JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecology. Abstract. We examined the effect of age on breeding performance in male and female Merlins (Falco columbarius) from a natural population using a long-term data set. In the analysis, we examined whether differences in chick hatch date and brood size associated with parents of different ages arose due to selection of superior individuals (differential mortality hypothesis) or to changes within individuals over time (inadequate experience hypothesis). In addition, we examined the effect of longevity on production of recruits and lifetime reproductive success (LRS). In both sexes, breeding performance improved with age. In females, this was mainly the result of disproportionate mortality of inferior breeders, with less evidence to support performance changes within individuals. Among males, changes in breeding performance with age were largely the result of improvements within individuals early in their life (between age 1 and 2 +). Production of recruits was not dependent on parental age at the time of breeding for either sex. Recruit production and LRS were both influenced by longevity, so that longer-lived birds produced more offspring over their lifetimes and thereby had a greater probability of producing recruits. The differences between the sexes in terms of age-dependent breeding performance are likely a consequence of the differing roles the two parents play in reproduction. Male Merlins provide most of the food for the pair and their young during the breeding season, and changes in hunting skill with age may account for individual improvements in breeding performance.

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We examined the effects of nest‐site quality and bird quality on breeding performance in male and female Merlins Falco columbarius from a long‐term study in Saskatoon, Saskatchewan. In addition, we tested whether nest‐site quality was associated with survival, as well as lifetime reproductive success (LRS). For females, nest‐site quality had little influence on any of the measures of breeding performance or survival. Even so, when females switched nest‐sites, they tended to move to better ones. Hatch date was repeatable for the same females occupying different nest‐sites but not for the same sites occupied by different females. Among males, birds surviving past each age category tended to occupy nest‐sites of higher quality, and LRS was positively correlated with nest‐site quality. The relationship between nest‐site quality and LRS was heavily influenced by the poorest nest‐sites. When males switched nest‐sites, they too tended to move to ones of higher quality. In addition, chick hatch date was repeatable neither for the same males occupying different sites nor for the same sites occupied by different males. As with most other raptors, male Merlins provide most of the food for the pair and their young during the breeding season, and differences in nest‐site quality may have affected the effort needed by males to secure food. Female Merlins, however, appear still to have considerable control over the timing of breeding.

Ixodes scapularis, a known vector of Borrelia burgdorferi sensu stricto (Bbss), is undergoing range expansion in many parts of Canada. The province of New Brunswick, which borders jurisdictions with established populations of I. scapularis, constitutes a range expansion zone for this species. To better understand the current and potential future distribution of this tick under climate change projections, this study applied occupancy modelling to distributional records of adult ticks that successfully overwintered, obtained through passive surveillance. This study indicates that I. scapularis occurs throughout the southern-most portion of the province, in close proximity to coastlines and major waterways. Milder winter conditions, as indicated by the number of degree days <0 °C, was determined to be a strong predictor of tick occurrence, as was, to a lesser degree, rising levels of annual precipitation, leading to a final model with a predictive accuracy of 0.845 (range: 0.828-0.893). Both RCP 4.5 and RCP 8.5 climate projections predict that a significant proportion of the province (roughly a quarter to a third) will be highly suitable for I. scapularis by the 2080s. Comparison with cases of canine infection show good spatial agreement with baseline model predictions, but the presence of canine Borrelia infections beyond the climate envelope, defined by the highest probabilities of tick occurrence, suggest the presence of Bbss-carrying ticks distributed by long-range dispersal events. This research demonstrates that predictive statistical modelling of multi-year surveillance information is an efficient way to identify areas where I. scapularis is most likely to occur, and can be used to guide subsequent active sampling efforts in order to better understand fine scale species distributional patterns.

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Accurate estimation of survival probabilities is an important component of population demographics, and it permits a test of the life-history prediction that densities influence population dynamics via suppression of survival rates. As part of a long-term study of urban-nesting Merlins (Falco columbarius), we estimated survival rates and tested for the effects of density dependence based on capture histories from 1,354 individuals (43 males and 110 females caught for the first time as adult breeding birds, and 597 males and 604 females caught for the first time as locally produced nestlings). Overall capture probabilities were 0.55 ± SD of 0.039 per year for adults, 0.10 ± 0.075 per year for juvenile males, and 0.58 ± 0.23 per year for juvenile females. Mean survival rate of adults was 0.62 ± 0.11 per year and did not differ significantly between males and females. Overall juvenile survival rates were 0.23 ± 0.032 for males and 0.055 ± 0.012 for females. Band returns suggest that the discrepancy in survival rates between juvenile males and females resulted from higher natal dispersal of females rather than from lower survival. Survival of adults (but not juveniles) was negatively density dependent, suggesting that density-dependent declines in survival exerted a regulatory effect on population size.

No abstract

We examined the effect of age on breeding performance in male and female Merlins (Falco columbarius) from a natural population using a long‐term data set. In the analysis, we examined whether differences in chick hatch date and brood size associated with parents of different ages arose due to selection of superior individuals (differential mortality hypothesis) or to changes within individuals over time (inadequate experience hypothesis). In addition, we examined the effect of longevity on production of recruits and lifetime reproductive success (LRS). In both sexes, breeding performance improved with age. In females, this was mainly the result of disproportionate mortality of inferior breeders, with less evidence to support performance changes within individuals. Among males, changes in breeding performance with age were largely the result of improvements within individuals early in their life (between age 1 and 2+). Production of recruits was not dependent on parental age at the time of breeding for either sex. Recruit production and LRS were both influenced by longevity, so that longer‐lived birds produced more offspring over their lifetimes and thereby had a greater probability of producing recruits. The differences between the sexes in terms of age‐dependent breeding performance are likely a consequence of the differing roles the two parents play in reproduction. Male Merlins provide most of the food for the pair and their young during the breeding season, and changes in hunting skill with age may account for individual improvements in breeding performance.