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Alternative reproductive tactics and strategies (ARTS) refer to polymorphic reproductive behaviours in which in addition to the usual two sexes, there are one or more alternative morphs, usually male, that have evolved the ability to circumvent direct intra-sexual competition. Each morph has its own morphological, ecological, developmental, behavioural, life-history, and physiological profile that shifts the balance between reproduction and self-maintenance, one aspect being immunity. Immunoecological work on species with ARTS, which is the topic of this review, is particularly interesting because the alternative morphs make it possible to separate the effects of sex per se from other factors that in other species are inextricably linked with sex. We first summarize the evolution, development, and maintenance of ARTS. We then review immunoecological hypotheses relevant to species with ARTS, dividing them into physiological, life-history, and ecological hypotheses. In context of these hypotheses, we critically review in detail all immunoecological studies we could find on species with ARTS. Several interesting patterns emerge. Oddly, there is a paucity of studies on insects, despite the many benefits that arise from working with insects: larger sample sizes, simple immune systems, and countless forms of alternative reproductive strategies and tactics. Of all the hypotheses considered, the immunocompetence handicap hypothesis has generated the greatest amount of work, but not necessarily the greatest level of understanding. Unfortunately, it is often used as a general guiding principle rather than a source of explicitly articulated predictions. Other hypotheses are usually considered a posteriori, but perhaps they should take centre stage. Whereas blanket concepts such as “immunocompetence” and “androgens” might be useful to develop a rationale, predictions need to be far more explicitly articulated. Integration so far has been a one-way street, with ecologists delving deeper into physiology, sometimes at the cost of ignoring their organisms’ evolutionary history and ecology. One possible useful framework is to divide ecological and evolutionary factors affecting immunity into those that stimulate the immune system, and those that depress it. Finally, the contributions of genomics to ecology are being increasingly recognized and sometimes applied to species with ARTS, but we must ensure that evolutionary and ecological hypotheses drive the effort, as there is no grandeur in the strict reductionist view of life.

IntroductionObesity is a major threat to global health. When more conventional methods have failed, obesity can be addressed via bariatric surgery. Here we examine the reasons why patients choose bariatric surgery and the behavioral consequences thereafter.MethodsA qualitative study with a phenomenological design was used to analyze detailed interview responses from recipients of bariatric surgery.ResultsBefore surgery, (a) bariatric surgery was chosen for obvious reasons: patients had been overweight, had obesity-related health problems, and had difficulties moving. (b) Information was obtained from medical practitioners and online discussion groups. (c) Fear, anxiety, and apprehension were common. Friends and family were sometimes supportive and sometimes disapproving. After surgery, (1) many chronic health problems disappeared or eased significantly. (2) Subjects had difficulties adjusting to small portions and altered food preferences. (3) Physical activity increased. (4) Self-esteem increased but the worry of regaining the weight remained. (5) As before surgery, there were both supportive and condemning attitudes by relatives, friends, and society. (6) A desire for further nutritional and psychological counseling was indicated. (7) Relationships and quality of sex improved in most cases but not always. Single women, particularly, became more active in potential relationships.DiscussionWith a few exceptions, our results agree with the literature, supporting the idea that bariatric surgery leads to extensive physical, psychological, and social changes. Hence, patients ought to be better prepared for these changes, and medical practitioners ought to be aware of the magnitude of the changes this surgery will bring about in their patients’ lives.

Can ideas about the regulation of body mass in birds be used to explain the breakdown of regulation associated with obesity and anorexia in humans? There is no evidence to think so. Medicine can always benefit from the application of evolutionary ecology ideas, but we must be prepared to dismiss these ideas when they just do not fit the data.

Animals use multiple cues when choosing mates, but it is not yet clear why a single signal would not suffice. In this paper, drawing support from predation and “noise” effects on mate choice, marketing economics, and multiple signals models, a new hypothesis explaining multiple sexual signals is proposed: the sexual interference hypothesis. The hypothesis is based on three well-supported premises: (1) selectivity decreases when mate assessment costs increase, (2) assessment costs increase when the propagation or reception of sexual signals is more difficult, and (3) males not only exploit such circumstances by courting females when choice is more difficult, but actively interfere with females' preferences by making choice more difficult. The hypothesis argues that additional sexual signals evolve as a way for males to hinder female mate choice by interfering with the propagation and reception of other males' sexual signals. Females respond by evolving the ability to glean meaningful information from signals despite males' attempts at obfuscation. In turn, males respond by producing better interference signals and signals that are not so easily blocked. This co-evolutionary process increases the costs of assessment for females and the costs of signal production for males, and leads to a temporary equilibrium of honest advertising via multiple signals.

Anorexia nervosa is diagnosed by drastic weight loss, a fear of gaining weight, a distorted body image, and, in women, three consecutive episodes of amenorrhea. It is often associated with a compulsive need for exercise, a bright outlook on life, and a high level of competitiveness. It afflicts primarily young women in higher socioeconomic strata who are highly competitive and otherwise overachievers. There are three adaptive explanations for anorexia nervosa: the reproductive suppression, the fleeing famine and the pseudo-female hypotheses. Here I present a novel hypothesis, the age-related obesity hypothesis. It posits that the otherwise normal tendency by women to seek a youthful appearance can become maladaptive and lead to anorexia nervosa in environments in which thinness becomes the primary indicator of youth, such as in modern industrialized societies. This hypothesis explains the aforementioned associated features of anorexia nervosa, and its increasing prevalence in western societies. The hypothesis generates several testable predictions: (1) Prevalence of anorexia nervosa across societies should be related to the degree to which thinness is an indicator of youth in a population. (2) Conversely, perceptions of the weight-age relationship should differ among populations depending on the prevalence of anorexia nervosa. (3) Anorectic individuals, or those with the propensity to develop the disease, should have a biased perception of the weight-age relationship. (4) Experimental manipulation of individuals' perception of the weight-age relationship should affect weight concerns, particularly among anorectic or at-risk individuals. Should the hypothesis be supported it might be used to screen at-risk individuals. Furthermore, it would call for more integrative public health programs that take a comprehensive approach encompassing both obesity and anorexia.

Abstract The immune system is costly to operate, so we expect allocation to this function to relate to other indices of overall phenotypic condition. In captive male ruffs (Philomachus pugnax), we examine covariation between three seasonal male characteristics induced by testosterone (neck 'ruff', facial wattles, and increases in mass/size) and cell-mediated and humoral immunity. The ruff has two genetically distinct morphs of males, 'independents' and 'satellites', which differ in mating behaviour, somewhat in body size, and possibly life history strategy. Ruff length and wattle number were significantly correlated with each other and with body size, but unrelated to mass/size. Humoral immunity was weakly correlated with size, but not with secondary male traits, or with cell-mediated immunity. We did not detect differences in humoral immunity between morphs. Cell-mediated immunity was weakly correlated with ruff length, but not with wattle number, size, or mass/size. Cell-mediated immunity decreased significantly with age. Controlling for age, independents had higher cell-mediated immunity responses than satellites. The expected relationships between two measures of immune function and other measures of condition were not always present, which suggests we need more data and/or more specific predictions about how the different aspects of immune function relate to each other and to ecological variables.

The immune system is an energetically expensive self–maintenance complex that, given the risks of parasitism, cannot be carelessly compromised. Life–history theory posits that trade–offs between fitness components, such as self–maintenance and reproduction, vary between genders and age classes depending on their expected residual lifetime reproductive success, and seasonally as energetic requirements change. Using ruff ( Philomachus pugnax ), a bird with two genetically distinct male morphs, we demonstrate here a decrease in male immunocompetence during the breeding season, greater variance in immune response among males than females, immunosenescence in both sexes and male morphs, and a seasonal shift in the age range required to detect senescence. Using a phytohaemagglutinin delayed hypersensitivity assay, we assessed cell–mediated immunity (CMI) of males of typical breeding age during the breeding and nonbreeding seasons, and of a larger sample that included females and birds of a greater age range during the non-breeding period. CMI was higher for breeding–aged males in May than in November, but the increase was not related to age or male morph. In November, mean CMI did not differ between the sexes, but the variance was higher for males than for females, and there were no differences in mean or variance between the two male morphs. For both sexes and male morphs, CMI was lower for young birds than for birds of typical breeding ages, and it declined again for older birds. In males, senescence was detected in the non–breeding season only when very old birds were included. These results, generally consistent with expectations from life–history theory, indicate that the immune system can be involved in multifarious trade–offs within a yearly cycle and along an individual9s lifetime, and that specific predictions about means and variances in immune response should be considered in future immunoecological research.

The fact that avian eggs contain antibody of maternal origin is well documented, but only recently has this phenomenon been considered in an ecological context. We used tree swallows (Tachycineta bicolor) to examine the possibility of transgenerational immunity and its effect on nestling growth and immune development. We measured cell-mediated immunity with a delayed-hypersensitivity assay and antibody-mediated immunity with a hemagglutination test with sheep red blood cells (SRBCs). We tested for differences in immunocompetence and growth between nestlings from females who had been exposed to a novel antigen prior to egg laying and nestlings from unexposed females. To determine whether the effect, if any, resulted from something transferred to the eggs prior to egg laying or from subse - quent changes in parental behaviour, nestlings were exchanged so that at each nest half the nestlings were from fe - males who had been injected with SRBCs and half were from females who had not been exposed to SRBCs. Finally, brood sizes were independently manipulated to either 4 or 6 nestlings. We failed to detect maternal antibodies in any nestlings, and whether a female was exposed to SRBCs or not had no effect on the growth or cell-mediated immunity of her brood. However, nestlings in smaller broods grew better than nestlings in larger broods, though we did not find the expected differences in cell-mediated immunity. Furthermore, within each nest, nestlings whose mothers had been exposed to SRBCs grew better than nestlings whose mothers had not been exposed. These results are contrary to the idea of a simple trade-off in the allocation of resources between parasite protection and reproduction; however, they support the idea that exposure of females to parasites prior to egg laying leads to better nestling growth, and are con- gruous with the possibility of mithridatic parental care. Resume : La presence d'un anticorps d'origine maternelle dans les oeufs des oiseaux est un fait bien connu, mais ce n'est que recemment que ce phenomene a ete examine dans un contexte ecologique. Nous avons utilise des hirondelles bicolores (Tachycineta bicolor) pour verifier l'existence possible d'une immunite transmise d'une generation a l'autre et ses effets eventuels sur la croissance des oisillons au nid et sur le developpement de leur systeme immunitaire. Nous avons mesure l'immunite d'origine cellulaire au cours d'un test d'hypersensibilite retardee et l'immunite assuree par les anticorps au moyen d'un test d'hemagglutination SRBCs (globules rouges de mouton standardises). Nous avons cherche a etablir s'il y a des differences dans l'immunocompetence et la croissance chez les oisillons issus de femelles expo- sees a un antigene nouveau avant la ponte et chez les oisillons de femelles non exposees. Pour determiner si cet effet, s'il existe, resulte d'un transfert aux oeufs avant la ponte ou des changements subsequents dans le comportement pa- rental, les oisillons ont ete deplaces de telle sorte que, dans chaque nid, la moitie des oisillons etaient issus de femelles qui avaient recu une injection de SRBC et la moitie, issus de femelles non exposees aux SRBCs. Enfin, les couvees ont ete fixees independammen ta4o u 6o isillons. Nous n'avons detecte d'anticorps maternel chez aucun des oisillons et l'exposition d'une femelle a des SRBCs est sans effet sur la croissance ou l'immunite d'origine cellulaire de sa pro - geniture. Cependant, les oisillons des couvees moins nombreuses se developpent mieux que les oisillons des couvees plus grandes, mais nous n'avons pas observe les differences prevues quant a l'immunite d'origine cellulaire. De plus, dans chaque nid, les oisillons issus de meres exposees aux SRBCs ont eu une croissance meilleure que celle des oisil- lons issus de meres non exposees. Ces resultats contredisent l'hypothese d'un simple compromis dans l'allocation des ressources entre la protection contre les parasites et la reproduction, mais ils sont en accord avec l'hypothese selon la - quelle l'exposition aux parasites avant la ponte donne lieu a une meilleure croissance des oisillons et ne contredisent pas la possibilite de soins parentaux mithridatiques. (Traduit par la Redaction) 925

SAD is a state of depression induced by a lack of sufficient sunlight that occurs at high latitudes during the fall and winter. SAD causes people to be risk-adverse. Granting agencies of high latitude countries should time high-risk research competitions so they do not coincide with the SAD months.

Endler (1980) suggested that in a carotenoid-poor envi-ronment, carotenoid-dependent sexual ornamentsindicateforaging ability, and hence, they can be used by femalesto gauge male quality. This idea led researchers to viewfemale mate choice from a fresh perspective, and it gaineda fair level of acceptance (Kodric-Brown 1989; Milinskiand Bakker 1990; Houde and Torio 1992; Frischknecht1993); however, many years passed before the “carotenoid-poor-environment” assumption began to be questioned(Hudon 1994; Linville and Breitwisch 1997; Grether et al.1999) or a viable alternative hypothesis was first conceived(Lozano 1994). Carotenoids stimulate the immune system,prevent cancer, and act as free radical scavengers (Ames1983; Bendich and Olson 1989; Di Mascio et al. 1991;Diplock 1991). These physiological functions had not beenconsidered in the ecological literature and led to the al-ternative hypothesis that carotenoid-dependentornamentsactually indicate the bearer’s immune condition and healthstatus (Lozano 1994). Lozano’s hypothesis was recentlyexpanded and generalized by Von Schantz et al. (1999),who proposed that sexual signals, carotenoid dependentor not, indicate resistance to oxidative stress. Hill (1999)recently outlined several alleged inconsistencies that “havebeen ignored or overlooked in the growing literature pro-moting the idea of carotenoids as signals of immuno-competence,” but his arguments and supporting evidencerequire careful scrutiny.First, Hill (1999) aptly titles a subsection “Comparing

Theoretical models view biparental care as a state of equilibrium that can be maintained only when the amount of parental care provided by one parent depends on the amount provided by its mate. According to these models, biparental care results when a decrease in the contribution of one parent is partially, but not completely, compensated for by an increase in the contribution of the other parent. Furthermore, this equilibrium state can only be stable if any other external factor affects male and female effort equally. We used yellow warblers (Dendroica petechia) to examine whether changes in brood size and food abundance affect the parental contributions of the sexes equally. Supplemental food did not affect parental care by either sex, but brood size did. Both males and females provided more to larger broods, and in large broods only, their provisioning rates increased with nestling age. Parental effort per nestling was similar in the two sexes, being higher for smaller broods and increasing with nestling age. Based on brood biomass, parental effort was greater for smaller broods, and decreased with nestling age in females only. Therefore, in agreement with current models of the maintenance of biparental care, the effects of brood size and nestling age on parental care did not differ significantly between the sexes. Nonetheless, data from other species and theory indicate that the costs and benefits of providing parental care differ between the sexes, so it is unlikely that biparental care can be maintained solely by a partial compensation response.

Using morphological or behavioural features correlated with paternal care, females can, prior to mating, assess the potential parental contribution of males. As a first step in a study of female mate choice in yellow warblers, this study was designed to examine the importance of paternal care by males of differing chest striping. Contrary to a previous report, paternal care was not negatively correlated with male chest striping. Paternal care was highly variable between individuals. Females did not compensate for experimentally induced reductions of paternal care, which resulted in significantly reduced nestling growth. Therefore, in the absence of alternative mating opportunities, males must maintain their contributions of paternal care or pay the cost of reduced fitness.

Emlen and Oring (1977) suggested that monogamy in birds is maintained because of the need for strict biparental care. A corollary of their suggestion is that paternal care should decrease under conditions of high food abundance. An alternative is that paternal care would increase if males take advantage of the higher food abundance by trying to reduce the length of the nestling feeding period. We tested these two ideas using yellow warblers (Dendroica petechia) by providing some pairs with supplemental food, thereby reducing the importance of biparental care. However, the extra food did not decrease paternal effort, nor did it increase it (Fig. 2). Early in the nestling period experimental females brooded more but visited their nestlings less than did control females, but later, when brooding times decreased, experimental females fed their nestlings more than did control females (Fig. 3). There were no significant differences in nestling survival (Fig. 5), but nestlings in the control treatment were larger and heavier up to 6 days old (Fig. 6). The main effect of supplemental food was on maternal, not paternal behaviour. Models of biparental care assume interdependence between the parental effort of both parents. In this species, however, males and females provide for their brood independently from each other.

Male tree swallow (Tachycineta bicolor) territory owners and floaters were compared in terms of size and nutritional condition to test the resource holding potential hypothesis. Owners were larger than floaters when compared using six morphological measurements. There were no differences in dry mass, ash, or fat content, but territory owners were heavier and had larger protein reserves than floaters. Territory owners may be those individuals who win intrasexual conflicts for the possession of nest boxes, or those who, because of their better nutritional condition, can arrive at the breeding grounds earlier to secure a territory.

Evolutionary explanations, many of which have appeared on the pages of this journal, are becoming more pervasive and influential in medicine, so it is becoming more important to understand how these types of explanations differ from the proximate approach that is more common in medicine, and how the evolutionary approach can contribute to medicine. Understanding of any biological phenomenon can occur at four levels: (1) ontogeny (2) causation, (3) function and (4) evolution. These approaches are not mutually exclusive, and whereas the first two are more common in medical practice, a complete explanation requires all four levels of analysis. Two major differences among these approaches are the apparent degree of immediacy associated with them, and the extent to which they apply to individuals rather than populations. Criticisms of adaptive explanations often arise from a failure to understand the complementary nature of these four types of explanations. Other unwarranted criticisms result from a failure to appreciate that adaptive explanations often apply to populations, not individuals. A third type of criticism is driven by the mistaken belief that adaptive explanations somehow justify morally reprehensible behaviours. Finally, evolutionary explanations sometimes face the criticism of "personal incredulity". Adaptive explanations must be consistent with basic evolutionary concepts and must adhere to the physical reality of the phenomenon in question. Their value, however, comes not in devising a seemingly rational explanation, but in their predictions. Testable predictions must be explicitly stated and clearly articulated. They must differ from those of arising from other hypotheses and must not only be interesting to evolutionary biologists, but also useful to medical practitioners. Integration of the proximate and the ultimate approaches is possible and potentially beneficial to both evolutionists and physicians, but it requires some basic understanding of our differences and a desire to co-operate.

Vigil summarizes sex-related differences in emotivity, and presents a psychological model based on the restrictive assumption that responses to stimuli are dichotomous. The model uses for support the concept of intrasexual selection, but ignores intersexual selection. An alternative hypothesis might be that emotivity signals age: maturity in men and youth in women. Integration requires considering all evolutionary biology, not just agreeable concepts.

Publisher Summary Along with competition and predation, parasitism is one of the main sources of biotic stress facing all organisms. Recently, it has become recognized that animal diets may also be shaped by the need for protection from parasites. Foraging behavior evolves primarily to meet the need of a nutritionally adequate diet. However, just as foraging behavior can be affected by predators and competitors, some features of diet selection seem to have evolved to stave off or reduce parasitism. These adaptations can include the avoidance of foods that are also potential sources of parasitic infection, the use of prophylactic substances, and the consumption of therapeutic substances. This chapter incorporates self-medication into the broader phenomena—namely, the effects of plant chemicals across several trophic levels—and categorizes self-medicating behavior into two basic forms: prophylactic and therapeutic. It reviews evidence in the published literature for the occurrence of self-medication in nonhuman vertebrates. The chapter also discusses behavioral mechanisms that may play a role in self-medication and highlights potential implications for other areas of research.

It has been argued that intraspecific mate-choice copying can be adaptive under certain conditions. Dugatkin's (1992, Am. Nat.139, 1384-1389) work with guppies, Poecilia reticulataremains the most influential experimental demonstration of this phenomenon. We replicated Dugatkin's work using several choice criteria to ensure that our results were not dependent upon any single method of judging mate choice. We also tested our findings against two null hypotheses of differing stringency. Irrespective of the choice criteria or null hypothesis used, we did not observe any relationship between female mate choice and copying. We conclude that further experimental evidence of female mate-choice copying is required before the existence of this behaviour can be affirmed.1997The Association for the Study of Animal Behaviour

The role of parasitism has, to date, been largely ignored in optimal foraging theory. The mechanisms necessary to allow animals to use their diet to protect themselves from potential or actual parasitism have been observed in various species. The inclusion of the effects of parasitism on diet choice may considerably improve the predictive powers of future optimal foraging models

In recent years carotenoids have become increasingly important in the study of sexual selection. Endler (1980) found that the colour pattern diversity and conspicuousness of males of a population of guppies (Poecilia reticulata) increased after a few generations without predation. He argued that males, emancipated from the constraints of predation, were able to respond better to sexual selection brought about by female preference for colourful males. He subsequently (Endler 1983) showed that in the early stages of courtship females prefer males with more red spots. Kodric-Brown (1985) and Houde (1987) later confirmed these results. Finally, Kodric-Brown (1989) showed that, as previously thought, dietary carotenoids affect male guppy coloration and, as a consequence, female preference. Analogous results have been found in other taxa. Female house finches (Carpodacus mexicanus) prefer males with redder plumage (Hill 1990). Zuk et al. (1990a) found that red jungle fowl (Gallus gallus) females prefer males with redder combs. Milinski and Bakker (1990) found a positive correlation between the intensity of male coloration and female preference in the three-spined stickleback (Gasterosteus aculeatus). In these three species the expression of the traits being used by females to select males depends partially on dietary carotenoids (Brush and Power 1976, Rothschild 1973, Brush and Reisman 1965, respectively). Endler's (1980) explanation has always been embraced when interpreting these results. Endler (1980) suggested that, by choosing mates based on a carotenoid-dependent trait, females choose superior mates. He argued that, because these males are able to obtain carotenoids from a carotenoid-poor environment, they are better foragers, and, because they are more conspicuous, they must also be better at avoiding predators. In recent years carotenoids have also aroused the attention of nutritionists, immunologists and oncologists. Carotenoids are currently recognized not only as an essential part of a normal diet (e.g. Simpson and Chichester 1981, Goodwin 1986), but also as free radical scavengers (e.g. Burton 1989, Olson 1989, Sueki 1991), stimulants of the immune system (e.g. Alexander et al. 1985, Bendich and Shapiro 1986, Olson 1989, Prabhala et al. 1990, Jyonouchi et al. 1991, Sueki 1991, Watson et al. 1991; see reviews by Bendich 1989a, b), and even as potential prophylactics against cancer (e.g. Modan et al. 1981, Mathews-Roth 1982, Santamaria et al. 1983, MathewsRoth and Krinsky 1985, Trechsel et al. 1985, Schoen and Watson 1988, Schwartz and Shkalr 1988, Olson 1989, Wang et al. 1989, El Attar and Lin 1991, Sueki 1991; see reviews by Ames 1983, Olson 1986, Ritenbaugh 1987, Temple and Basu 1988, Connett et al. 1989, Krinsky 1989, Ziegler 1989). This rise in the interest in carotenoids in nutritional and medical circles not only parallels, but might also be closely related to the study of sexual selection. In terms of sexual selection an intricate picture emerges if these functions of carotenoids are considered. By choosing males based on carotenoid-dependent traits, females may not be merely choosing males who are good foragers and efficient at avoiding predators. Females might also be increasing the likelihood that their mates are not only healthy, but also better able to deal with any future health problems. The benefits to females would be a lower risk of getting pathogens from their mates, and a greater likelihood that males will be able to provide adequate paternal care if such care is required. Ties with Hamilton and Zuk's (1982) hypothesis on the role of parasites in sexual selection are immediately apparent. For the purposes of this discussion, parasites are broadly and functionally defined as any organisms living in or on, as well as lowering the fitness of a heterospecific animal. Hamilton and Zuk (1982) proposed an explicit mechanism by which Zahavi's (1975) handicap principle could work: they suggested that male secondary sexual traits used by females to choose males indicate heritable variation in parasite resistance. If the immuno-stimulant effects of carotenoids are considered (see references

When a group of individuals creates something, credit is usually divided among them. Oddly, that does not apply to scientific papers. The most commonly used performance measure for individual researchers is the h-index, which does not correct for multi-authorship. Each author claims full credit for each paper and each ensuing citation. This mismeasure of achievement is fuelling a flagrant increase in multi-authorship. Several alternatives to the h-index have been devised, and one of them, the individual h-index (hI), is logical, intuitive and easily calculated. Correcting for multi-authorship would end gratuitous authorship and allow proper attribution and unbiased comparisons., Comment: 7 pages

We relate features of the breeding dispersions and site fidelity of American redstarts (Setophaga ruticilla) to breeding success and interpret the findings in terms of sexual selection. One-year-old male redstarts show delayed plumage maturation, making male dispersions particularly easy to appreciate. In our study site in New Brunswick, Canada, older males usually arrived early each breeding season and gathered in contiguous territories or neighborhoods, while subadult males arrived later and settled peripherally to the adults. Subadult males constituted about 40% of the male population, on average, yet only 5% of banded nestlings returned to the natal breeding ground. Also, newly adult males, 2 years old or more, constituted about 15% of all males. Nearly 50% of adult males returned, twice the return rate of subadults. Among returns, older males returned more often to the same territory than did those that were subadult the previous year. Regardless of age, returns of males in a subsequent year were predicted more by the duration of their stay on the breeding territory than reproductive success. Males outnumbered females. Females returned less often than their mates, but more often if they had fledged young. Females rarely returned to the same mate or territory, but often returned to the same vicinity. The subadult males seem to represent a special dispersive phase of the life history. The evidence indicates strong competition among males for territories and females, older males being more often successful in both circumstances.