A promiscuous mating system in the Blue Bird of Paradise Paradisaea rudolphi

We studied nesting behaviour, spatial dispersion of display areas and home range dynamics in the Blue Bird of Paradise Paradisaea rudolphi. We found that (1) females carried out nesting duties alone; (2) males displayed from solitary and dispersed sites; (3) female home ranges overlapped, and (4) males had access to and displayed to numerous females. These data suggest a promiscuous mating system in the Blue Bird of Paradise and resolve earlier controversy over this issue.     

Communal Nesting among Genetically Similar House Mice

From March to October 1986, 35 house mice, Mus domesticus, were fitted with radio-transmitters and tracked in and around a Colorado feed shed for an average of 5 (range 2 to 17) days. 5 of 36 simultaneously tracked pairs of lactating females used identical nesting sites. Genotypic similarity at 5 enzyme loci, assayed from biopsies of blood and toes, indicated that these females were more genetically alike than would be expected if pairing occurred randomly among females. We posit that female house mice recognize and preferentially form communal nests with close relatives. Aside from the communally nesting females, minimal overlap occurred among home ranges of lactating females. Only 4 of 10 adult male home ranges appreciably overlapped female home ranges. The home ranges of these 4 males overlapped less than the other adult male home ranges suggesting that males defend one or more females for access to mating. The possibility that communally nesting females are nursing each other's pups is discussed.     

Consequences of a female-biased sex-ratio in a socially monogamous bird: female-female pairs in the Roseate Tern Sterna dougallii

In the socially monogamous gulls and terns, female-biased sex ratios are sometimes revealed by the occurrence of ‘supernormal clutches’, which are usually attended by female-female pairs or other multi-female associations. We studied these phenomena in the endangered Roseate Tern Sterna dougallii at Bird Island, USA, from 1970 to 1995. DNA-techniques were used to sex breeding adults in 1992–94. Supernormal clutches (with three or four eggs) have comprised 1–7% of all Roseate Tern clutches at Bird Island since at least 1970, probably increasing in frequency since 1980. Supernormal clutches were spatially clustered; most were laid late in the peak period of nesting during each season. More than 80% of supernormal clutches and at least 7% of normal clutches were attended by multi-female associations; most of these were female-female pairs, with a few trios (male + two females, or three females) and one quartet (four females). More than half of the multi-female associations attended normal clutches. Some female-female pairs were maintained for up to five years. The age-distribution of females mated to females did not differ significantly from that of females mated to males. Females mated together usually laid eggs synchronously (±2 days). Such females laid fewer eggs than females mated to males (means 1.20 versus 1.73), and had lower fertility and hatching success (about 46% versus 98%); they were less successful in raising young from eggs that did hatch (means 58% versus 73%), but this difference was not significant. Their overall breeding success was much lower (about 0.34 fledglings per female versus 1.35). The sex-ratio of breeders was about 127 females to 100 males; about 20% of breeding females did not have male mates. Female Roseate Terns that do not obtain male mates appear to be of low phenotypic ‘quality’ - based on late laying, small clutches and small eggs. Our data support the hypothesis that such females have a higher fitness if they mate with each other and raise a few young than if they do not breed at all.     

Young and female‐biased irruptions in pygmy owls Glaucidium passerinum in southern Finland

Irruptive migrants often show biased sex and age ratio, and typically young females are the most abundant class participating in irruptions. Several hypotheses have been proposed to explain differential migration in birds. We examined these hypotheses in a sexually size‐dimorphic species (females being larger than males), the pygmy owl Glaucidium passerinum, whose migration behaviour has also been poorly documented. Migration data were collected at the Hanko Bird Observatory, SW Finland during 1979–2010. Pygmy owls showed large fluctuations in migration numbers between years. Most of the migrants were young birds and females migrated in larger numbers than males. Results support the ‘territory defence hypothesis’ since males showed weaker tendency to migrate despite the smaller body size, but the ‘dominance hypothesis’ was also supported (subordinate young outnumber dominant adults in migration numbers). Findings support the idea that in owl species, which are dependent on nesting cavities, males show lower migration behaviour than females, whereas the pattern is opposite in species which normally breed outside cavities. In addition, adults migrated later than young, likely because they need to moult remiges before departure. Early hatched young also migrated earlier than late hatched young, suggesting that more dominant young migrate first.     

Ecology and Physiology of Nesting and Early Development of the American Alligator

Ambient temperatures were significantly correlated with alligator(Alligator mississippiensis) nesting activity. Nesting occurredearliest when March-April-May ambient temperatures were highest.Rainfall had no significant relationship with time of nestingactivity although water levels did affect the degree of nesting.The bulk of the nesting took place within a 2-week period eachyear. Nesting chronology and factors affecting nesting were investigatedat Rockefeller Refuge from 1964 through 1987. Courtship activitiesgenerally began in early April and progressively intensifieduntil early June. From late May through the first week of Junecourtship and copulation were intense, the females ovulated,and the high point of spermatogenesis occurred. Factors whichseriously affected nesting success were floods, droughts, andpredation. Salinity levels affected nesting densities alongthe coast. Nesting success (% of nests which produced live hatchlings)averaged 68.3% for 266 nests followed during a 4-yr study. Hatchingsuccess (% of eggs which hatched) averaged 58.2% for 154 nestsfollowed during two nesting seasons. Habitat selection, home ranges, and daily movements were delineatedfor adult males and females. Courtship occurs in deep open waterduring springtime. Adult females selectively seek out densevegetation adjacent to isolated ponds for nesting during thesummer. Adult and sub-adult males tend to prefer open waterall year round and only occasionally venture into the more secludedand heavily vegetated areas used by the females. Home rangesizes and daily movements were much larger for adult males thanfor adult females. Laboratory studies evaluated the effectsof four different egg incubation temperatures on hatching success,sex determination, size at hatching, and growth rates to 18mo of age. The results indicate that incubation temperaturecan have a profound effect on sex ratios, hatchling size, andpost-hatching growth. No significant differences were observedin hatching success at the four different temperatures.     

Lack of sperm production and sperm storage by arctic-nesting shorebirds during spring migration

Birds nesting at high latitudes may copulate during migration to arrive on the nesting grounds ready to breed. We surveyed 12 species of shorebirds during spring migration to determine whether (1) males produced abundant sperm and (2) females harboured functional sperm storage tubules (SSTs). Sperm production by males on migration was rare. Only four of seven species (9.8% of 41 males) of long-distance migrants harboured sperm, whereas all four species (100% of eight males) of short-distance migrants held sperm. In females, no long-distance migrants held sperm in their SSTs ( n  = 28 females) and SSTs were small compared to long-distance migrants collected on their breeding grounds. Our results indicate that shorebirds nesting at high latitudes were generally not reproductively active during migration and that any sexual behaviour on migration is unlikely to lead directly to fertilizations.     

Nesting patterns of European hedgehogs (Erinaceus europaeus) under northern conditions

Little information exists on the nesting of hedgehogs (Erinaceus europaeus) in the harsh northern environment, although this aspect has specific importance for the species’ survival in this region. We studied the nest types and nesting site selection of radio tagged hedgehogs in urban areas in Eastern Finland. Altogether, four different nest types were discovered and one of them (the pre-hibernation nest) is described here for the first time. Hedgehogs preferred residential areas for nesting during the mating and post-mating seasons while in the pre-hibernation season and hibernation period nesting was more common in forest areas. Nest constructions were closely related to materials found in the nest vicinity. During the active period, males used on average 24 nests and changed them 30 times, whereas females used 17 nests and changed them 26 times. The number of female nests and frequency of nest change increased from post-mating to pre-hibernation seasons, while in males both decreased. In general, female and male nests were situated within their established long-term home range, but in the pre-hibernation season over 30 % of male nests were situated outside of it. In post-mating and pre-hibernation seasons, females avoided other individuals of the same sex; this was demonstrated by the lack of nests in other female core areas. Hedgehogs hibernate for around 223 days, which is the longest reported hibernation period for this species. The results of the present study emphasise the importance of forest and diverse residential areas including forest patches for the hedgehog’s nesting habitat.     

Male‐skewed adult sex ratio,survival, mating opportunity and annual productivity in the Snowy Plover Charadrius alexandrinus

Sex differences in adult mortality may be responsible for male‐skewed adult sex ratios and male‐skewed parental care in some birds. Because a surplus of breeding males has been reported in serially polyandrous populations of Snowy Plover Charadrius alexandrinus, we examined sex ratio, early‐season nesting opportunities, adult survival and annual reproductive success of a Snowy Plover population at Monterey Bay, California. We tested the hypotheses that male adult survival was greater than female survival and that a sex difference in adult survival led to a skewed adult sex ratio, different mating opportunities and different annual productivity between the sexes. Virtually all females left chicks from their first broods to the care of the male and re‐nested with a new mate. As a result, females had time to parent three successful nesting attempts during the lengthy breeding season, whereas males had time for only two successful attempts. Among years, the median population of nesting Plovers was 96 males and 84 females (median difference = 9), resulting in one extra male per eight pairs. The number of potential breeders without mates during the early nesting period each year was higher in males than in females. Adult male survival (0.734 ± 0.028 se) was higher than female survival (0.693 ± 0.030 se) in top‐ranked models. Annually, females parented more successful clutches and fledged more chicks than their first mates of the season. Our results suggest that in C. alexandrinus a sex difference in adult survival results in a male‐skewed sex ratio, which creates more nesting opportunities and greater annual productivity for females than for males.     

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.     

A trade-off generated by sexual conflict: Mediterranean wrasse males refuse present mates to increase future success

A variety of mechanisms, including intrasexual competition,intersexual conflict, and physiological constraints, can explainpatterns of reproduction and the adaptive value of specificbehaviors. In a Mediterranean wrasse, Symphodus ocellatus (Labridae),large, nesting males occasionally refuse to spawn with willingfemales in the presence of small, sneaker males. We exploredthe possible adaptive significance of this behavior. Nestingmales refuse females despite the fact that it reduces theirimmediate mating success. This nesting-male behavior also decreasesfemale and sneaker mating success and occurs when sneaker malessurround the nest. Experiments that decreased the number ofsneakers around nests showed that nesting males respond immediatelyto mating opportunities when fewer sneakers are present, andthus they are not simply constrained by a lack of energy orlack of sperm. Experiments that increased the number of sneakersat the nest caused nesting males initially to refuse spawningopportunities, followed by a subsequent decrease in sneakerpresence and an increase in mating rate. We propose that thisbehavior is the result of a trade-off between immediate matingsuccess and future reproduction created by competition betweenmales and conflict between the sexes. Males reduce their immediatemating success by reducing spawning at the nest; sneaker malessubsequently leave, and this decreases mate competition forthe nesting male. Unresponsiveness of nesting males also causessexual conflict between females and nesting males over mating.We argue that this behavior and the existence of a trade-offcan only be understood by examining intersexual conflict andintrasexual competition simultaneously.     

Fat is sexy for females but not males: the influence of body reserves on reproduction in snakes (Vipera aspis)

Reproduction is energetically expensive for both sexes, but the magnitude of expenditure and its relationship to reproductive success differ fundamentally between males and females. Males allocate relatively little to gamete production and, thus, can reproduce successfully with only minor energy investment. In contrast, females of many species experience high fecundity-independent costs of reproduction (such as migration to nesting sites), so they need to amass substantial energy reserves before initiating reproductive activity. Thus, we expect that the relationship between energy reserves and the intensity of reproductive behavior involves a threshold effect in females, but a gradual (or no) effect in males. We tested this prediction using captive vipers (Vipera aspis), dividing both males and females into groups of high versus low body condition. Snakes from each group were placed together and observed for reproductive behavior; sex-steroid levels were also measured. As predicted, females in below-average body condition had very low estradiol levels and did not show sexual receptivity, whereas males of all body condition indices had significant testosterone levels and displayed active courtship. Testosterone levels and courtship intensity increased gradually (i.e., no step function) with body condition in males, but high estradiol levels and sexual receptivity were seen only in females with body reserves above a critical threshold.     

Nesting biology and mating system in an alpine population of Temminck's Stint Calidris temminckii

A colour-marked population of Temminck's Stint Calidris temminckii was studied in an alpine area of southern Norway over 3 years. Birds arrived from late May until late June, and egg-laying occurred over approximately 1 month. Each year, one to three males out of about 15–17 males still displayed after the last recorded clutch-completion date.
There were six documented cases of double-clutching. Inter-clutch intervals varied (range 2–8-9-1 days), longer intervals probably being caused by weather-induced food shortage. A successively bigamous mating pattern was recorded in both sexes. A polygynously (bigamously) mated male invariably incubated its first mate's clutch. Females consistently changed mates between layings of successive clutches, the last one incubated by themselves.
An excess of nesting females was found, particularly in parts of the study area where nesting started late. This appears to have been caused mainly by a considerable annual immigration of late-arriving females, having probably laid their first clutch(es) elsewhere, in nesting habitats that were available earlier. I suggest that male availability is relatively unimportant compared with other factors governing female movements between layings of successive clutches; females may increase their reproductive success, either by achieving a longer egg-laying season (i.e. by moving from nesting habitats/areas available early in the season to those available later) or by being capable of utilizing favourable feeding habitats/conditions in different areas.     

Male response to intruders is related to song characteristics in Darwin’s small tree finch (Camarhynchus parvulus)

Bird song functions in mate choice and species recognition, and hence variation in song can contribute to divergence and reproductive isolation. We used playback experiments to examine male response to conspecific song in Darwin’s small tree finch. Song is a reliable signal of bill morphology in this species, and individuals displayed stronger response to songs of males with similar bill size. These findings suggest that, in the context of territorial defence, males discriminate between intruders on the basis of song characteristics. Given that male response to song may be examined as a proxy for female response, this study also implies that females could discriminate between males on the basis of song. The findings suggest that: (1) perceived threat of intruders is related to reproductive competition and not fighting assessment, and (2) geographical isolation is not required for biologically meaningful song variation in Darwin’s finches.     

Sex-biased dispersal and natal philopatry in the diamondback terrapin, Malaclemys terrapin

Nesting ecology and population studies indicate that diamondback terrapins (Malaclemys terrapin) exhibit nest site fidelity and high habitat fidelity. However, genetic studies indicate high levels of gene flow. Because dispersal affects the genetics and population dynamics of a species, we used six highly polymorphic microsatellite markers to investigate sex-biased dispersal and natal philopatry of M. terrapin in Barnegat Bay, NJ. We compared results of spatial autocorrelation analysis, assignment methods and Wright's F(ST) estimators to a mark-recapture analysis. Mark-recapture analysis over a 4-year period indicated that most individuals have relatively small home ranges (<2 km), with mature females displaying greater home ranges than males. Goodness of fit analysis of our mark-recapture study indicated that some juvenile males were likely transient individuals moving through our study location. Mean assignment indices and first-generation migrant tests indicated that mature males were more prone to disperse than mature females, but first-generation migrant tests indicated that per capita there are more female than male dispersers. Thus, the relative importance of males and females on gene flow in terrapin populations may change in relation to population sex ratios. Spatial autocorrelation analysis indicated that mature females exhibited natal philopatry to nesting beaches, but first-generation migrant tests indicated that a small number of females failed to nest on natal beaches. Finally, we discuss the important conservation implications of male-biased dispersal and natal philopatry in the diamondback terrapin.     

Space use of common genets<Emphasis Type="Italic">Genetta genetta</Emphasis> in a Mediterranean habitat of northeastern Spain: differences between sexes and seasons

The seasonal home range size and spatial relationships of 16 adult genetsGenetta genetta Linnaeus, 1758 (6 males and 10 females) were estimated in a Mediterranean habitat of northeastern Spain. Genets minimum density was estimated as 0.98/km². Mean annual home range was 113.1 ha in males and of 72.0 ha in females. Males had larger home ranges than females in all seasons, but differences were only significant in winter. Home range size changed seasonally and showed a similar pattern in both sexes, with lower values in summer (males — 41.2 ha, females — 29.0 ha) and maximum ones in spring (males — 78.8 ha, females — 56.1 ha). Animals displayed spatial fidelity throughout the year. Core areas (MCP50) represented 27% and 19% of total home range size for males and females, respectively. Resting home ranges (based on locations of inactive animals) were 9 times lower than overall home range size. Individuals of the same sex overlapped less than individuals of different sexes, especially with regard to core areas, which showed almost no overlap. The results obtained suggest that (1) different factors are likely to affect the space use of genets, such as body mass, food abundance and reproductive cycle; (2) genets use space in a heterogeneous way, with areas of greater activity than others within their home range; (3) there was intrasexual segregation with regard to space use.     

Brain and gonadal aromatase activity and steroid hormone levels in female and polymorphic males of the peacock blenny Salaria pavo

In the peacock blenny Salaria pavo large males with well-developed secondary sexual characters establish nests and attract females while small “sneaker” males mimic female sexual displays in order to approach the nests of larger males and parasitically fertilize eggs. These alternative reproductive tactics are sequential, as sneakers irreversibly switch into nesting males. This transition involves major morphologic and behavioral changes and is likely to be mediated by hormones. This study focuses on the role of aromatase, an enzyme that catalyses the conversion of androgens into estrogens, in the regulation of male sexual polymorphism in S. pavo. For this, sex steroid plasma levels and aromatase activity (AA) in gonads, whole brain and brain macroareas were determined in sneakers, transitional males (i.e. sneakers undergoing the transition into nesting males), nesting males and females collected in the field. AA was much higher in ovarian tissue than in testicular tissue and accordingly circulating estradiol levels were highest in females. This supports the view that elevated AA and estradiol levels are associated with the development of a functional ovary. Transitional males are in a non-reproductive phase and had underdeveloped testes when compared with sneakers and nesting males. Testicular AA was approximately 10 times higher in transitional males when compared with sneakers and nesting males, suggesting high AA has a suppressive effect on testicular development. Nesting males had significantly higher plasma levels of both testosterone (T) and 11-ketotestosterone when compared with the other male morphs and previous studies demonstrated that these androgens suppress female-like displays in sneakers. In the brain, AA was highest in macroareas presumably containing hypothalamic nuclei traditionally associated with the regulation of reproductive behaviors. Overall, females presented the highest levels of brain AA. In male morphs AA increased from sneakers, to transitional males, to nesting males in all brain macroareas. These results suggest that the transition into the nesting male tactic is accompanied both by an increase in testicular androgen production and by a higher conversion of androgens into estrogens in the brain. The increase in androgen production is likely to mediate the development of male secondary sexual characters while the increase in brain AA may be related to the behavioral changes associated with tactic transition.     

Home range dynamics,habitat selection,and survival of Greater Roadrunners

ABSTRACT Greater Roadrunners (Geococcyx californianus) are common, poorly studied birds of arid and semi‐arid ecosystems in the southwestern United States. Conservation of this avian predator requires a detailed understanding of their movements and spatial requirements that is currently lacking. From 2006 to 2009, we quantified home‐range and core area sizes and overlap, habitat selection, and survival of roadrunners (N= 14 males and 20 females) in north‐central Texas using radio‐telemetry and fixed kernel estimators. Median home‐range and core‐area sizes were 90.4 ha and 19.2 ha for males and 80.1 ha and 16.7 ha for females, respectively. The size of home range and core areas did not differ significantly by either sex or season. Our home range estimates were twice as large (x?= 108.9 ha) as earlier published estimates based on visual observations (x?= 28–50 ha). Mean percent overlap was 38.4% for home ranges and 13.7% for core areas. Male roadrunners preferred mesquite woodland and mesquite savanna cover types, and avoided the grass‐forb cover type. Female roadrunners preferred mesquite savanna and riparian woodland cover types, and avoided grass‐forb habitat. Kaplan‐Meier annual survival probabilities for females (0.452 ± 0.118[SE]) were twice that estimated for males (0.210 ± 0.108), but this difference was not significant. Mortality rates of male roadrunners were higher than those of females during the spring when males call from elevated perches, court females, and chase competing males. Current land use practices that target woody‐shrub removal to enhance livestock forage production could be detrimental to roadrunner populations by reducing availability of mesquite woodland and mesquite savanna habitat required for nesting and roosting and increasing the amount of grass‐forb habitat that roadrunners avoid.     

Not all who wander are lost: nest fidelity in <Emphasis Type="Italic">Xylocopa virginica</Emphasis> examined by mark recapture

Relocation to novel nests (sometimes called drifting) in flying Hymenoptera is often interpreted as the result of navigation error and guard bees erroneously admitting foreign individuals into the nest. We studied nest fidelity and nest relocation of both females and males in a nesting aggregation of Xylocopa virginica in southern Ontario, Canada, where females can nest either solitarily or socially. Adult female and male bees were trapped at nest entrances, individually paint marked, and then released. Subsequent recapture patterns were used to assess nest fidelity: that is, how faithful individuals were to their home nest and how often they moved to another nest. Bees were considered to have relocated if they were recaptured in a nest different from the one in which they were initially trapped, indicating that they had spent at least one night in a new nest. Some females were only captured in one nest, some occasionally moved to new nests, temporarily or permanently, and a few were never caught in the same nest twice. In addition, females relocated to nests that were further away in 2007 when population density was low, suggesting that they seek out and claim nesting spaces when they are available. Males relocated more frequently than females, with most drifting from nest to nest in no obvious pattern. This indicates that males spend the night wherever space is available or in nests nearest to their territories. This study reveals that for both female and male X. virginica, nest membership is not as stable as once thought.     

Evolution of sexual dichromatism in relation to nesting habits in European passerines: a test of Wallace's hypothesis

Wallace proposed in 1868 that natural rather than sexual selection could explain the striking differences in avian plumage dichromatism. Thus, he predicted that nesting habits, through their association with nest predation, could drive changes in sexual dichromatism by enabling females in cavity nesters to become as conspicuous as males, whereas Darwin (1871, The Descent of Man and Selection in Relation to Sex, John Murray, London) argued that sexual selection was the sole explanation for dichromatism. Sexual dichromatism is currently used as indicating the strength of sexual selection, and therefore testing Wallace's claim with modern phylogentically controlled methodologies is of prime interest for comparing the roles of natural and sexual selection in affecting the evolution of avian coloration. Here, we have related information on nest attendance, sexual dichromatism and nesting habits (open and cavity nesting) to male and female plumage conspicuousness in European passerines. Nest incubation attendance does not explain male or female plumage conspicuousness but nest type does. Moreover, although females of monochromatic and cavity nesting species are more conspicuous than females of other species, males of monochromatic and open nesting species are those with more cryptic plumage. Finally, analyses of character evolution suggest that changes in nesting habits influence the probability of changes in both dichromatism and plumage conspicuousness of males but do not significantly affect those in females. These results strongly suggest a role of nesting habits in the evolution of plumage conspicuousness of males, and a role for sexual selection also in females, both factors affecting the evolution of sexual dichromatism. We discuss our findings in relation to the debate that Darwin and Wallace maintained more than one century ago on the importance of natural and sexual selection in driving the evolution of plumage conspicuousness and sexual dichromatism in birds, and conclude that our results partly support the evolutionary scenarios envisaged by both extraordinary scientists.