been paid to mate switching. The aim of this study was to examine copulation behaviour in the Adelie penguin (Pygoscelis adeliae), a species in which females copulate sequentially with more than one male. 14.9% of females switched mates during the pre-laying period; all of these females engaged in successful copulations with both initial and final males. An estimated 9.8% of females engaged in successful EPCs over the same time period. Females that switched mates had on average 8 successful copulations with their initial partner while females that engaged in extra-pair copulation attempts had on average only 0.5 successful copulations with their extra-pair partner. These same females had on average 17 pair copulations per clutch. So in both cases females had significantly more copulations with their final, pair male than their initial partner or extra-pair partner. Frequencies of copulation that are higher than necessary for fertilisation are consistent with mechanisms of both last male sperm precedence and proportional representation. However there is no support for last male sperm precedence from either diurnal or seasonal patterns of copulation relative to fertilisation. It appears that a high frequency of copulation may have evolved in pair males to protect paternity against initial males in this species., In monogamous species of birds sperm competition may result from either extra-pair copulations or mate switching. Copulation behaviour in individuals involved in extra-pair activity is well documented while little attention has been paid to mate switching. The aim of this study was to examine copulation behaviour in the Adelie penguin (Pygoscelis adeliae), a species in which females copulate sequentially with more than one male. 14.9% of females switched mates during the pre-laying period; all of these females engaged in successful copulations with both initial and final males. An estimated 9.8% of females engaged in successful EPCs over the same time period. Females that switched mates had on average 8 successful copulations with their initial partner while females that engaged in extra-pair copulation attempts had on average only 0.5 successful copulations with their extra-pair partner. These same females had on average 17 pair copulations per clutch. So in both cases females had significantly more copulations with their final, pair male than their initial partner or extra-pair partner. Frequencies of copulation that are higher than necessary for fertilisation are consistent with mechanisms of both last male sperm precedence and proportional representation. However there is no support for last male sperm precedence from either diurnal or seasonal patterns of copulation relative to fertilisation. It appears that a high frequency of copulation may have evolved in pair males to protect paternity against initial males in this species.]

Forced extra-pair copulation and mate guarding in the white-cheeked pintail: timing and trade-offs in an asynchronously breeding duck

Abstract. Males employing a mixed reproductive strategy may increase their fitness through extra-pair copulations (EPCs), but also risk lost paternity when they leave their own mate unguarded. How males maximize the effectiveness of forced extra-pair copulation (FEPC) attempts while minimizing the risk of cuckoldry was studied in a non-migratory population of the white-cheeked pintail, Anas bahamensis bahamensis, a tropical species with extended breeding seasons. Despite substantial asynchrony in the laying dates of females, males directed FEPC attempts primarily at females in fertile condition. The rate of pair copulations also peaked during the female's fertile period, but 23.1% of all successful copulations with laying females were FEPCs. Males guarded their paternity by vigorously defending their mates from males attempting FEPC, by escorting females to their nests, by defending a territory, and by forcing copulation on their own mates after they had been subjected to an FEPC attempt by another male. Contrary to expectation, males did not temporally partition mate guarding and FEPC activity but pursued FEPCs primarily during the period when their own mates were fertile. There was no evidence, however, of a trade-off between FEPC activity and the quality of male mate guarding. Females paired to males with the highest FEPC rates were rarely subjected to FEPCs themselves. In addition, although females that abandoned nesting efforts suffered a high frequency of FEPC attempts, their mates were much less active in FEPCs than the mates of females that nested successfully. These results suggest substantial variation in male quality: some males excelled at both guarding their mates and achieving FEPCs, while others neither pursued FEPCs nor mate-guarded effectively.