Reproductive success in male Japanese minnows,Pseudorasbora parva: observations under experimental conditions

To evaluate the spawning success of male Japanese minnows,Pseudorasbora parva, and female mate choice, spawning behaviour was observed under both artificial and experimental conditions. Larger males had larger territories and greater reproductive success. The body weight of territorial males decreased during the maintenance of territories, while that of non-territorial males increased significantly. When the weight of non-territorial males exceeded that of territorial males, the former began to establish new territories on the substrate, suggesting a conditional strategy by non-territorial males to trade off immediate reproductive success with growth and hence improve future reproductive success. Females chose males with larger body size, probably based on dominance rank rather than the quality (or size) of territory. It was concluded that females choose males of higher dominance rank and that males compete for large territories, both of which play an important part in male reproductive success.     

Nestbox provisioning in a rural population of Eurasian Kestrels: breeding performance,nest predation and parasitism

The breeding biology of the Eurasian Kestrel Falco tinnunculusin nestboxes in farmland was studied to test for differences between artificial and natural sites. We report on the direct effect of nestbox provisioning on some life-history traits and how nestbox use affects nest predation and parasitism. Five types of nest-sites were available: nestboxes on poles and trees (artificial sites), stick nests on trees, stick nests on pylons and holes in buildings (‘natural’ sites). The Kestrel population increased from 23 pairs in 1993 (prior to nestbox installation) to 55 in 1998 as nestboxes were provided. In general, pairs breeding in trees started to lay later than those nesting in nestboxes on poles or in building holes, but this difference was probably associated with habitat quality rather than nest type. Differences in clutch size were found between nest-sites in some years, and were associated with laying date and, probably, with variation in territory quality. Using only data from successful nests, pairs breeding in nestboxes produce more fledglings than those in building holes or pylons. The frequency of nest predation was higher in natural sites than in nestboxes. The number of fledglings from pairs breeding in nestboxes was higher than from those breeding in old stick nests in trees when all nests were considered. Nestbox provisioning had no effect on the occurrence of the ectoparasite Carnus hemapterus, but chicks from nestboxes showed higher intensity of infection. Our results suggest that nestbox provisioning increases reproductive success and the frequency of nest predation or intensity of parasite infestation in Kestrels.     

Breeding site fidelity in willow ptarmigan: the influence of previous reproductive success and familiarity with partner and territory

Summary Breeding site fidelity is high in willow ptarmigan: only 9% of males and 31% of females switched territories between years. Unpaired males were more likely to switch territories than paired males. For paired males, survival of their previous partner and reproductive success in year x did not influence probability of switching in year x+1. A female was more likely to switch territories if her previous partner disappeared. If her partner returned, she had a higher probability of switching if she did not produce chicks the previous year. Most hens moved to the territories of older males, although hens paired with unfamiliar older males did not have higher reproductive success than those paired with yearlings. Individuals that paired with their previous partner laid earlier and produced heavier chicks than those paired with unfamiliar partners. Excluding birds paired with familiar partners, survival and reproductive success in year x+1 was similar for males and females that did or did not switch territories. Males had a higher probability of producing chicks after switching than before, but females were more likely to lose their clutch after switching. For both sexes, birds that switched territories were as successful as the birds that replaced them on their former territories. We conclude that high site fidelity in willow ptarmigan is maintained because of the benefits of pairing with a familiar partner.     

Caribbean damselfish with varying territory quality: correlated behaviors but not a syndrome

The behavioral syndrome hypothesis suggests that individualanimals within a population behave differently due to specificbehavioral types, and these should be consistent across behaviorsor in different contexts. In contrast, for animals that livewithin an environment in which territory quality can changeover time, natural selection should have favored behavioralflexibility and modulation of the cost of defense in relationto territory quality. This would require assessment of the territoryfollowed by displays of appropriate types and intensities ofbehavior. We examined the territorial behavior of male beaugregorydamselfish (Stegastes leucostictus) by enhancing territory qualityusing artificial breeding sites and comparing their behaviorto males on lower quality natural sites. When male fish weredefending high-quality artificial territories, they had higherlevels of aggression toward male conspecifics and courtshiptoward females than when on low-quality natural territories.We also found that aggression and courtship behaviors were correlatedon natural sites but not on artificial sites. Behaviors werenot correlated within individuals when males switched from naturalto artificial territories or from artificial to natural territories.These results indicate that males assess their current territoriesand adjust behaviors accordingly and that courtship and aggressivebehaviors are not linked within a permanent behavioral syndrome.     

Short-term cues used by foraging trout in a California stream

Stream salmonids choose foraging locations to maximize the energy benefit of foraging within the constraints of size-mediated dominance hierarchies and predation risk. But, because stream habitats are temporally variable, fish must use a search process to monitor changing habitat conditions as a means of locating potentially-better foraging locations. I explored the cues used by the cutthroat trout, Oncorhynchus clarki clarki, when searching for food at the pool scale by artificially increasing prey availability at different locations by using special feeders and by manipulating pool velocities. Behavior of individually marked fish was monitored from stream bank platforms under unmanipulated control conditions and under seven experimental sets of conditions involving different combinations of feeder location and velocity manipulation. Under natural conditions fish elected to forage in the deepest (>50 cm), fastest (0.10–0.25 m s⁻¹) locations and within 1 m of structure cover, but would readily move to shallower (<30 cm) water away from cover if velocities were manipulated to be highest there. Although fish did not locate feeders unless they were placed in high-velocity areas, when high velocity was provided fish would move into very shallow water (<20 cm) if prey were delivered there. Responses of individual trout to manipulations indicated that water velocity was the main physical cue used by fish to decide where to forage, and that fish could also learn about new food sources by observing conspecifics. Overall, results indicated fish were not “perfect searchers” that could quickly locate new food resources over short time scales, even when the new resources were within a few meters of the fish’s normal foraging location. When given the correct cues, however, fish could detect new food sources and defend them against subordinate fish. Movement of new fish into and out of the study pools during the ten-day observation period was common, consistent with the idea that trout used movement as a means of exploring and learning about habitat conditions at the reach scale.     

Nest‐site fidelity in parental male bluegill Lepomis macrochirus: spatial patterns and the influence of prior mating success

A 4 year mark–recapture study examined the pattern of nesting site fidelity of parental‐type male bluegill Lepomis macrochirus. The study results indicated that iteroparous male L. macrochirus choose new nest sites near their own previously used sites. The scale of site fidelity varied, but generally males choose to renest within shoreline areas rather than specific or exact nest locations (94% within‐year, 86% among‐years). Iteroparous males also displayed no preference to nest in proximity to neighbouring males from previous colonies to suggest social fidelity. Contrary to expectation, manipulating males' reproductive success had no significant effect on the pattern or scale of male reproductive site fidelity.     

Foraging time allocation in relation to sex by the gulf coast fiddler crab (Uca panacea)

Summary Schoener (1971) proposed that the reproductive demands of animals should be important in shaping their foraging behavior because fitness is affected. He defined two forager types: energy maximizers (reproductive success depends on energetic intake) and time minimizers (reproductive success depends on time spent in activities other than foraging), and suggested that females most often illustrate the former and males the latter. We tested whether mating activities influence the foraging behavior of Uca panacea, and the predictions that females would be energy maximizers because of their reproductive strategy and that males would also be energy maximizers because of their courtship activity. Time allocated to foraging by 800 male and female fiddler crabs (at two sites) was quantified; no significant difference in foraging time was found between the sexes. Both male and female crabs allotted a large portion of their time to foraging because both sexes depend on stored energy during their reproductive bouts. Our results show that the particular forager type can be predicted based on reproductive demands, but a forager type can not always be assigned to a particular sex without consideration of all important ecological and physiological factors determining reproductive success.     

Large males have a mating advantage in a species of darter with smaller, allopaternal males Etheostoma olmstedi

Theory suggests that males that are larger than their competitors may have increased mating success, due to both greater competitive ability and increased attractiveness to females. We examined how male mating success varies with male size in the tessellated darter Etheostoma olmstedi. Previous work has shown that large males tend to move around and breed in vacant breeding sites, and consequently provide less care for their eggs, while smaller individuals can be allopaternal, caring for the eggs of other males as well as for their own. We studied female egg deposition in a natural breeding population using artificial breeding sites and in the laboratory, where female choice of spawning site was restricted to two breeding sites tended by two males of different sizes. In both the field and the laboratory, nests tended by larger males were more likely to receive new eggs. Additionally, the mean size of males associated with a nest was positively correlated with both the maximum coverage of eggs at the nest and the number of times new eggs were deposited. We discuss how the increased mating success of larger males, despite their decreased parental care, may help explain allopaternal care in this species [Current Zoology 56 (1): 1-5, 2010].     

Communication breakdown? Habitat influences on black-capped chickadee dawn choruses

The dawn chorus of the black-capped chickadee (Poecile atricapillus) is a communication network that functions in the dissemination of essential information for both males and females. Habitat type may influence the performance of this network, and if recognized, chickadees may attempt to behaviorally compensate for detrimental changes in the form of increased movement. We studied the dawn chorus of 66 black-capped chickadees in two adjacent, yet structurally different, habitats (disturbed and undisturbed) during the summers of 2000–2003 and recorded via point counts the number of neighboring males heard singing simultaneously while following a focal chorusing male and observing his movement. A transmission study to detect differential degradation due to habitat type was also conducted within the same research site. Observers in the disturbed sites heard significantly fewer neighboring males in the focal male's territory than in the undisturbed site, yet individual movement did not differ between habitat types. Propagation of song of varying frequencies, as measured by entropy, suffered less degradation in the disturbed site for high-frequency songs, but there was no effect of habitat on low- or mid-frequency songs. Greater interneighbor distance in the disturbed site likely explains some of the reduction in audibility of neighboring males during the dawn chorus, but the reduced condition of birds in the disturbed site (implicated from other studies) may also be a factor in explaining the difference in networks. The findings of this study suggest that chickadees in the disturbed habitat are experiencing a compromised communication network, which could impact breeding and other social behaviors.     

The effects of supplemental food on reproduction in parental male smallmouth bass

Synopsis We provided supplemental food for parental male smallmouth bass,Micropterus dolomieu, to determine if food supply limits the reproductive performance of nesting males as measured by care duration, reproductive success and survival of adult males. Although supplementing the diet of parental males had a positive effect on all three reproductive measures, the experiment generated contrasting results in different years. In the first year, supplemental feeding only improved the survival of fed males versus unfed males. In the second year, supplemental feeding increased care duration and reproductive success of fed males but reduced their survival relative to unfed males. Our supplemental feeding improved current or future measures of reproductive performance, but not both simultaneously. The results appear to demonstrate phenotypic plasticity in the extent to which energy from supplemental feeding can be allocated to present or future reproduction.     

Free housing for declining populations: Optimizing the provision of artificial breeding structures

The improvement of habitat quality and reproductive success through the implementation of artificial breeding structures is one of the most widespread in situ conservation strategies applied to the recovery of declining wildlife populations. Several past studies have monitored the use of artificial breeding structures in the wild, but virtually none of them have investigated which demographic and environmental factors actually determine their effectiveness in facilitating reproductive success. Therefore, the aim of the present study was to identify those factors influencing breeding success in artificial structures. With this purpose we surveyed a declining population of a keystone species of Mediterranean ecosystems, namely the European wild rabbit. In Doñana National Park, we sampled during the course of two years the breeding success of wild rabbits from 47 artificial warrens, experimentally provided under different demographic and environmental conditions. In order to determine the relative importance of such factors, we applied an AIC model selection procedure to alternative biological hypothesis groups, postulating that breeding success in artificial structures would primarily depend on population density, food availability and/or predator limitation. We found that the efficiency of artificial warrens in facilitating rabbit reproductive success can vary, with an increase associated with greater pasture availability. Predator limitation by fencing also positively affected rabbit reproduction, but only in combination with high pasture availability. On their own, fencing treatment and population reinforcements had low and null effectiveness facilitating reproduction, respectively, as well as entailing significant economic and biological costs. The best way to improve breeding success in artificial structures, therefore, was through their strategic placement in potential high-quality habitats, i.e. with suitable pasture availability. We suggest that vegetation management can effectively increase carrying capacity and consequently the target species’ reproductive success, especially in fast breeding species like the European wild rabbit. The provision of artificial breeding structures for conservation purposes may significantly benefit from the elaboration of concurrent experimental studies similar to the present research, which can help establish useful guidelines for optimizing future conservation efforts.     

Causes of variable reproductive performance by Southern Ground‐hornbill Bucorvus leadbeateri and implications for management

Range occupancy of the cooperatively breeding Southern Ground‐Hornbill Bucorvus leadbeateri in South Africa has decreased by 65% in the last three generations and the effective management of the remaining populations is hampered by a lack of fundamental understanding of the factors determining reproductive performance. We examined the influence of social and environmental factors on the species' reproductive success in South Africa using data gathered from 23 groups over eight breeding seasons. Some groups had access to artificial nest‐sites, others did not. High rainfall (> 500 mm) over the breeding season led to a decrease in reproductive success, with groups being most successful in years when rain in the vicinity of the nest ranged from 300 to 500 mm. Groups breeding in natural nests were successful only when the proportion of open woodland surrounding the nest‐site was high. Those that bred in artificial nests, where overall breeding success was more than twice as high as those in natural nests, were less dependent on the availability of open woodland. Large groups (more than three birds) bred more successfully than groups comprising only two to three individuals. Group size, helper effects and rainfall cannot be managed to increase the productivity of Ground‐Hornbills but the fact that the availability of artificial nest‐sites and the amount of open woodland around the nest‐site both contribute positively to breeding performance identifies practical and simple management options for increasing the reproductive output of Southern Ground‐Hornbill populations.     

Hot rocks or no hot rocks: overnight retreat availability and selection by a diurnal lizard

I used radio telemetry to determine the effects of substrate size and composition on overnight retreat site selection by western fence lizards ( Sceloporus occidentalis). In watersheds of northern California (USA), these lizards occupy two habitat types differing in substrate characteristics: rocky cobble bars found in the dry, active channels of rivers and grassy upland meadows. Rocky substrates, found almost exclusively on cobble bars, provided warmer potential retreat sites than all available retreat sites on meadows during the first 5 h of inactivity. Only cobble and sand substrates provided retreats with temperatures within the preferred daily active range (32–36°C) during the inactive period for these lizards (1900–0900 hours). Females on a cobble bar used rocks as retreats on >90% of nights during the breeding season whereas females on a meadow used wood (>70% of nights) and burrows (>25% of nights). In contrast to females, cobble bar males used rocks significantly less frequently (<70%) and slept in the open air significantly more frequently (25% vs. <1%). Cobble bar females further, showed a significant preference for cobbles 15 cm thick, whereas the rocks used by males did not differ significantly in thickness from those measured in randomly placed transects. Rocks 15 cm thick were the warmest retreats commonly available on this habitat type. Thus, thermal microenvironments available to and chosen by gravid female lizards differ considerably between river and non-river habitats.     

Habitat quality as a predictor of spatial variation in blue tit reproductive performance: a multi-plot analysis in a heterogeneous landscape

Vertebrate studies have rarely investigated the influence of spatial variation in habitat richness on both short-term (breeding) and long-term (offspring recruitment) reproductive performance using simultaneously multi-patch, multi-habitat type and multi-year approaches at landscape level. Here we present results of such an approach using the influence of two oak tree (Quercus ilex, Q. humilis) species on reproductive performance in Corsican blue tits (Parus caeruleus ogliastrae) as a model system. We found that blue tits breeding in rich broad-leaved deciduous patches consistently laid eggs earlier in the season, and produced larger clutches and more fledglings of higher quality, than those breeding in poor evergreen patches. Also, parents, especially males, were in better physical condition in the broad-leaved deciduous than in the evergreen patches. Surprisingly, estimates of long-term effects of reproduction, such as recruitment rates of locally born offspring, did not differ between the two habitat types. Our results suggest that short-term breeding performance and phenotypic quality of both chicks and parents do not necessarily provide reliable information about contributions to following generations at a scale larger than that of the local study plot. Differences in reproductive performance between the two oak habitat types could not be attributed to density-dependent effects, differences in levels of nest predation, or differences in age structure of the birds. We suggest that habitats that are optimal for breeding are not necessarily optimal for survival after the breeding season.     

Females prefer mating males in the carmine triplefin,Axoclinus carminalis,a paternal brood-guarder

Synopsis This study investigates the role of male mating status in female choice patterns in the carmine triplefin, Axoclinus carminalis, a tripterygiid fish that exhibits paternal care. The distribution of daily reproductive activity is clumped, with many males receiving no mates and some receiving three or more. Females in this species do not prefer larger males, and characteristics of the oviposition site appear to have minimal effects on male mating success. When a female is removed from a male early in the daily spawning period, that male attracts fewer additional females for the remainder of the spawning period than does a control male. These changes in mating success are temporary, and do not affect mating success on subsequent days. A preference for mating males or males that are guarding eggs could provide asymmetric benefits for males to defend oviposition sites. This preference for males with eggs could be acting alone or with other factors such as high variance in oviposition site quality to favor the evolution of paternal care in fishes.     

Habitat selection by dispersing yellow-headed blackbirds: evidence of prospecting and the use of public information

In migratory birds individuals may prospect for potential breeding sites months before they attempt to breed and should use the cues most predictive of future reproductive success when selecting a breeding site. However, what cues individuals use when prospecting and which cues are used in selecting a breeding site are unknown for most species. I investigated whether yellow-headed blackbirds (Xanthocephalus xanthocephalus) prospect for future breeding sites and whether they select breeding habitats based on food availability, male or female density, or the average number of young produced per female in the previous year. Although it is often assumed that migratory birds prospect for potential breeding sites at the end of the breeding season, I investigated this by recording all visits to sites early and late in the breeding season. I found that males and females who visited sites other than the site at which they bred were more likely to disperse than individuals only observed at the site where they bred, and that males and females were more likely to prospect late in the breeding season. Both food availability and density in year ^x were not predictive of the number of young per female in year ^x+1; however, the number of young produced per female at a site in year ^x was predictive of the number of young per female in year ^x+1. As expected, dispersers used the most informative cue, the number of young per female and moved to sites with a relatively high number of young per female. This study suggests that individuals prospect for potential breeding sites late in the breeding season when they can use information gathered from the reproductive success of other individuals (i.e., public information) to select a breeding site.     

Resource availability, breeding site selection, and reproductive success of red-winged blackbirds

Red-winged blackbirds are polygynous and show strong breeding site preferences, but it is unclear which environmental factors regulate their reproductive success and are ultimately responsible for shaping their patterns of habitat selection and their mating system. We evaluated the effect of variation in insect emergence rates on the reproductive success of male and female redwings nesting on replicate ponds. The number of male and female redwings that settled on a pond varied two- to three-fold among ponds, but was not related to insect emergence rates. Insect emergence rates had a positive effect on the number of nestlings successfully fledged by females, the number of nestlings fledged from male territories, and on the mass of nestlings at fledging. Typha stem density also varied widely among ponds, and was positively related to male and female settling density and mass of nestlings at fledging, but not to the number of nestlings fledged by females or males. We conclude that alternative breeding sites differ in their ability to support redwing reproduction, and that the availability of emerging odonates is an important environmental factor influencing the reproductive success of both male and female red-winged blackbirds. Received: 31 March 1997 / Accepted: 3 July 1997     

Influence of nest-site and individual quality on breeding performance in Merlins Falco columbarius

We examined the effects of nest-site quality and bird quality on breeding performance in male and female Merlins Falco columbarius from a long-term study in Saskatoon, Saskatchewan. In addition, we tested whether nest-site quality was associated with survival, as well as lifetime reproductive success (LRS). For females, nest-site quality had little influence on any of the measures of breeding performance or survival. Even so, when females switched nest-sites, they tended to move to better ones. Hatch date was repeatable for the same females occupying different nest-sites but not for the same sites occupied by different females. Among males, birds surviving past each age category tended to occupy nest-sites of higher quality, and LRS was positively correlated with nest-site quality. The relationship between nest-site quality and LRS was heavily influenced by the poorest nest-sites. When males switched nest-sites, they too tended to move to ones of higher quality. In addition, chick hatch date was repeatable neither for the same males occupying different sites nor for the same sites occupied by different males. As with most other raptors, male Merlins provide most of the food for the pair and their young during the breeding season, and differences in nest-site quality may have affected the effort needed by males to secure food. Female Merlins, however, appear still to have considerable control over the timing of breeding.     

Effects of site fidelity and breeding performance on mate retention in a short‐lived passerine,the tree swallow Thachycineta bicolor

We studied the relationship among re‐mating, site fidelity and breeding performance in the tree swallow Tachycineta bicolor using 16 y of data on reproductive biology in a population breeding in nest boxes near Ithaca, New York. Of 217 pairs for which both members survived the non‐breeding season, 76% mated with a new partner and 24% reunited with their previous mate. Pairs did not increase their breeding success by breeding together for more than one breeding season. Males produced fewer fledglings after breeding with a new partner, but females neither increased nor decreased their success when breeding with a new mate. Females who bred with a new partner were younger than females that reunited with their previous mates, and they were more likely to move to a different nest box. Males that bred with a new mate were of similar age to males that reunited, and they did not move more often. The probability of breeding with a new partner was better predicted by female age than by previous breeding success, suggesting that re‐mating was not strongly affected by past breeding performance. Because younger females change breeding sites more frequently than do older females and females that mated with a new partner were younger than females that reunited with their previous mates, we suggest that the tendency of tree swallows to change partners between years is a by‐product of lower site fidelity of younger females rather than a strategy for increasing breeding success.     

Structure and dynamic of a natterjack toad metapopulation (Bufo calamita)

Summary The migratory and reproductive behaviour ofBufo calamita was studied at four neighbouring breeding sites in the northern Rhineland, Germany, from 1986 to 1991. Radio telemetry and marking systems based on toe-clipping and on microchips were used to follow the tracks of toads and for individual recognition. Emphasis lay on estimates of (1) the exchange of reproductive individuals between neighbouring sites, and (2) the reproductive success at each site. Allozyme electrophoresis served to assess the genetic diversity of local populations. More than 90% of all reproductive males showed a lifelong fidelity to the site of first breeding, whereas females did not prefer certain breeding sites. Due to the female-biased exchange of individuals among neighbouring sites the genetic distance between local populations was generally low but increased with geographical distance. This pattern of spatial relations is consistent with the structure of a metapopulation. Morever, up to three mass immigrations of males per breeding period, replacing previously reproductive individuals, suggested the existence of temporal populations successively reproducing at the same locality. Genetic distances were considerably greater between temporal populations than between local ones, indicating partial reproductive isolation. In fact, an exchange of reproductive individuals between the temporal populations at each site was not detected, but gene flow due to the recruitment of first-breeders originating from offspring other than their own seems probable. Thus, natterjack metapopulations consist of interacting local and temporal populations. The reproductive success differed considerably among the four sites and also between the temporal populations. Three out of four local populations had low reproductive success as well as the latest temporal population. The persistence of these populations depended entirely on the recruitment of juveniles from the only self-sustaining local population. This rescue-effect impeded local extinction. The discussion focuses on the modifications required to fit the classical metapopulation concept to the empirical findings and their consequences for the dynamics of amphibian metapopulations.