scholarly journals Demographic drivers of decline and recovery in an Afro-Palaearctic migratory bird population

2016 ◽  
Vol 283 (1842) ◽  
pp. 20161387 ◽  
Author(s):  
Catriona A. Morrison ◽  
Robert A. Robinson ◽  
Simon J. Butler ◽  
Jacquie A. Clark ◽  
Jennifer A. Gill
Keyword(s):  
Population Growth ◽  
Survival Rates ◽  
Bird Species ◽  
Migratory Bird ◽  
Adult Survival ◽  
High Survival ◽  
Population Declines ◽  
High Productivity ◽  
Population Growth Rates ◽  
Sub Saharan

Across Europe, rapid population declines are ongoing in many Afro-Palaearctic migratory bird species, but the development of appropriate conservation actions across such large migratory ranges is severely constrained by lack of understanding of the demographic drivers of these declines. By constructing regional integrated population models (IPMs) for one of the suite of migratory species that is declining in the southeast of Britain but increasing in the northwest, we show that, while annual population growth rates in both regions vary with adult survival, the divergent regional trajectories are primarily a consequence of differences in productivity. Between 1994 and 2012, annual survival and productivity rates ranged over similar levels in both regions, but high productivity rates were rarer in the declining southeast population and never coincided with high survival rates. By contrast, population growth in the northwest was fuelled by several years in which higher productivity coincided with high survival rates. Simulated population trajectories suggest that realistic improvements in productivity could have reversed the decline (i.e. recovery of the population index to more than or equal to 1) in the southeast. Consequently, actions to improve productivity on European breeding grounds are likely to be a more fruitful and achievable means of reversing migrant declines than actions to improve survival on breeding, passage or sub-Saharan wintering grounds.

Life in the Slow Lane: Ecology and Conservation of Long-Lived Marine Animals

1999 ◽  
Keyword(s):  
Life History ◽  
Population Growth ◽  
Growth Rates ◽  
Anthropogenic Impacts ◽  
Survival Rates ◽  
Conservation Strategies ◽  
Adult Survival ◽  
Population Growth Rates ◽  
Important Prey ◽  
The Status

<em>Abstract.</em> —Seabirds become mature at a late age, experience low annual fecundity, often refrain from breeding, and enjoy annual adult survival rates as high as 98%. This suite of life history characteristics limits the capacity for seabird populations to recover quickly from major perturbations, and presents important conservation challenges. Concern over anthropogenic impacts on seabird populations has led to the initiation of long-term field programs to monitor seabird reproductive performance and population dynamics. In addition, seabirds have been recognized as potentially useful and economical indicators of the state of the marine environment and, in particular, the status of commercially important prey stocks. This paper reviews demographic and life history attributes of seabird populations and uses this information to explore the consequences of longevity from the respective standpoints of conservation and monitoring goals. Analysis of a simplified life cycle model reveals that maximum potential population growth rates (λ) under ideal circumstances fall within the range of 1.03–1.12 for most species, though growth rates realized in nature will always be lower. Elasticity analysis confirms that seabird population growth rates are extremely sensitive to small variations in adult survival rates, and dictates that survival monitoring should be considered an essential component of conservation strategies. As in other organisms with long life spans, ecological and physiological costs of reproduction are expected to figure prominently in seabird reproductive decisions. Consequently, understanding how seabirds allocate reproductive effort in response to varying environmental conditions is an important prerequisite for correctly interpreting field data from monitoring studies.

scholarly journals Hunting of migratory birds in North Sinai, Egypt

2015 ◽  
Vol 26 (1) ◽  
pp. 39-51 ◽  
Author(s):  
PERRI EASON ◽  
BASEM RABIA ◽  
OMAR ATTUM
Keyword(s):  
Migratory Birds ◽  
Bird Species ◽  
Migratory Bird ◽  
Mediterranean Coast ◽  
Population Declines ◽  
Mp3 Players ◽  
Southern Mediterranean ◽  
Sand Bar ◽  
North Sinai ◽  
Desert Scrub

SummaryDuring autumn migration, people set trammel nets along most of the Mediterranean coast of Egypt, with migrating Common Quail Coturnix coturnix as their primary target. These nets capture large numbers of quail, but also illegally capture other birds, which are then killed. We present the results of surveys from 2008 to 2012 along these lines of nets on the coast of North Sinai, Egypt. In desert scrub, which covers most of the Sinai coast, the mean number of quail killed reached a high of 357.1 per km per day in 2012, with a grand mean over the study period of 191.9 per km per day. Trammel nets also captured 54 other bird species in 28 families. Species captured at the highest rates in desert scrub included Corncrake Crex crex, Isabelline Wheatear Oenanthe isabellina and Greater Short-toed Lark Calandrella brachydactyla. Based on mean rates of capture from 2008 to 2012 in desert scrub and sand bar habitats, we estimate 2.0 million quail and 0.5 million birds of other species are killed annually in North Sinai during the 45 days of peak migration. In 2012, however, after the use of MP3 players to attract quail became widespread, we estimate that 3.3 million quail and 0.5 million other birds were captured. Hunters near the coast have recently begun covering shrubs and trees with mist nets to catch passerines. From 2010 to 2012, mist nets along our survey routes caught birds of 17 species in three families, with seven of these species caught only in this type of net. Hunting is likely to be a contributing factor to population declines for some species that migrate across Egypt and further studies of migratory bird hunting along the southern Mediterranean shore are badly needed.

scholarly journals Fitness of breeders in social Damaraland mole-rats is independent of group size

2021 ◽  
Author(s):  
Jack Thorley ◽  
Hanna Bensch ◽  
Kyle Finn ◽  
Tim Clutton-Brock ◽  
Markus Zöttl
Keyword(s):  
Reproductive Success ◽  
Group Size ◽  
Survival Rates ◽  
Group Living ◽  
Adult Survival ◽  
High Survival ◽  
Successful Reproduction ◽  
Related Group ◽  
Group Members ◽  
Using Data

Damaraland mole-rats (Fukomys damarensis) are usually viewed as an obligatorily group living eusocial species in which successful reproduction is dependent on reproductive altruism of closely related group members. However, the reproductive ecology of social mole-rats in their natural environment remains poorly understood and it is unclear to what extent successful reproduction is dependent on assistance from other group members. Using data from a 7-year field study of marked individuals, we show that, after dispersal from their natal group, individuals typically settled alone in new burrow systems where they enjoyed high survival rates, and often remained in good body condition for several years before finding a mate. Unlike most other eusocial or singular cooperative breeders, we found that Damaraland mole-rats reproduced successfully in pairs without helpers and experimentally formed pairs had the same reproductive success as larger established groups. Overall there was only a weak increase in reproductive success with increasing group size and no effect of group size on adult survival rates across the population. Juveniles in large groups grew faster early in life but their growth rates declined subsequently so that they eventually plateaued at a lower maximum body mass than juveniles from small groups. Taken together, our data suggest that the fitness benefits of group living to breeders are small and we suggest that extended philopatry in Damaraland mole-rats has evolved because of the high costs and constraints of dispersal rather than because of strong indirect benefits accrued through cooperative behaviour.

scholarly journals Range expansion is associated with increased survival and fecundity in a long-lived bat species

2019 ◽  
Vol 286 (1906) ◽  
pp. 20190384 ◽  
Author(s):  
P.-L. Jan ◽  
L. Lehnen ◽  
A.-L. Besnard ◽  
G. Kerth ◽  
M. Biedermann ◽  
...  
Keyword(s):  
Life History ◽  
Population Growth ◽  
Range Expansion ◽  
Empirical Studies ◽  
Simulated Data ◽  
Adult Survival ◽  
Juvenile Survival ◽  
Average Growth ◽  
Population Growth Rates ◽  
Expanding Population

The speed and dynamics of range expansions shape species distributions and community composition. Despite the critical impact of population growth rates for range expansion, they are neglected in existing empirical studies, which focus on the investigation of selected life-history traits. Here, we present an approach based on non-invasive genetic capture–mark–recapture data for the estimation of adult survival, fecundity and juvenile survival, which determine population growth. We demonstrate the reliability of our method with simulated data, and use it to investigate life-history changes associated with range expansion in 35 colonies of the bat species Rhinolophus hipposideros . Comparing the demographic parameters inferred for 19 of those colonies which belong to an expanding population with those inferred for the remaining 16 colonies from a non-expanding population reveals that range expansion is associated with higher net reproduction. Juvenile survival was the main driver of the observed reproduction increase in this long-lived bat species with low per capita annual reproductive output. The higher average growth rate in the expanding population was not associated with a trade-off between increased reproduction and survival, suggesting that the observed increase in reproduction stems from a higher resource acquisition in the expanding population. Environmental conditions in the novel habitat hence seem to have an important influence on range expansion dynamics, and warrant further investigation for the management of range expansion in both native and invasive species.

Characterization of elasticity patterns of North American freshwater fishes

2006 ◽  
Vol 63 (9) ◽  
pp. 2050-2066 ◽  
Author(s):  
Luis A Vélez-Espino ◽  
Michael G Fox ◽  
Robert L McLaughlin
Keyword(s):  
Population Growth ◽  
North American ◽  
Growth Rates ◽  
Freshwater Fishes ◽  
Adult Survival ◽  
Juvenile Survival ◽  
Vital Rates ◽  
Population Growth Rates ◽  
North American Freshwater ◽  
Trade Offs

We applied elasticity analysis to 88 North American freshwater fishes to assess the relative impacts of changes in the vital rates on asymptotic population growth. Variance in vital rates was summarized for four distinct functional groups: (i) species with population growth rates strongly sensitive to perturbations in adult survival; (ii) species with population growth rates sensitive to perturbations in overall survival; (iii) species with population growth rates most sensitive to perturbations in juvenile survival; and (iv) species with population growth rates sensitive to perturbations in juvenile survival and fecundity. The results of the present study also showed that (a) elasticity patterns cannot be inferred in a straightforward manner from trade-offs between life-history traits, (b) the sensitivity of a population's growth rate to changes in adult survival and fecundity can be predicted empirically from life span and age at maturity, respectively, (c) elasticities are highly conserved among genera within the same taxonomic family, and (d) there are key divergences between elasticity patterns of freshwater fish and other vertebrate taxa.

scholarly journals Poor horse traders: large mammals trade survival for reproduction during the process of feralization

2009 ◽  
Vol 276 (1663) ◽  
pp. 1911-1919 ◽  
Author(s):  
Sophie Grange ◽  
Patrick Duncan ◽  
Jean-Michel Gaillard
Keyword(s):  
Population Growth ◽  
Reproductive Performance ◽  
High Density ◽  
Adult Survival ◽  
Demographic Parameters ◽  
Adult Males ◽  
High Fecundity ◽  
Population Growth Rates ◽  
Feral Animals ◽  
Feral Ungulates

We investigated density dependence on the demographic parameters of a population of Camargue horses ( Equus caballus ), individually monitored and unmanaged for eight years. We also analysed the contributions of individual demographic parameters to changes in the population growth rates. The decrease in resources caused a loss of body condition. Adult male survival was not affected, but the survival of foals and adult females decreased with increasing density. Prime-aged females maintained high reproductive performance at high density, and their survival decreased. The higher survival of adult males compared with females at high density presumably results from higher investment in reproduction by mares. The high fecundity in prime-aged females, even when at high density, may result from artificial selection for high reproductive performance, which is known to have occurred in all the major domestic ungulates. Other studies suggest that feral ungulates including cattle and sheep, as these horses, respond differently from wild ungulates to increases in density, by trading adult survival for reproduction. As a consequence, populations of feral animals should oscillate more strongly than their wild counterparts, since they should be both more invasive (as they breed faster), and more sensitive to harsh environmental conditions (as the population growth rate of long-lived species is consistently more sensitive to a given proportional change in adult survival than to the same change in any other vital rate). If this principle proves to be general, it has important implications for management of populations of feral ungulates.

Using population dynamics modelling to evaluate potential success of restoration: a case study of a Hawaiian vine in a changing climate

2014 ◽  
Vol 42 (1) ◽  
pp. 20-30 ◽  
Author(s):  
TAMARA M. WONG ◽  
TAMARA TICKTIN
Keyword(s):  
Population Growth ◽  
Growth Rates ◽  
Key Management ◽  
Demographic Data ◽  
Population Decline ◽  
Management Strategies ◽  
Survival Rates ◽  
Population Modelling ◽  
Population Growth Rates

SUMMARYDemographic comparisons between wild and restored populations of at-risk plant species can reveal key management strategies for effective conservation, but few such studies exist. This paper evaluates the potential restoration success ofAlyxia stellata, a Hawaiian vine. Stage-structured matrix projection models that compared long-term and transient dynamics of wild versus restoredA. stellatapopulations, and restored populations under different levels of canopy cover, were built from demographic data collected over a four year period. Stochastic models of wild populations projected stable or slightly declining long-term growth rates depending on frequency of dry years. Projected long-term population growth rates of restored populations were significantly higher in closed than open canopy conditions, but indicated population decline under both conditions. Life table response experiments illustrated that lower survival rates, especially of small adults and juveniles, contributed to diminished population growth rates in restored populations. Transient analyses for restored populations projected short-term decline occurring even faster than predicted by asymptotic dynamics. Restored populations will not be viable over the long term under conditions commonly found in restoration projects and interventions will likely be necessary. This study illustrates how the combination of long-term population modelling and transient analyses can be effective in providing relevant information for plant demographers and restoration practitioners to promote self-sustaining native populations, including under future climates.

scholarly journals Evidence for the buffer effect operating in multiple species at a national scale

2015 ◽  
Vol 11 (1) ◽  
pp. 20140930 ◽  
Author(s):  
Martin J. P. Sullivan ◽  
Stuart E. Newson ◽  
James W. Pearce-Higgins
Keyword(s):  
Population Growth ◽  
Population Change ◽  
Spatial Scales ◽  
Bird Species ◽  
Buffer Effect ◽  
Breeding Bird ◽  
Population Growth Rates ◽  
National Monitoring ◽  
Multiple Species ◽  
The Uk

A long-standing aim of ecologists is to understand the processes involved in regulating populations. One such mechanism is the buffer effect, where lower quality habitats are increasingly used as a species reaches higher population densities, with a resultant average reduction in fecundity and survival limiting population growth. Although the buffer effect has been demonstrated in populations of a number of species, a test of its importance in influencing population growth rates of multiple species across large spatial scales is lacking. Here, we use habitat-specific population trends for 85 bird species from long-term national monitoring data (the UK Breeding Bird Survey) to examine its generality. We find that both patterns of population change and changes in habitat preference are consistent with the predictions of the buffer effect, providing support for its widespread operation.

Malthus and the Theory of ‘Unequal Powers’: Population and Food Production in India, 1800–1947

1986 ◽  
Vol 20 (4) ◽  
pp. 661-701 ◽  
Author(s):  
Simon Commander
Keyword(s):  
Population Growth ◽  
Food Production ◽  
Climatic Factors ◽  
Green Revolution ◽  
Sub Saharan Africa ◽  
Population Growth Rates ◽  
Indian Agriculture ◽  
Sub Saharan ◽  
Food Imports ◽  
Food Commodities

The spectre of a ‘Malthusian’ catastrophe engulfing the subcontinent commands less attention currently than in relatively recent times. This is largely attributable to the greater sense of confidence in the food-grain supply capacity of Indian agriculture in the wake of the Green Revolution. From the mid-1960s through to 1980, output has maintained a growth rate in excess of 2.5% p.a., with yield increments rather than area increments accounting for the major part. Since 1950, per capita net availability of foodgrains has increased by over 20%, while the real price of foodgrains has shown a steady downward trend since 1968. Current projections suggest that self-sufficiency in food production can be sustained through to the end of the century. Yet this remains partly contingent on climatic factors and a slackening trend of population growth. However, population growth rates currently exceed 2.2% p.a. and the relative stability of fertility rates means that a diminution is by no means assured. While supply shortfalls could be met through increased imports of food commodities, the possible emergence of India in the longer term as a food deficitary economy could have serious implications for the international grain market, given the current structure of supply for foodgrains and the growing dependence, particularly in Sub-Saharan Africa, on food imports.

scholarly journals Ecological Genetics of the Wild Rabbit in Australia. III. Comparison of the Microgeographical Distribution of Alleles in Two Different Environments

1980 ◽  
Vol 33 (3) ◽  
pp. 385 ◽  
Author(s):  
BJ Richardson
Keyword(s):  
Adenosine Deaminase ◽  
Survival Rates ◽  
Ecological Genetics ◽  
High Survival ◽  
Wild Rabbit ◽  
Gene Frequencies ◽  
High Productivity ◽  
Phosphogluconate Dehydrogenase ◽  
Carboxylesterase 1 ◽  
Pattern Of Variation

The differences in distribution of gene frequencies at three polymorphic loci (adenosine deaminase, carboxylesterase-1 and phosphogluconate dehydrogenase) were determined for rabbit populations living in two markedly different environments. One, a highland population from Snowy Plains N.S.W., has low productivity and high survival rates, and the second, a dry plains population from Urana, N.S.W., has high productivity and low survival rates. The amount of sub population differentiation at each locus was distinctive, and was different in the two environments with significant differentiation occurring for phosphogluconate dehydrogenase at both areas, for carboxylesterase-1 at Snowy Plains and for adenosine deaminase at Urana. The general significance of these results was demonstrated by determining the distribution of the variation in a third population. This population was subject to the same historical climatic events as the Urana population and showed a similar pattern of variation. Various explanations of the data are considered and a combination of chance and selection, rather than either alone, seems to offer the most satisfactory explanation. The demographic differences between the populations seemed to play no part in explaining the patterns observed.

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