Patterns and ecological predictors of age-related performance in female North American barn swallows, Hirundo rustica erythrogaster (original) (raw)
Related papers
Journal of Animal Ecology, 2001
1We describe age-related reproductive performance and recapture rates of tree swallows (Tachycineta bicolor Vieillot) based on a 25-year study of a nestbox population in south-eastern Ontario, Canada (1975–99).2Performance improved from first-time breeders to intermediate-aged birds. Nest initiation advanced, and clutch size increased in both sexes. In females the number of hatchlings and fledglings increased, and the proportion of nests failing completely declined. Performance declined in females after ‘middle-age’, in the number of young fledged, and the proportion of young fledged relative to initial clutch and brood size. Also, the proportion of nests that failed completely increased in the oldest birds. Males showed similar patterns.3An index of performance incorporating clutch size, hatching and fledging efficiency, and two measures of total nest failure increased to, then declined after, 4 years of age in females and 3 years in males. The relationship between this index and age was best predicted by quadratic regression.4We found no support for three of four hypotheses to explain improvement in performance with age. Recapture rates declined after age 4Y in males, but remained unchanged in females until age 7Y +, while output decreased in both sexes (Residual Reproductive Value). Birds breeding repeatedly did not perform better during their first attempt compared to birds that bred only once (Selection). Birds with varied breeding experience did not differ in their performance within age-groups (Breeding Experience). We did find support for the Breeding Age hypothesis; in females with no breeding experience, there was a successive advance in laying and increase in clutch size from 2 to 4 years of age.5Improved performance may be due to skills acquired with age, such as those devoted to feeding and balancing energy demands, which are necessary to prepare and maintain individual condition prior to, and during, breeding. Senescence in performance after ‘middle-age’ may result from accumulated costs of previous breeding effort which have been identified in this species based on research elsewhere.We describe age-related reproductive performance and recapture rates of tree swallows (Tachycineta bicolor Vieillot) based on a 25-year study of a nestbox population in south-eastern Ontario, Canada (1975–99).Performance improved from first-time breeders to intermediate-aged birds. Nest initiation advanced, and clutch size increased in both sexes. In females the number of hatchlings and fledglings increased, and the proportion of nests failing completely declined. Performance declined in females after ‘middle-age’, in the number of young fledged, and the proportion of young fledged relative to initial clutch and brood size. Also, the proportion of nests that failed completely increased in the oldest birds. Males showed similar patterns.An index of performance incorporating clutch size, hatching and fledging efficiency, and two measures of total nest failure increased to, then declined after, 4 years of age in females and 3 years in males. The relationship between this index and age was best predicted by quadratic regression.We found no support for three of four hypotheses to explain improvement in performance with age. Recapture rates declined after age 4Y in males, but remained unchanged in females until age 7Y +, while output decreased in both sexes (Residual Reproductive Value). Birds breeding repeatedly did not perform better during their first attempt compared to birds that bred only once (Selection). Birds with varied breeding experience did not differ in their performance within age-groups (Breeding Experience). We did find support for the Breeding Age hypothesis; in females with no breeding experience, there was a successive advance in laying and increase in clutch size from 2 to 4 years of age.Improved performance may be due to skills acquired with age, such as those devoted to feeding and balancing energy demands, which are necessary to prepare and maintain individual condition prior to, and during, breeding. Senescence in performance after ‘middle-age’ may result from accumulated costs of previous breeding effort which have been identified in this species based on research elsewhere.
Behavioral Ecology and Sociobiology, 2011
When males become more ornamented and reproduce more successfully as they grow older, phenotypic correlations between ornament exaggeration and reproductive success can be confounded with age effects in crosssectional studies, and thus say relatively little about sexual selection on these traits. This is exemplified here in a correlative study of male fertilization success in a large colony of American barn swallows (Hirundo rustica erythrogaster). Previous studies of this species have indicated that two sexually dimorphic traits, tail length and ventral plumage coloration, are positively correlated with male fertilization success, and a mechanism of sexual selection by female choice has been invoked. However, these studies did not control for potential age-related variation in trait expression. Here, we show that male fertilization success was positively correlated with male tail length but not with plumage coloration. We also show that 1-year-old males had shorter tails and lower fertilization success than older males. This age effect accounted for much of the covariance between tail length and fertilization success. Still, there was a positive relationship between tail length and fertilization success among older males. But as this group consisted of males from different age classes, an age effect may be hidden in this relationship as well. Our data also revealed a longitudinal increase in both tail length and fertilization success for individual males. We argue that age-dependent ornament expression and reproductive performance in males complicate inferences about female preferences and sexual selection.
Journal of animal …, 2007
We investigated age-related changes in two reproductive traits (laying date and annual fecundity) in barn swallows Hirundo rustica L. using a mixed model approach to distinguish among between-and within-individual changes in breeding performance with age. 2. We tested predictions of age-related improvements of competence (i.e. constraint hypothesis) and age-related progressive disappearance of poor-quality breeders (i.e. selection hypothesis) to explain age-related increase in breeding performance in early life. 3. Reproductive success increased in early life, reaching a plateau at middle age (e.g. at 3 years of age) and decreasing at older age ( > 4 years). Age-related changes in breeding success were due mainly to an effect of female age. 4. Age of both female and male affected timing of reproduction. Final linear mixed effect models (LME) for laying date included main and quadratic terms for female and male age, suggesting a deterioration in reproductive performance at older age for both males and females. 5. We found evidence supporting the constraints hypothesis that increases in competence within individuals, with ageing being the most probable cause of the observed increase in breeding performance with age in early life. Two mechanisms were implicated: (1) advance in male arrival date with age provided middle-aged males with better access to mates. Yearling males arrived later to the breeding grounds and therefore had limited access to high-quality mates. (2) Breeding pairs maintaining bonds for 2 consecutive years (experienced pairs) had higher fecundity than newly formed inexperienced breeding pairs. 6. There was no support for the selection hypothesis because breeding performance was not correlated with life span. 7. We found a within-individual deterioration in breeding and migratory performance (arrival date) in the oldest age-classes consistent with senescence in these reproductive and migratory traits.
Symposium: Age-related reproductive performance in birds — The biological mechanisms
Journal of Ornithology, 1994
Among birds, many studies have shown that the reproductive performance of individuals increases with advancing age (1); effects of senescence have been demonstrated less frequently. To date, most work has dwelled principally on the evolution and maintenance of ontogenetic processes (2). Relatively little attention has been focused on the underlying ecological, physiological and social mechanisms responsible for the widespread pattern of age-specific reproduction in birds. With behaviour and energetics studies, and monitoring success of known-age individuals throughout their lives one can begin elucidating some of the mechanisms involved. Biological mechanisms may act directly on age classes to influence fitness of individuals, or indirectly by interactions with ecological or environmental factors. When age-specific variation occurs at an early life history stage (e. g., spring body condition), age-specific effects may cascade through the breeding effort and profoundly influence an individuai's fitness. Little is known about factors responsible for senescence. In this symposium, 5 types of biological mechanisms are examined. Foraging ability and/or efficiency and physiological efficiency (converting nutrients to eggs or energetic cost of parental duties) may improve with age, resulting in improved breeding success. The ability to acquire high quality nest sites may also improve with age and/or experience (2). Young birds may perform poorly because they are less able to compete with older neighbours (social dominance) for high quality nesting or foraging sites. Parental competence, such as &fenc e of young may improve with age, perhaps because older parents are more knowledgeable in choosing good brood rearing sites, more vigilant for predators, or more competent at defending offspring from predators. Within species, age-specific effects may occur at some life history stages and be absent in others (2, 3). The pattern or strength of age-specific effects for a trait like clutch size, may vary with habitat type, environmental extreme (3) or landscape degradation. Thus, biological mechanisms that cause age-specific performance may explain a substantial amount of the variation in reproductive success of birds observed annually or among populations. Future work should develop general relationships such as whether age-specific patterns are related to life history patterns such as foraging mode, longevity or taxon. Several studies have shown that age-specific effects involve both proximate and ultimate factors (2, 4). Experiments need to be done across age classes that discriminate between proximate (constraint) and ultimate (restraint) mechanisms.
Differences in Reproductive Success in Young and Old Females of a Long-Lived Species
Animals
Long-lived species are particularly interesting for investigation of trade-offs that shape reproductive allocation and the effective contribution to the next generations. Life history theory predicts that these species will buffer environmental stochasticity via changes in the reproductive investment, while maintaining high adult survival rates. The spur-thighed tortoise was selected as a case study in order to investigate the relationship between the linked maternal characteristics (size and age) and related traits in their hatchlings. We tracked naturally emerging hatchlings from young and old females under semi-natural conditions to test variations in hatchling numbers, body mass, size and survival over two years. We used linear mixed-effect models to analyze variations in hatchling body mass and size, and a mark–release–recapture framework to model their survival. Our study illustrates that old females of long-lived species have greater offspring numbers, greater survival and sm...
Age-dependent terminal declines in reproductive output in a wild bird
PloS one, 2012
In many iteroparous species individual fitness components, such as reproductive output, first increase with age and then decline during late-life. However, individuals differ greatly in reproductive lifespan, but reproductive declines may only occur in the period just before their death as a result of an age-independent decline in physiological condition. To fully understand reproductive senescence it is important to investigate to what extent declines in late-life reproduction can be explained by age, time until death, or both. However, the study of late-life fitness performance in natural populations is challenging as the exact birth and death dates of individuals are often not known, and most individuals succumb to extrinsic mortality before reaching old age. Here, we used an exceptional long-term longitudinal dataset of individuals from a natural, closed, and predator-free population of the Seychelles warbler (Acrocephalus sechellensis) to investigate reproductive output, both i...
Patterns and Mechanisms for Age-dependent Reproduction and Survival in Birds
Integrative and Comparative Biology, 1995
SYNOPSIS. The majority of bird species exhibit age-dependent survival and reproduction. In almost all cases, first time breeders or young individuals perform at a lower and slower rate than older individuals. This review highlights the importance of age-dependent effects and urges further study of the proximate and ultimate mechanisms involved. Age effects show substantive variation across life history stage, breeding season, year, cohort, habitat types and environmental conditions both within and across taxons. In some populations or years, age effects disappear. Despite the variable patterns, age effects show amazing persistence in a variety of extreme ecological and environmental conditions. Experimental manipulations of food, predation pressure and breeding experience do not usually remove age effects. Age-dependent effects may be maintained or accumulate through the breeding season and profoundly influence fitness, or they may be washed out or reversed by events later in the breeding season. Recently, we have amassed substantive information about the patterns of variation in age-dependent reproduction and survival among individuals, but we have made little progress toward understanding the proximate mechanisms responsible for this variation. Proximate and ultimate processes are inextricably linked, and thus the study of age-dependence is highly relevant to the further development of life history theory. Studies of age-dependent performance have general relevance to population management and conservation issues as age sub-structuring may contribute substantially to annual or inter-populational variation in reproductive success.
Ecology, 2014
We used a long-term data set (26 years) from Audouin's Gull (Larus audouinii ), a long-lived seabird, to address the relationship between the age-dependent pattern of reproductive performance and environmental conditions during breeding. Although theoretical models predict that the youngest and oldest breeders (due to inexperience and senescence, respectively) will perform less well than intermediate age classes, few empirical data exist regarding how this expected pattern varies with food availability. To assess the influence of age and food availability (corrected by population size of the main consumers to take into account density dependence) on a number of breeding parameters (laying dates, egg volume, clutch size, and hatching success), we modeled mean and variances of these parameters by incorporating heterogeneity into generalized linear models. All parameters varied with age and to different degrees, depending on food availability. As expected, performance improved with increased food supply, and the observed age pattern was quadratic, with poorer breeding performances occurring in extreme ages. For most parameters (except for laying dates, for which age and food did not interact), the pattern changed with food somewhat unexpectedly; the differences in performance between age classes were higher (i.e., the quadratic pattern was more noticeable) when food was more readily available than when food availability was lower. We suggest that, under poor environmental conditions, only high-quality individuals of the younger and older birds bred and that the differences in breeding performance between age classes were smaller. Although variances for egg volume were constant, variances for laying dates were highest for the youngest breeders and tended to decrease with age, either due to the selection of higher-quality individuals or to a greater frequency of birds skipping breeding with age, especially when food was in low supply. Our results show that mean and variances of breeding parameters changed with age, but that this pattern was different for each parameter and also varied according to food availability. It is likely that, other than food, certain additional factors (e.g., sex, cohort effects, density dependence) also influence changes in breeding performance with age, and this may preclude the finding of a common pattern among traits and among studies on different taxa.