Generation time and temporal scaling of bird population dynamics

Sæther, Bernt‐Erik; Lande, Russell; Engen, Steinar; Weimerskirch, Henri; Lillegård, Magnar; Altwegg, Res; Becker, Peter; Bregnballe, Thomas; Brommer, Jon E.; McCleery, Robin H.; Merilä, Juha; Nyholm, Erik; Rendell, Wallace B.; Robertson, Raleigh R.; Tryjanowski, Piotr; Visser, Marcel E.

doi:10.1038/nature03666

Cited by 179 publications

(170 citation statements)

References 24 publications

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“…Mammals with low mortality and low fecundity, such as seals, respond slowly to environmental variability, facilitating detection of density-dependent changes in population composition compared to animals with more rapid life cycles (Fowler 1981;Saether et al 2005). By adjusting recognized modeling techniques and theory (Gerrodette 1987;Caswell 2001;Sibly et al 2005) to empirically based simulations, this study shows that seal population structure as well as population growth rate are feasible parameters for detecting logistic growth using Gerrodette's (1987) polynomial.…”

Section: Discussionmentioning

confidence: 90%

Detecting Density Dependence in Recovering Seal Populations

Svensson

Eriksson

Härkönen

et al. 2010

AMBIO

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Time series of abundance estimates are commonly used for analyses of population trends and possible shifts in growth rate. We investigate if trends in age composition can be used as an alternative to abundance estimates for detection of decelerated population growth. Both methods were tested under two forms of density dependence and different levels of environmental variation in simulated time series of growth in Baltic gray seals. Under logistic growth, decelerating growth could be statistically confirmed after 16 years based on population counts and 14 years based on age composition. When density dependence sets in first at larger population sizes, the age composition method performed dramatically better than population counts, and a decline could be detected after 4 years (versus 10 years). Consequently, age composition analysis provides a complementary method to detect density dependence, particularly in populations where density dependence sets in late.

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Section: Discussionmentioning

confidence: 90%

Detecting Density Dependence in Recovering Seal Populations

Svensson

Eriksson

Härkönen

et al. 2010

AMBIO

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“…The relatively broad periods defined as pre- (1963-1989) and post-depletion (1990-2010) and pre-management for the purposes of this study spanned the intensification, peak, and decline of the U.S. Atlantic coastal shark fishery and may have masked changes that occurred within those years; unfortunately, sample size constraints prevented us from splitting the data into smaller intervals. However, the long life span and generation time of the species would likely dampen the magnitude of any such short-term changes occurring within that period; multi-generational timescales may be required to detect density-related trends (Saether et al 2005;Taylor and Gallucci 2009). It is also important to note that environmental changes may also play a confounding role in discerning density-mediated changes (Rose et al 2001); teasing apart the contribution of large-scale environmental and density-dependent effects to observed trends is an important and complicated area of future research (Taylor and Gallucci 2009).…”

Section: Discussionmentioning

confidence: 99%

Validated age and growth estimates for Carcharhinus obscurus in the northwestern Atlantic Ocean, with pre- and post management growth comparisons

Natanson

Gervelis

Winton³

et al. 2013

Environ Biol Fish

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Age and growth estimates for the dusky shark, Carcharhinus obscurus, were derived from vertebral centra collected in the northwestern Atlantic Ocean. Sample collection spanned the years prior to and following the implementation of management measures . Growth was compared pre-and post-population depletion and pre-and post-management to investigate the possibility of density-mediated shifts in age and growth parameters over time. There was no evidence of difference between periods for either sex. Additionally, bomb radiocarbon dating was used to determine the periodicity of band pair formation. Results support the traditional interpretation of annual band pairs up to approximately 11 years of age. After this time, vertebral counts considerably underestimate true age. Maximum validated ages were estimated to be between 38 and 42 years of age (an increase of 15 to 19 years over the band count estimates), confirming longevity to at least 42 years of age. Growth curves estimated using only validated data were compared to those generated using band pair counts. Logistic growth parameters derived from validated vertebral length-at-age data were L ∞ = 261.5 cm FL, L o =85.5 cm, t o =4.89 year and g= 0.15 year −1 for the sexes combined. Revised estimates of age at maturity were 17.4 years for males and 17.6 years for females.

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“…We estimated generation times (T ) for the species examined in the same manner as Saether et al [38]:…”

Section: Methodsmentioning

confidence: 99%

Contemporary morphological diversification of passerine birds introduced to the Hawaiian archipelago

Mathys

Lockwood

2011

Proc. R. Soc. B.

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Species that have been introduced to islands experience novel and strong selection pressures after establishment. There is evidence that exotic species diverge from their native source populations; further, a few studies have demonstrated adaptive divergence across multiple exotic populations of a single species. Exotic birds provide a good study system, as they have been introduced to many locations worldwide, and we often know details concerning the propagule origin, time of introduction, and dynamics of establishment and dispersal within the introduced range. These data make them especially conducive to the examination of contemporary evolution. Island faunas have received intense scrutiny, therefore we have expectations concerning the patterns of diversification for exotic species. We examine six passerine bird species that were introduced to the Hawaiian archipelago less than 150 years ago. We find that five of these show morphological divergence among islands from the time since they were established. We demonstrate that some of this divergence cannot be accounted for by genetic drift, and therefore we must consider adaptive evolution to explain it. We also evaluate evolutionary divergence rates and find that these species are diverging at similar rates to those found in published studies of contemporary evolution in native species.

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Generation time and temporal scaling of bird population dynamics

Cited by 179 publications

References 24 publications

Detecting Density Dependence in Recovering Seal Populations

Detecting Density Dependence in Recovering Seal Populations

Validated age and growth estimates for Carcharhinus obscurus in the northwestern Atlantic Ocean, with pre- and post management growth comparisons

Contemporary morphological diversification of passerine birds introduced to the Hawaiian archipelago

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