Relative contributions of fixed and dynamic heterogeneity to variation in lifetime reproductive success in kestrels (Falco tinnunculus)

Many species show large variation in lifetime reproductive success (LRS), with a few individuals producing the majority of offspring. This variation can be explained by factors related to individuals (fixed heterogeneity) and stochastic differences in survival and reproduction (dynamic heterogeneity). In this study, we study the relative effects of these processes on the LRS of a Dutch Kestrel population, using three different methods. First, we extended neutral simulations by simulating LRS distributions of populations consisting of groups with increasingly different population parameters. Decomposition of total LRS variance into contributions from fixed and dynamic heterogeneity revealed that the proportion of fixed heterogeneity is probably lower than 10% of the total variance. Secondly, we used sensitivities of the mean and variance in LRS to each parameter to analytically show that it is impossible to get equal contributions of fixed and dynamic heterogeneity when only one parameter differs between groups. Finally, we computed the LRS probability distribution to show that even when all individuals have identical survival and reproduction rates, the variance in LRS is large (females: 27.52, males: 12.99). Although each method has its limitations, they all lead to the conclusion that the majority of the variation in kestrel LRS is caused by dynamic heterogeneity. This large effect of dynamic heterogeneity on LRS is similar to results for other species and contributes to the evidence that in most species the majority of individual variation in LRS is due to dynamic heterogeneity.     

Laboratory relationships between adult lifetime reproductive success and fitness surrogates in a Drosophila littoralis population

The difficulties in measuring total fitness of individuals necessitate the use of fitness surrogates in ecological and evolutionary studies. These surrogates can be different components of fitness (e.g. survival or fecundity), or proxies more uncertainly related to fitness (e.g. body size or growth rate). Ideally, fitness would be measured over the lifetime of individuals; however, more convenient short-time measures are often used. Adult lifetime reproductive success (adult LRS) is closely related to the total fitness of individuals, but it is difficult to measure and rarely included in fitness estimation in experimental studies. We explored phenotypic correlations between female adult LRS and various commonly used fitness components and proxies in a recently founded laboratory population of Drosophila littoralis. Noting that survival is usually higher in laboratory conditions than in nature, we also calculated adjusted adult LRS measures that give more weight to early reproduction. The lifetime measures of fecundity, longevity, and offspring viability were all relatively highly correlated with adult LRS. However, correlations with short-time measures of fecundity and offspring production varied greatly depending on the time of measurement, and the optimal time for measurement was different for unadjusted compared to adjusted adult LRS measures. Correlations between size measures and adult LRS varied from weak to modest, leg size and female weight having the highest correlations. Our results stress the importance of well-founded choice of fitness surrogates in empirical research.     

Lifetime reproductive success, longevity, and reproductive life history of female yellow baboons (Papio cynocephalus) of Mikumi National Park, Tanzania

The relationship between longevity and lifetime reproductive success (LRS) was studied in free-ranging female baboons of Mikumi National Park, Tanzania. A severe population decline occurred between the 12th and 20th years of the study. The total sample consisted of 72 females born and reaching adulthood before the start of the population decline. There were 27 females who were adult at the start of the study and 45 who became adult within the 12 years prior to the decline. The subjects were studied until all 72 were dead and all of their offspring were either dead or at least six years old; this took 24 years. The relationship of longevity to LRS was statistically significant for the total sample and for both sub-samples, with 70% of the total variance in LRS accounted for by longevity. Longevity was linked to LRS via a chain of statistically significant relationships: The longer the life span, the longer the reproductive life; the longer the reproductive life, the more offspring produced; the more offspring produced, the higher the LRS. Mean LRS, life span, and reproductive longevity all differed between the two sub-samples. Since the sub-samples were time-linked to a population decline affecting longevity, either sub-sample separately would fail to reflect the broader picture. This illustrates the importance of appreciable sample sizes from long-term studies in helping understand the dynamics between life history estimates and ecological conditions in variable environments.     

Are there indirect fitness benefits of female extra-pair reproduction? Lifetime reproductive success of within-pair and extra-pair offspring

The forces driving extra-pair reproduction by socially monogamous females, and the resulting genetic polyandry, remain unclear. A testable prediction of the hypothesis that extra-pair reproduction partly reflects indirect selection on females is that extra-pair young (EPY) will be fitter than their within-pair young (WPY) maternal half-siblings. This prediction has not been comprehensively tested in a wild population, requiring data on the lifetime reproductive success (LRS) of maternal half-sib EPY and WPY. We used 17 years of genetic parentage data from song sparrows, Melospiza melodia, to compare the LRS of hatched EPY and WPY maternal half-siblings measured as their lifetime number of hatched offspring, recruited offspring, and hatched grandoffspring. EPY hatchlings were not significantly fitter than WPY hatchlings for any of three measures of LRS. Furthermore, opposite to prediction, EPY hatchlings tended to have lower LRS than their maternal half-sibling WPY hatchlings on average. EPY also tended to be less likely to survive to hatch than their maternal half-sibling WPY. Taken together, these results fail to support one key hypothesis explaining the evolution of genetic polyandry by socially monogamous females and suggest there may be weak indirect selection against female extra-pair reproduction in song sparrows.     

Mating system, sexual dimorphism, and the opportunity for sexual selection in a territorial ungulate

In mammals, species with high sexual size dimorphism tend tohave highly polygynous mating systems associated with high variancein male lifetime reproductive success (LRS), leading to a highopportunity for sexual selection. However, little informationis available for species with weak sexual size dimorphism. Ina long-term study population, we used parentage analysis basedon 21 microsatellite markers to describe, for the first time,variance in male lifetime breeding success (LBS) of roe deer,a territorial ungulate where males weigh less than 10% morethan females. LBS ranged from 0 to 14 (mean = 4.54, variance= 15.5), and its distribution was highly skewed, with only afew males obtaining high LBS and many males failing to breedor siring only one fawn. As predicted for polygynous specieswith low sexual size dimorphism, the standardized variance inmale LBS was low (I_m = 0.75) and was only slightly higher thanthe standardized variance in female LRS (I_f = 0.53), suggestinga low opportunity for sexual selection. The I_m value reportedhere for roe deer is much lower than values reported for highlydimorphic ungulates such as red deer (I_m > 3). We suggestthat, along a continuum of opportunity for sexual selection,roe deer occupy a position closer to monogamous and monomorphicterritorial ungulates than to highly polygynous, sexually dimorphicungulates with dominance rank–based mating systems suchas harems or roving mating systems.     

Increased lifetime reproductive success of first‐hatched siblings in Common Kestrels Falco tinnunculus

Order of birth has profound consequences on offspring across taxa during development and can have effects on individuals later in life. In birds, differential maternal allocation and investment in their progeny lead to variance in the environmental conditions that offspring experience during growth within the brood. In particular, laying and hatching order have been proposed to influence individual quality during the growing period, but little is known about the fitness consequences that these two factors have for offspring from a lifetime perspective. We explored the effect of laying and hatching order on post‐fledgling survival (measured as recruitment probability) and lifetime reproductive success (LRS) in Common Kestrels Falco tinnunculus, using a long‐term and individual‐based dataset. First‐hatched chicks showed higher survival probability and LRS than their siblings. This effect was not due to body condition of the individuals at adulthood, the quality of their mates or the reproductive outcome compared with later‐hatched individuals. Instead, first‐hatched chicks had a higher recruitment probability. This could be explained by the higher body condition attained by first‐hatched chicks at the end of the nesting period, perhaps due to an enhanced competitive advantage for food over their siblings at the time of hatching. Laying order, in contrast to hatching order, appeared to have little or no effect on LRS. Our results suggest that hatching order within siblings predicts fitness, and that better early‐life conditions during growth experienced by first‐hatched chicks improve first survival and then recruitment, resulting in an enhanced LRS.     

Lifetime offspring production in relation to breeding lifespan, attractiveness, and mating status in male collared flycatchers

As a comprehensive fitness parameter, lifetime reproductive success (LRS) is influenced by many different environmental and genetic factors, among which longevity is one of the most important. These factors can be reflected in secondary sexual characters, which may affect the life histories of individuals via social relations with conspecifics. Facultative polygyny in birds is another conspicuous reproductive trait that potentially increases male reproductive success, but lifetime success data in relation to polygyny are scarce. Here, we used 17?years of breeding data to quantify the LRS of male collared flycatchers (Ficedula albicollis) on the basis of lifetime recruitment of offspring. Breeding lifespan showed a positive relationship with LRS, and it was also significantly associated with mean recruitment of offspring per breeding year. Body size and sexually selected forehead patch size did not predict the number of recruits. Polygyny was positively associated with LRS, but when we corrected for lifespan, this relationship disappeared. Our results demonstrate that the relationship between longevity and LRS is not explained by the higher number of reproductive attempts when living longer, and question the adaptive value of polygyny in this population. The lack of association between forehead patch size and recruitment suggests that forehead patch is a poor indicator of phenotypic quality in our birds.     

Lifetime reproductive success,selection on lifespan,and multiple sexual ornaments in male European barn swallows

Natural and sexual selection arise when individual fitness varies according to focal traits. Extra‐pair paternities (EPPs) can affect the intensity of selection by influencing variance in fitness among individuals. Studies of selection require that individual fitness is estimated using proxies of lifetime reproductive success (LRS). However, estimating LRS is difficult in large, open populations where EPPs cause reallocation of biological paternity. Here, we used extensive field sampling to estimate LRS in a population of barn swallows (Hirundo rustica) to estimate selection on lifespan and ornamental traits of males. We found selection on lifespan mediated both by within‐ and extra‐pair fertilization success and selection on tail length mediated by within‐ but not extra‐pair fertilization success. In addition, we found selection on tail white spots via extra‐pair fertilization success after controlling for selection on other traits. These results were not confounded by factors that hamper studies of LRS, including nonexhaustive sampling of offspring and biased sampling of males. Hence, natural and sexual selection mediated by LRS operates on lifespan, tail length, and size of the tail white spots in barn swallows.     

Spatio-temporal variation of natural and sexual selection in breeding populations of the coreid bug,Colpula lativentris (Heteroptera: Coreidae)

Spatio-temporal variations of lifetime reproductive succes (LRS) of both male and female individuals of a coreid bugColpula lativentris were measured and analyzed using the multiple regression method of Arnold and Wade (1984a, b). The standardized variance of LRS was larger in males than that in females as males often to secure mates for a long period whereas females could easily find mates and oviposit simply dependent on ovarial maturation. LRS was partitioned into 4 consecutive fitness components: (1) reproductive lifespan, (2) copulating efficiency, (3) guarding efficiency (for males) or oviposition efficiency (for females), and (4) number of eggs per clutch. In males copulating efficiency was the largest determining factor of LRS, whereas in females reproductive lifespan was the most important factor. Such tendencies were stable on both a yearly and local basis. Patterns of relative contribution of natural selection (reproductive lifespan and number of eggs per clutch) and sexual selection (copulating efficiency and guarding or oviposition efficiency) to LRS were clearly different between males and females. This sexual difference is, at least to some extent, thought to be brought about by sexual selection among males for mating opportunity, though no physical fight was observed among males. Directional selection on body length was found only in relation to the clutch size of females because large females tended to lay larger clutches. No significant directional selection was found in other fitness components.     

THE EFFECT OF MATERNAL AGE AND REPRODUCTIVE HISTORY ON OFFSPRING SURVIVAL AND LIFETIME REPRODUCTION IN PREINDUSTRIAL HUMANS

Senescence is one of the least understood aspects of organism life history. In part, this stems from the relatively late advent of complete individual‐level datasets and appropriate statistical tools. In addition, selection against senescence should depend on the contribution to population growth arising from physiological investment in offspring at given ages, but offspring are rarely tracked over their entire lives. Here, we use a multigenerational dataset of preindustrial (1732–1860) Finns to describe the association of maternal age at offspring birth with offspring survival and lifetime reproduction. We then conduct longitudinal analyses to understand the drivers of this association. At the population level, offspring lifetime reproductive success (LRS) declined by 22% and individual λ, which falls with delays to reproduction, declined by 45% as maternal age at offspring birth increased from 16 to 50 years. These results were mediated by within‐mother declines in offspring survival and lifetime reproduction. We also found evidence for modifying effects of offspring sex and maternal socioeconomic status. We suggest that our results emerge from the interaction of physiological with social drivers of offspring LRS, which further weakens selection on late‐age reproduction and potentially molds the rate of senescence in humans.     

Producing sons reduces lifetime reproductive success of subsequent offspring in pre-industrial Finns

Life-history theory states that reproductive events confer costs upon mothers. Many studies have shown that reproduction causes a decline in maternal condition, survival or success in subsequent reproductive events. However, little attention has been given to the prospect of reproductive costs being passed onto subsequent offspring, despite the fact that parental fitness is a function of the reproductive success of progeny. Here we use pedigree data from a pre-industrial human population to compare offspring life-history traits and lifetime reproductive success (LRS) according to the cost incurred by each individual's mother in the previous reproductive event. Because producing a son versus a daughter has been associated with greater maternal reproductive cost, we hypothesize that individuals born to mothers who previously produced sons will display compromised survival and/or LRS, when compared with those produced following daughters. Controlling for confounding factors such as socio-economic status and ecological conditions, we show that those offspring born after elder brothers have similar survival but lower LRS compared with those born after elder sisters. Our results demonstrate a maternal cost of reproduction manifested in reduced LRS of subsequent offspring. To our knowledge, this is the first time such a long-term intergenerational cost has been shown in a mammal species.     

Mating frequency and inclusive fitness in Drosophila melanogaster

In many species, increased mating frequency reduces maternal survival and reproduction. In order to understand the evolution of mating frequency, we need to determine the consequences of increased mating frequency for offspring. We conducted an experiment in Drosophila melanogaster in which we manipulated the mating frequency of mothers and examined the survival and fecundity of the mothers and their daughters. We found that mothers with the highest mating frequency had accelerated mortality and more rapid reproductive senescence. On average, they had 50% shorter lives and 30% lower lifetime reproductive success (LRS) than did mothers with the lowest mating frequency. However, mothers with the highest mating frequency produced daughters with 28% greater LRS. This finding implies that frequent mating stimulates cross-generational fitness trade-offs such that maternal fitness is reduced while offspring fitness is enhanced. We evaluate these results using a demographic metric of inclusive fitness. We show that the costs and benefits of mating frequency depend on the growth rate of the population. In an inclusive fitness context, there was no evidence that increased mating frequency results in fitness costs for mothers. These results indicate that cross-generational fitness trade-offs have an important role in sexual selection and life-history evolution.     

Skewed distributions of lifetime reproductive success: beyond mean and variance

Lifetime reproductive performance is quantified here by the LRS (lifetime reproductive success), the random number of offspring an individual produces over its lifetime. Many field studies find that distributions of LRS among individuals are non‐normal, zero‐inflated and highly skewed. These results beg the question, what is the distribution of LRS predicted by demographic models when the only source of randomness is demographic stochasticity? Here we present the first exact analysis of the probability distribution of LRS for species described by age + stage models; our analysis starts with estimated vital rates. We illustrate with three examples: the Hadza, human hunter‐foragers (age‐only), the evergreen tree Tsuga canadensis (stage‐only) and Roe deer, Capreolus capreolus (age + stage). For each we obtain the exact distribution of LRS, but also calculate and discuss the first three moments. Our results point to important questions about how such LRS distributions affect natural selection, and life history evolution.     

温度和培养体积对大型溞种群动态和两性生殖影响的研究

研究了5个培养体积(50、100、200、400、1000 mL)和2个温度(20℃、25℃)下大型溞(Daphnia magna Straus)种群动态和两性生殖的变化,结果表明:(1)在相同培养体积下,随温度升高,大型溞首次抱卵时间缩短、首次产幼涵时间提前.在相同温度下,大型涵首次抱卵体长随培养体积的增大而增大.20℃和25℃下,1000 mL组大型溞首次抱卵体长分别是(2.54±0.02)mm和(2.71±0.01)mm.(2)在一定时间内,大型溞种群数量快速增加.但在较小培养体积下大型溞种群增长明显受到抑制.20℃和25℃下1000 mL培养体积组最大种群数量是2152 ind./1000 mL和3085 ind./1000 mL,分别约为50 mL组的4倍和13倍.培养体积与大型溞最大种群数量间存在显著相关性(P<0.01,n=15).(3)所有种群实验组均产生雄体,且雄体数量随种群数量的增加而相应增加.20℃下1000 mL组产生的雄体数量明显高于其他培养体积组,最大比例可达36%,且第一次产幼溞即出现雄性.雄体数量与大型溞最大种群数量之间呈显著的相关性(20℃:P<0.01,n=15;25℃:P<0.05,n=15).(4)20℃和25℃下,1000 mL组大型涵累计产生卵鞍分别为814和359个,且均由母溞后代形成.而其他体积组仅产生少量卵鞍或不产卵鞍,且所产卵鞍均由培养时的母溞形成.20℃和25℃下1000 mL组所产卵鞍的空卵鞍率分别达61.18%和99.16%.实验期间,20℃、1000 mL组所产生的卵鞍中,含休眠卵的比例均在20%以上.     

Natural selection on age-specific fertilities in human females: comparison of individual-level fitness measures.

Lifetime reproductive success and timing of reproduction are key components of life-history evolution. To understand the evolution of reproductive schedules, it is important to use a measure of fitness that is sensitive both to reproductive quantity and reproductive timing. There is a contradiction between the theory, which mainly focuses on the rate measures of fitness (r and lambda), and empirical studies, which mainly use lifetime reproductive success (LRS), or some of its correlates, as a fitness measure. We measured phenotypic selection on age-specific fertilities in three pre-modern human populations using individually estimated finite rate of increase, er (lambda). We found that lambda and lifetime reproductive success ranked individuals differently according to their fitness: for example, a female giving birth to four children at a young age may actually have a higher fitness than a female giving birth to six children at a greater age. Increase in fertility at the young age classes (15-19 years) was favoured by selection, but the intensity of selection on fertility was higher in the older age classes (20-30 years), where the variance in fertility was highest. Hence, variation in fertility in the older age classes (20-30) was actually responsible for most of the observed variation in fitness among the individuals. Additionally, more than 90% of variation in fitness (lambda) was attributable to individual differences in LRS, whereas only about 5% of all variation in fitness was due to differences in the reproductive schedule. The rate-sensitive fitness measure did not significantly challenge the importance of total fertility as a component of fitness in humans. However, the rate-sensitive measure clearly allowed more accurate estimation of individual fitness, which may be important for answering some more specific questions.     

Reproductive success of Macrotermes bellicosus (Isoptera, Macrotermitinae) in two neighbouring habitats

The fungus-cultivating, mound-building termite Macrotermes bellicosus can reach high densities in African savannah habitats, whereas in forests it is comparatively rare and is only found in relatively open areas. Earlier studies in the Comoé National Park (Côte d'Ivoire, West Africa) suggested that this might be because ambient temperatures are lower in the forest than the savannah. Therefore, forests seem to be suboptimal habitats. During 3 consecutive years we measured relevant fitness parameters in both habitats to test this hypothesis. Colonies in the savannah had higher reproductive outputs. They reproduced annually, producing high numbers of offspring (alates), whereas forest colonies reproduced on average only once every 3?years and even then only low numbers of alates were produced. Annual growth of mound height, which can be regarded as an indicator of colony growth, varied considerably between individual colonies and years. Nevertheless, in two years the growth rate of mounds in the shrub savannah was higher than that of mounds in the gallery forest. Unexpectedly, survival probability as calculated by Kaplan Meier analysis was much lower for colonies in the shrub savannah than for colonies in the gallery forest. Using these data in a computer simulation we calculated lifetime reproductive success (LRS) for an average colony in both habitats. As LRS was much higher for colonies in the shrub savannah than in the gallery forest, these results confirmed our suggestion that the forest is a suboptimal habitat for M. bellicosus.     

Lifetime fitness of short- and long-distance dispersing great reed warblers

Dispersal is of prime importance for many evolutionary processes and has been studied for decades. The reproductive consequences of dispersal have proven difficult to study, simply because it is difficult to keep track of dispersing individuals. In most previous studies evaluating the fitness effects of dispersal, immigrants at a study locality have been lumped into one category and compared to philopatric individuals. This is unfortunate, because there are reasons to believe that immigrants with long and short dispersal distances may differ substantially in reproductive success. In the present study, we used a combination of capture-recapturing and multilocus microsatellite genotyping to categorize great reed warblers at our Swedish study site as philopatric individuals or short- or long-distance dispersing immigrants. We then performed novel comparisons of lifetime reproductive success (LRS) and survival rates of these three dispersal categories. The birds belonged to cohorts 1987-1996, and data for their LRS were gathered between 1988 and 2003. The analyses showed that philopatric males attracted more females, produced more fledglings and recruits throughout their lives, and survived better than immigrants. Among the immigrant males, those categorized as long-distance dispersers had lowest LRS and survival probability. Models that included covariates of potential importance showed that the difference in LRS between dispersal categories was partly caused by corresponding variation in number of breeding years at our study site. These results indicate that short- and, in particular, long-distance dispersers were of poor phenotypic quality, but it may also be proposed that immigrants attracted few females because they were poorly adapted to the local social environment. In females, the number of local recruits corrected for the number of breeding years (as well as for number of fledglings) differed between dispersal categories in a pattern that suggests an intermediate optimal dispersal distance. Short-distance dispersers recruited more offspring per year (and per fledgling) than both philopatric individuals and long-distance dispersers. Data suggest that the low LRS of philopatric females was related to costs of inbreeding. The low LRS of long-distance dispersing females may have resulted from their offspring being especially prone to disperse outside the study area, but also other potential explanations exist, such as local maladaptation. Our study highlights the importance of separating immigrant birds on the basis of their genetic similarity to the local study population when analyzing variation in LRS and inferring realized gene flow.     

Correlates of lifetime reproductive success in three species of European ducks

Number of breeding attempts is a strong correlate of lifetime reproductive success (LRS) in birds, but the relative importance of potentially interacting factors affecting LRS has rarely been fully evaluated. We considered simultaneously five main factors hypothesized to influence LRS (age at first breeding, nesting date, number of breeding attempts, female traits, brood parasitism) by analyzing with path analysis 22-year data sets for 1,279 individually marked females and their offspring in tufted duck (Aythya fuligula), common pochard (A. ferina) and northern shoveler (Anas clypeata). We recaptured marked offspring as breeding adults (n=496 females) and obtained more complete estimates of LRS by incorporating information about banded ducklings of both sexes shot by hunters 12 months after banding (n=138). In tufted ducks and especially pochard (both diving duck species), late-hatched females tended to delay nesting until 2-years old. Most females (tufted duck, 74%; pochard, 71%; shoveler, 59%) apparently produced no breeding-age offspring. Number of breeding attempts (i.e., longevity) was the strongest correlate of LRS in all species, after controlling effects of age at first breeding, relative nest initiation date, wing length and body mass. Percentage of females producing recruits increased gradually with number of breeding attempts for all three species. Also, as expected, females nesting early in the breeding season had higher LRS than late-nesting individuals. In shoveler, female-specific characteristics of relatively longer wings and heavier late incubation body mass had positive effects on LRS, the latter feature being more common in 2-year-old nesters. In diving ducks, no relationships were detected between LRS and female-specific traits like wing length or body mass, and nor did acceptance of parasitic eggs have any deleterious impact on fitness estimates. Overall, number of fledged ducklings and LRS were related in tufted duck, weakly associated in pochard and unrelated in shoveler, implying that fledging success is not always a reliable measure of LRS.     

The relationship between habitat choice and lifetime reproductive success in female red deer

In non-territorial species, individuals can move freely and should be distributed in an ideal free manner between habitats and areas with respect to resources that influence lifetime reproductive success (LRS). Consequently, no relationship between diet quality and LRS should be expected. However, there have been no attempts to test this prediction. The present paper investigates the relationship between forage habitat use and LRS in red deer (Cervus elaphus) hinds within three neighbouring areas on the Isle of Rum which differed in their amounts of high-quality-forage habitat. Within areas, hinds move widely and have access to the same resources. We found no correlation between LRS of individual hinds and their use of high-quality-forage habitat (i.e. short Agrostis/Festuca grassland). Our analysis suggests that high hind densities on short Agrostis/Festuca grassland offset any advantages of increased access to preferred forage. These results support the hypothesis that red deer hinds are distributed in an ideal free manner with respect to the use of high-quality-forage habitat. However, hinds rarely leave areas where they are born, and the analysis suggests that constraints in changing areas hindered an ideal free distribution on a larger spatial scale. Consequently, mean LRS was not the same within the three investigated areas: one area, with a low amount of short Agrostis/Festuca grassland and a low hind density, contributed more male offspring (and more total offspring) per hind to the population than the other two areas. Received: 11 September 1998 / Accepted: 15 March 1999     

Male brood provisioning rates provide evidence for inter‐age competition for mates in female Cooper's Hawks Accipiter cooperii

Life history theory predicts that individuals should maximize lifetime reproductive success (LRS) by breeding as soon as they reach sexual maturity, yet many species delay breeding, either because there are insufficient available mates or breeding sites, or because delayed breeding yields higher LRS. Accipitriform species, such as Cooper's Hawk Accipiter cooperii, exhibit both delayed breeding and delayed plumage maturation. However, in certain circumstances, first‐year females in non‐definitive plumage do breed and apparently compete with older females for high‐quality breeding territories. We predicted that these young females are at a competitive disadvantage compared with older females and that older females would have both higher reproductive success and be able to acquire higher quality nesting territories. We conducted brood counts and measured prey delivery rates by male Cooper's Hawks in an expanding urban population located in Albuquerque, New Mexico (USA), to assess our prediction. We found that older females had higher reproductive success, fledging 1.6 more offspring than younger females, and that they occupied territories where males provisioned at higher rates of 0.37 more prey items per 2‐h period. Our results showed that older females fared better than first‐year females but it is unclear if this is the result of passive or active competition. Older females initiated nesting 14.3 days sooner than first‐year females and thus may have filled vacant, high‐quality territories before first‐year females began seeking mates. Additionally, first‐year females were never observed persistently to confront older females for breeding territories, but they did actively compete against each other. First‐year females may defer to older females who, in a direct competitive interaction, would be most likely to prevail. Thus, delayed plumage maturation in Cooper's Hawks may serve to focus competition for nesting territories within age classes.