Size-assortative nest choice in the absence of competition in males of the sand goby,Pomatoschistus minutus

Synopsis Size-assortative choice of nest site is commonly found among fish with paternal care. This pattern can be explained either by the superior competitive ability of large males for preferred large nests, or by a choice of nest size that is related to the male's own body size. Choice of nest size was studied in males of a small marine fish, the sand goby Pomatoschistus minutus, by providing artificial nest sites in laboratory and field experiments. A positive correlation between nest size and male size, indicating a size-assortative nest choice process, was found in both aquarium and field experiments. This is argued to be the outcome of a preference for an optimal nest size and not to be due to competition, as (a) a surplus of nest sites was available to the individuals in nature; (b) in the aquarium experiments, single males of all sizes, when offered a choice between a smaller and a larger nest site, showed a preference for nests in proportion to their body size and not for the largest available nests; and (c) in the aquaria, when single males were offered only a small or only a large nest site, small males abstained from building nests in the large sites, whereas in the small nest sites males of all sizes built nests. My conclusion is that size assortative nest choice occurred in the absence of competition, which thus is not a necessary condition for size-assortative nesting, contrary to what is commonly assumed in many studies. This preference may represent a compromise (or trade-off) between the advantage of a nest large enough to accommodate many eggs and a smaller one with lower maintenance and defence costs.     

Size-assortative nest choice by the Japanese fluvial sculpin in the presence of male-male competition

Nest choice by the Japanese fluvial sculpin Cottus pollux and its relationship to male reproductive success, was examined in a natural habitat, central Japan. The larger males tended to occupy the deeper nest cavities, suggesting size-assortative nest choice by the species. Stepwise regression analysis showed that cavity area was correlated positively to male reproductive success. Nest choice experiments without a competitive male indicated an absence of size-assortative nest choice, but larger males tended to choose a large nest when another male was present, suggesting that size-assortative nest choice by the species is attributable to male-male competition for large nests, such being related to a resource-defence polygynous mating system.     

Male Nest Choice in Sand Gobies, Pomatoschistus minutus

Although material resources can have a direct bearing on the fitness of both sexes, few studies have actually examined resource-based preferences from a male choice perspective. In sand gobies, Pomatoschistus minutus , the size of a male's nest influences his attractiveness to females and also dictates the number of eggs he can receive. Thus, one might expect males to prefer larger nests. However, an earlier study of marine sand gobies from a population with a surplus of nest sites and high nest predation found that males exhibited size-assortative nest preferences. Here, we investigated male nest preferences from a brackish population characterised by a chronic nest shortage but lower predation risk. A survey of naturally settled nests in the field (shells and rocks) showed a pattern of size-assortative nest occupancy consistent with the previously studied population, with larger males occupying larger (i.e. rock) nests. However, when offered a choice of potential nests in the absence of male competition, we found that all male gobies in our population, irrespective of their own body size, actually preferred larger nests. Moreover, a predilection towards large nests superseded any preferences based on nest colour. Our results not only indicate the existence of male preferences for material resources but, considered in the light of previous work, also suggest that such preferences may vary among populations and, importantly, may not necessarily be realised in a competitive setting.     

Big is better: the importance of size for reproductive success in male Pomatoschistus minutus (Pallas) (Pisces, Gobiidae)

The sand goby, Pomatoschistus minutus , was used in aquarium experiments to study the importance of body size for the ability of males to gain access to nest sites and mates. When several male and female P. minutus were allowed to reproduce together, on average, half of the males built nests, and half of those males obtained eggs in their nests. Males with nests were significantly larger than males without nests, and nests with eggs belonged to males larger than the males with empty nests. In another experiment, when two males were competing for one nest, the largest male occupied the nest when both fish were put into the aquarium simultaneously. However, when the smaller male had been allowed to establish a nest before the larger male was introduced, the small male could usually retain the nest. Males with a body length < 50 mm did not build nests at all in the early part of the breeding season. In female choice experiments, no preference for larger males was found. Thus, male-male competition for nest sites and behavioural differences between different sized males seem to be the main factors influencing the non-random mating success in male P. minutus.     

Threat-sensitive Nest Preferences in Male Upland Bullies,Gobiomorphus breviceps

A male's ability to acquire and defend a nest site against competitors is an important requirement for successful breeding in many fish species. In the upland bully Gobiomorphus breviceps (Eleotridae), not all males are successful in gaining ownership of nesting rocks; therefore, male-male competition may be important in nest acquisition. Although larger nests have the potential to hold more eggs, in nature there is a preferred nest size well below the maximum available. I found that in over 88% of dyadic contests, the larger male was successful in acquiring the single nesting site provided. When males were individually given a choice of two artificial nest rocks, they consistently preferred the larger nest. These results suggest that larger males have the ability to occupy the largest nests. In the presence of a trout predator, males preferred nests with three closed sides 93% of the time. This preference disappeared when the threat was a conspecific. This shows that while males were choosing the larger nests their decisions were also threat-sensitive.     

Female choice and male competition in longear sunfish

Mating systems with spatial clumping of nests or display sitestheoretically can result from female preference for clumpedmales or from competitive interactions among males. We testedpredictions derived from these two types of models against observationsof nest dispersion, mating success, and alternative male matingtactics in a naturally occurring population of central longearsunfish (Lepomis megalotis megalotis). The data were consistentwith models for male-initiated spatial clumping of nest sites;no evidence of female preference for clumped nests was found.We observed that large males had greater mating success thansmall males and that solitarily nesting males were larger thancolonial males; the most successful males were solitary nesters.Mating success of large males did not increase with colony size.Furthermore, colonial males were often cuckolded by neighbors,whereas solitary males were not cuckolded. We propose that colonialnesting is maintained in longear sunfish because group nestingallows subordinate males to obtain access to females.     

Tactic changes in dusky frillgoby Bathygobius fuscus sneaker males: effects of body size and nest availability

Field and laboratory studies were conducted to examine the effects of nest availability and body size on changes in male mating tactics from sneaking to nest‐holding in the dusky frillgoby Bathygobius fuscus. In the field, the body size of nest‐holding males decreased from early to mid‐breeding season, suggesting the possibility of a change in the tactics of sneaker males to nest‐holding. Many sneaker males did not use vacant spawning nests even when size‐matched nests were available, but they continued to reproduce as sneakers. Similarly, in aquarium experiments with available vacant nests, some sneaker males became nest‐holders irrespective of their body size, but some did not. These results showed that nest availability is not a limiting factor for changes in tactics by sneaker males in this species. Because tactic‐unchanged sneaker males were co‐housed with larger nest‐holding males in the tanks, the body size of nearby nest‐holding males may have affected the decision to change tactics for sneaker males. Moreover, smaller individuals among tactic‐changed males tended to spend more time until spawning, probably because they had relatively larger costs and smaller benefits of reproduction as nest‐holding males compared to larger males.     

Effects of resource holding potential and resource value on tenure at nest sites in sand gobies

Over a broad range of animal systems, male reproductive successdepends on resource holding potential (RHP) and resource quality.In a field study, we randomly combined males of different sizeswith nests of different sizes to investigate the relative roleof resource holding potential and resource quality in determininga sand goby, Pomatoschistus minutus, male's nest tenure. Individuallymarked small and large males were given either small or largeflowerpots for nests in isolation and were exposed to intrudersafter they had built nests. We found that nest tenure was longerfor big males and owners of big nests. In most cases (34 of51) the original nest owner was replaced by a bigger male. Thesereplacements by larger males were probably due to takeoversby stronger intruders. Replacement males were larger at bignests. Our results support resource defense theory, as individualswith higher RHP and more valuable resources defended their nestfor longer. On nine occasions males abandoned their nests. Ownersof these nests were larger than the nest owners that were replaced.Hence, our results may provide an example of a situation inwhich sand goby males are able to judge the reproductive valueof their current situation and act accordingly.     

Male and female preferences for nest characteristics under paternal care

Nests play a critical role for offspring development across the animal kingdom. Nest quality may contribute to the builder's extended phenotype and serve as an ornament during mate choice. We examined male and female nest choice in the common goby (Pomatoschistus microps), a benthic fish with male‐only parental care where females deposit eggs in male‐built nests. Using prebuilt nest models, we independently manipulated two candidate nest quality traits: (a) nest entrance width with a role in oxygen ventilation, and (b) extent of sand cover with a role in camouflage. In simultaneous choice trials, male gobies exhibited no preference for any nest model type. This suggests that initial characteristics of a nesting substrate have minor importance for males, which usually remodel the nest. Females were given a choice between two males occupying either entrance‐ or cover‐manipulated nests. The same pair of males was then exposed to a second female but now with alternated nest types assigned. Most females were consistent in choosing the same, typically the heavier male of the two regardless of nest properties. However, the females that chose the same nest regardless of the male preferred low over high sand coverage and narrow over wide nest entrance. Our results indicate that females base their mating decision on a combination of male phenotype and nest traits. While we found no indication that females are attracted to highly decorated nests, our study is the first in fishes to disentangle a preference for narrow (and thus more protective) nest entrances independent of nest coverage.     

Female mate choice,male-male competition and parental care in the river bullhead,Cottus gobio L. (Pisces,Cottidae)

Male body size was tested for its influence on female mate choice, male-male competition and ability to defend broods in the river bullhead, Cottus gobio L., a polygynous fish with paternal care. Females presented with two potential mates of different sizes significantly preferred to spawn with the larger male. Males smaller than, or 1·5 times longer than, the female were rarely selected as mates. Larger males were more successful in defending their brood from conspecifics, which may explain female preference for them. Unmated large males displaced smaller guarding males from their nests and retained the acquired egg masses. Competition between males for nest sites with eggs can be accounted for by the preference of females for males already guarding eggs: by seizing a nest containing egg masses, a male will increase his chance of being chosen.     

Male–male competition for large nests as a determinant of male mating success in a Japanese stream goby, Rhinogobius sp. DA

Males of the stream goby Rhinogobius sp. DA (dark type) court females in deep pools and care for the eggs under stones in shallow riffles. We studied male–male competition for access to females and nest sites to understand how male size influences the mating success of this species. In field observations, larger males won in fighting with other males. However, large males did not tend to monopolize courtship opportunities, and the frequency of successful courtships, after which males led the females to the nests, was not related to male body size. The fact that courted females always escaped from the fighting sites once males began fighting likely explains why male size was not positively related to courtship success. Large males occupied large nest stones, and the number of eggs received in the nest was correlated positively with nest size. In aquarium experiments with two tiles of different sizes provided as nesting materials, males always chose the larger nest and, when two males were introduced simultaneously, the larger one occupied the larger nest. These results suggested that male mating success of this goby is determined by male–male competition for large nests rather than for access to females. Received: June 9, 2000 / Revised: September 2, 2000 / Accepted: October 4, 2000     

Rapid assessment of female preference for male size predicts subsequent choice of spawning partner in a socially monogamous cichlid fish

Although size-assortative mating in convict cichlids, Amatitliana nigrofasciata, is supposed to result from mutual mating preference for larger individuals, female choice in relation to male size remains ambiguous. We revisited the evidence for directional preference for larger males in female convict cichlids using a classical two-way choice apparatus in which each female could decide to spend time in front of a small male or a large one. We found evidence for female preference for large males, as assessed from association preference during a 4-hour period following encounter. Furthermore, females decided to spawn in front of the initially preferred male more often than expected by chance. Our results thus confirm the existence of a directional preference for large males in female convict cichlids, and indicate that association preference measured over a short period of time can provide a quick and reliable proxy for reproductive preference in this species.     

Social status-dependent nest choice of territorial males under reproductive parasitism in a Lake Tanganyika cichlid Telmatochromis vittatus

Field and laboratory studies were conducted to examine how territorial males of a Lake Tanganyika cichlid Telmatochromis vittatus balance the conflicting demands on nest choice between occupying large nests with more females and avoiding reproductive parasitism (nest piracy, which is adopted by the largest males in the population). Pirates less frequently intruded the nests farther from neighbours, perhaps due to the costs associated with travelling between nests. The field experiment showed that territorial male T. vittatus sacrificed the fitness benefits that large nests offer and instead prioritized occupying the nests farther from neighbours on which fewer pirates intruded. The field observations suggested that they adopt different strategies for nest choice according to their relative competitive ability to pirates; the large territorial males, who are size-matched to pirates and can defend their nests against them, compete for larger nests among the more-isolated nests, whereas subordinate territorial males, which are smaller than pirates and thus inferior to them, compete for the more-isolated nests among the less-isolated nests. These findings suggest that the territorial male T. vittatus chooses the more-isolated nests to avoid pirate males at the expense of occupying large nests.     

Provisioning behaviour at the nest in single-parent versus biparental nests and male versus female parents in the common redstart (<Emphasis Type="Italic">Phoenicurus phoenicurus</Emphasis>)

We analysed video-sequences of undisturbed parental provisioning behaviour on 12 nests of common redstart (Phoenicurus phoenicurus). In 4 of the 12 nests, chicks were fed by a single parent only. We compared provisioning rate of chicks, time spent on the nest and food allocation rules between nests with uniparental and biparental care and between male and female parents in biparental nests. In nests with a single parent, the frequency of feeding visits per parent was higher than in biparental nests. As a result, the rate of food provisioning of chicks was similar in uniparental and biparental nests. The food allocation rules did not differ between uniparental and biparental nests. In biparental nests, male and female provisioning behaviour was similar though with two exceptions: males had a strong preference for feeding chicks in front positions in the nest and females spent a longer time on the nest after feeding. We conclude that single common redstart parents are able to compensate fully for the absence of the other parent through increased provisioning efforts, and that in biparental nests, males and females contribute equally to the provisioning of the young.     

Maternal investment in a bee species with facultative nest guarding and males heavier than females

1. Maternal investment can be influenced by several factors, especially maternal quality and possibilities for future reproduction. Mass provisioning Hymenoptera are an excellent group for measuring maternal investment because mothers distribute food sources to each brood cell for each offspring separately. Generally in aculeate Hymenoptera, larger females produce larger offspring and invest more in female offspring than in male offspring. 2. This study investigated patterns of maternal investment in Ceratina chalcites, which has an uncommon type of sexual size dimorphism in Hymenoptera: on average, males are heavier than females. It was found that larger females produce a significantly higher proportion of male offspring, as males are the costlier sex in this species. 3. Facultative nest guarding by females was observed. Females can guard offspring until adulthood, as is typical for bees of genus Ceratina (34.43% of nests); however, in the majority of cases (65.56% of nests), females plug and abandon the nest. Significant differences were found in the amount of investment between guarded and unguarded nests. Guarded nests had a greater number of provisioned brood cells and a higher proportion of male offspring. It is suggested that mothers have two facultative strategies – either she makes a large investment in the offspring of one nest or she abandons the first nest and carries out a second nesting elsewhere.     

Elaborate Nests in a Weaverbird: A Role for Female Choice?

Studies on sexual selection have focused on behaviour and morphology, but several groups of animals build elaborate structures associated with acquiring a mate. I investigated female choice for nests built by male baya weavers (Ploceus philippinus). Nest choice by females should be strong, as nests are obvious direct benefits provided by males. I used a field experiment supplemented with correlational information to ask whether females appear to base mate choice decisions on male behaviour, nest architecture, and nest location. When the nests of highly visited males were exchanged with those of poorly visited males, female visits remained highest at the original male and location. I found no relationship between female choice and male display or other behaviour. Correlational analyses show that nest location was a better predictor of female choice than was nest architecture. These data suggest that current female choice is driven more by access to safe nesting sites rather than to well‐built nests, possibly because all males are able to build nests of adequate quality. However, nest architecture is unlikely to be irrelevant to females, and its role deserves further investigation.     

Reproductive success in male sunbleak, a recent invasive fish species in the U.K.

The spawning behaviour of male nest guarding sunbleak Leucaspius delineatus , a recent invasive species in southern England, was studied and quantified for the first time. In the absence of physical differences between territorial and non‐territorial males ( i.e . colour, size, etc .), the reproductive behaviour of territorial males was analysed and related to reproductive success. The results showed that females preferred high‐courting and highly aggressive males. The initial cue in female mate choice, however, was based on courtship, while aggression was the decisive behavioural trait in influencing mate choice, providing a direct signal of physical condition and 'paternal competence'. Some males picked nest sites which were subsequently preferred by other males taking over the nest of a previous male ('communal nest'), with the new territorial male adopting the eggs already present at the nest. It appears that either due to female preference for nests already containing eggs or lower rates of sired egg predation by dilution among unrelated eggs, sunbleak males have adopted the mating strategy of allopaternal care.     

Sequential settlement by nesting male and female Baya weaverbirds Ploceus philippinus: the role of monsoon winds

Theory predicts that females should track resources while making decisions about where to reproduce, and males should track females. However, when males create the resource that females require, female settlement follows that of males. In this situation, how do individuals make settling decisions and what are the fitness consequences of these decisions? Here, I test the hypothesis that environmental factors (wind direction and velocity) affect optimal nest placement and orientation, and thus male and female settlement, in Baya weaver Ploceus philippinus colonies. Nests experimentally placed in windward locations with entrance tubes oriented toward the wind were more likely to lose clutches of artificial eggs than were nests placed in other combinations of placement and orientation. Correspondingly, males built their nests strongly clustered on the leeward side of colony trees, with entrance tubes oriented away from the wind. However, females did not discriminate amongst natural nests on the basis of nest placement or orientation. This may be because the effect of wind on the success of natural nests was small and was overwhelmed by other causes of nest loss. I suggest that, in some situations, female preference may remain undetected because the options available to females are constrained by preceding settlement decisions by males. In these cases, it is necessary to manipulate male distribution outside the range of natural variation to gain a better understanding of selective pressures imposed by female preferences.     

Nest Green Plants as a Male Status Signal and Courtship Display in the Spotless Starling

The use of green nest plants by birds has received much attention in recent years. Although many hypotheses have been put forward to explain the functional significance of this trait, three of them, the courtship hypothesis, the nest protection hypothesis and the drug hypothesis, have particularly captured the interest of researchers. In this paper we demonstrate that in the spotless starling, Sturnus unicolor (1) most of the green plants were carried to nests during the 10 d that preceded the start of egg laying, (2) males that controlled a greater number of nest boxes, so that they mated with more females, also carried a larger amount of green material to each of their nests, (3) males carried larger amounts of green plants in second than in first clutches, and (4) monogamous males did not exhibit this last tendency when they mated with inexperienced females. Thus, plants seem to exert a function during the female fertile period but not during incubation or nestling stages. The amount of green plants added by a male may be seen as a honest signal of attractiveness and status. We suggest that males uses green plants to stimulate females to breed in it so that they carry more plants in second clutches, when females might be more reluctant to breed. This strategy was apparently constrained in monogamous males mated with inexperienced females probably because parental duties, rarely recorded in polygynous males, limits the time available to carry plants to nests. We also discuss to what extent other hypotheses may further explain the evolution of green plants carrying in starlings.     

Mixed species nesting associations in Darwin's tree finches: nesting pattern predicts predation outcome

Predation is the main cause of passerine nesting failure. Traditionally, large intraspecific group size is thought to accrue individuals with fitness benefits from increased predator vigilance and hence lower predation risk. To date, few studies have investigated interspecific group size in relation to predation risk. In the present study, we examined predation outcome in Darwin's small tree finch, Camarhynchus parvulus , in nests with many or few interspecific neighbours. We tested the predictions: (1) nests in mixed associations have lower predation than do more solitary nests; (2) mixed species nesting associations covary with nest site vegetation characteristics; (3) older (i.e. presumably experienced) males more commonly nest in mixed associations than younger males; (4) older males select more concealed nesting sites; and (5) controlling male age, females prefer to pair with males in mixed associations than at solitary nests. Almost half of all nests occurred in mixed associations (46%) compared to solitary nests (54%), and the overall distribution of nests was decidedly nonrandom, displaying a bimodal pattern. Nest site vegetation characteristics of the focal species were inconsistently associated with nesting pattern, but older males did select more concealed nesting sites. Controlling differences in surrounding vegetation characteristics, mixed nesting associations experienced markedly lower predation than solitary nests, and females showed a preference for males in mixed associations, as demonstrated by higher male pairing success.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 313–324.