Annual Adult Survival Research Articles

Population dynamics of the black-cheeked gnateater (Conopophaga melanops, Conopophagidae) in southern Brazil

Abstract:Population structure and dynamics of the black-cheeked gnateater (Conopophaga melanops) were studied at Salto Morato Nature Reserve, in Paraná, southern Brazil, from October 2006 to September 2007. Territory size and population density, breeding season (timing and length), reproductive success and annual survival rates were estimated from sightings of 18 marked adult birds and the success of 18 nesting attempts. The black-cheeked gnateater is socially monogamous and territorial, with a breeding-season length of approximately 3 mo beginning in early October. Predation caused most nest failures, nest survival was 0.96 d−1and apparent annual nesting success was 22%, resulting in annual productivity of 0.36 individuals per adult. Apparent adult annual survival was ~0.44 y−1. Seventy-five per cent of fledglings survived at least 2 mo after fledging. Two methods of estimating population growth rate suggest very different rates: r = −0.04 (~ stable), or λ varies between 0.475–0.616 (declining). Yet, low apparent adult survival suggests that territories are not permanent, perhaps abandoned after nest failure. We find that by estimating population growth, even in short-term studies, testable hypotheses can be generated that will allow better understanding of population dynamics.

Separating Components of Variation in Survival of Mule Deer in Colorado

ABSTRACT Survival is an important parameter for understanding population dynamics of mule deer (Odocoileus hemionus) and other large herbivores. To understand long‐term dynamics it is important to separate sampling and biological process variation in survival. Moreover, knowledge of correlations in survival across space and between young and adults can provide more informed predictions of survival in unsampled areas. We estimated survival of fawn, yearling, and adult mule deer from 4 spatially separated regions of Colorado, USA, from 1997 to 2008. We also estimated process variance in survival across time for each age and site using Markov chain Monte Carlo (MCMC) methods. Finally, we estimated correlations in survival among sites and ages with MCMC methods. Average winter fawn survival was 0.721 (SD = 0.024) for the 4 regions. Average winter adult female survival was 0.935 (SD = 0.007). Annual adult female survival ranged from 0.803 (SD = 0.017) to 0.900 (SD = 0.028) for the 4 regions, excluding hunting mortality. The correlation between fawn and adult female survival was high, 0.563 (SD = 0.253). Correlations in winter fawn survival were higher between populations at the same latitude than they were for populations to the north and south. We used survival estimates from our analysis to inform prior distributions for a Bayesian population dynamics model from one population in Colorado and compared that model to one with noninformative prior distributions. Population models including informative prior distributions based on our results performed better than those noninformative prior distributions on survival, providing more biologically defensible results when data were sparse. Knowledge of process distributions of survival can help wildlife managers better predict future population status and understand the likely range of survival rates.

A Fledgling-mass Threshold Greatly Affects Juvenile Survival in the Hawaii Akepa (Loxops coccineus coccineus)

ABSTRACT. Offspring quality is an important issue in avian life-history theory, particularly with regard to birds that have low reproductive rates and extended parental care. Offspring mass has been identified as an indicator of quality in several bird species. These studies have shown that nestling mass is predictive of offspring survival outside the nest, but few studies have considered the role of fledgling mass. Mass during the fledgling period may change and influence juvenile survival. Fledgling mass may be especially relevant for tropical birds that have very long fledgling periods during which food conditions randomly or seasonally change. Here, we show that fledgling mass predicts juvenile survival in the Hawaii Akepa (Loxops coccineus coccineus), an endangered Hawaiian Honeycreeper with high annual adult survival and a two-egg clutch. Juvenile survival of Hawaii Akepa approximated a trimodal pattern of no survival, low survival, and high survival that corresponded to ascending mass classes. Fled...

Demography and conservation of the White-tailed Tropicbird Phaethon lepturus on Aride Island, Western Indian Ocean

The White-tailed Tropicbird Phaethon lepturus breeding population of Aride Island, Seychelles, has experienced a strong decline in the recent past. To predict the future trends of the White-tailed Tropicbird population on Aride Island and understand the urgency of applying management procedures, we developed a population matrix model. We estimated White-tailed Tropicbird adult survival rate over a 12-year period and investigated whether oceanographic conditions (El Nino Southern Oscillation, ENSO, and inter-annual climate variability in the Indian Ocean, Indian Ocean Dipole, IOD) or local factors (Pisonia grandis fruiting events) potentially affect adult survival. Annual adult survival could not be linked to inter-annual variability in oceanographic conditions, but may be more influenced by Pisonia fruiting events, which, overall, accounts for 23.2% of the adult mortality. The growth rate of the population, primarily influenced by annual adult survival, was estimated to be 0.946, which indicates an annual population decline of 5.4%. At the current rate, the probability of extinction of this population would be 99% in 170 years. Management scenarios studied through Monte Carlo simulations, assuming small increments in adult survival and/or breeding success, dramatically reduce the risk of extinction of White-tailed Tropicbirds. Habitat management, in order to maintain an open canopy and little understorey vegetation, appears to be crucial for the conservation of White-tailed Tropicbirds on Aride Island, as has already been shown for other ground-nesting tropical seabirds nesting on forested islands.

Sage Grouse Chick Survival Rates in Jackson Hole

The Greater Sage-grouse (Centrocerus urophasianus) population within Jackson Hole has been declining over the past 60 years (Holloran and Anderson 2004). Currently, several unknown population parameters may affect population models, such as nesting productivity (and annual variation therein), nest initiation and re-nesting rates, sex ratio of chicks produced, chick survival, and annual sub-adult and adult survival rates. While previous research has investigated some of these demographic parameters for the Jackson Hole sage-grouse population (Holloran and Anderson 2004); those estimates may not be adequate due to sample size limitations. Further, there are new constraints on this population due to drastic changes in the wintering habitat from wildfires since those estimates were obtained.

Global climate patterns explain range‐wide synchronicity in survival of a migratory seabird

AbstractTo predict the impact of climate change over the whole species distribution range, comparison of adult survival variations over large spatial scale is of primary concern for long‐lived species populations that are particularly susceptible to decline if adult survival is reduced. In this study, we estimated and compared adult survival rates between 1989 and 1997 of six populations of Cory's shearwater (Calonectris diomedea) spread across 4600 km using capture–recapture models. We showed that mean annual adult survival rates are different among populations along a longitudinal gradient and between sexes. Variation in adult survival is synchronized among populations, with three distinct groups: (1) both females and males of Corsica, Tremiti, and Selvagem (annual survival range 0.88–0.96); (2) both females and males of Frioul and females from Crete (0.82–0.92); and (3) both females and males of Malta and males from Crete (0.74–0.88). The total variation accounted for by the common pattern of variation is on average 71%, suggesting strong environmental forcing. At least 61% of the variation in survival is explained by the Southern Oscillation Index fluctuations. We suggested that Atlantic hurricanes and storms during La Niña years may increase adult mortality for Cory's shearwater during winter months. For long‐lived seabird species, variation in adult survival is buffered against environmental variability, although extreme climate conditions such as storms significantly affect adult survival. The effect of climate at large spatial scales on adult survival during the nonbreeding period may lead to synchronization of variation in adult survival over the species' range and has large effects on the meta‐population trends. One can thus worry about the future of such long‐lived seabirds species under the predictions of higher frequency of extreme large‐scale climatic events.

Human caused mortality in the endangered Scandinavian wolverine population

The wolverine is a relatively long lived mustelid species with low average annual reproduction which in theory makes them sensitive to changes in survival rates. In a multi-year study we monitored 211 radio-marked wolverines to estimate age-specific survival rates and mortality causes in an endangered population. Our data suggests that poaching forms a substantial part of wolverine population dynamics in northern Scandinavia causing up to 60% of adult mortality. Average annual adult survival rate was 0.91. Male and female survival rates did not differ. Twenty-five adult wolverines were confirmed to have died during the study. Fifty-two percent of confirmed adult mortality was human caused. The most important cause of adult mortality was poaching (9). Annual adult survival was lower (0.86) when 15 adult resident wolverines that were assumed to have died due to poaching were included in the analyses. Natural mortality among subadults and adults was less frequent in our study population compared to North American wolverine populations. Adult survival was significantly lower during the snow season (December–May) than during the snow-free season (June–November), while natural mortality was more evenly distributed between seasons. We explain this by the frequency of poaching which is higher during snow season. Our results underline the need to frame the underlying human dimension factors behind poaching to facilitate conservation and management of endangered populations.

VARIABLE WEATHER PATTERNS AFFECT ANNUAL SURVIVAL OF NORTHERN FLICKERS MORE THAN PHENOTYPE IN THE HYBRID ZONE

Abstract Fitness in a hybrid zone is determined both by the reproductive success and the survival of phenotypes. The hybrid zone of Northern Flickers (Colaptes auratus), a common woodpecker, is one of the largest and most well-known hybrid zones in North America. Bounded-hybrid superiority, the most widely accepted hypothesis for the persistence of the zone, suggests hybrids should have equal or higher reproduction or survival than parental types in the zone, but the latter life history trait has never been examined. We analyzed the apparent survival of 1117 flickers over nine years using capture-recapture models and found no evidence that the phenotypic hybrid index influenced survival. Instead, annual adult apparent survival was best modeled according to large-scale weather patterns such as the North Atlantic Oscillation (NAO). During warm phases of the NAO, adult flickers had lower survival compared to cooler phases of NAO. There was no evidence that phenotype influenced the local recruitment of yearli...

Adult Survival of Tropical Roseate Terns Breeding on Aride Island, Seychelles, Western Indian Ocean

Abstract Survival of tropical Roseate Terns (Sterna dougallii) from the western Indian Ocean was modeled using a capture-mark-recapture dataset of 102 breeding adults ringed and resighted on Aride Island, Seychelles, from 2002 to 2007. The effect of covariates reflecting oceanographic conditions and resighting effort was also examined during the modeling. A time-invariant survival rate was best supported by our data, with annual adult survival estimated at 0.807 ± 0.033 (SE). Resighting probability was found to be influenced by sea-surface temperature (SST) anomalies, as expressed by the mean Indian Ocean Dipole mode index recorded during the nonbreeding period. Years of higher SST in the western part of the Indian Ocean in September-April (8 months) corresponded to a lower probability of resighting adults at the colony during the breeding season (May-August), which may be related to a tendency for some adults to refrain from breeding in less favorable years. Comparing our results with temperate studies, ...

Relative longevity and field metabolic rate in birds

Metabolism is a defining feature of all living organisms, with the metabolic process resulting in the production of free radicals that can cause permanent damage to DNA and other molecules. Surprisingly, birds, bats and other organisms with high metabolic rates have some of the slowest rates of senescence begging the question whether species with high metabolic rates also have evolved mechanisms to cope with damage induced by metabolism. To test whether species with the highest metabolic rates also lived the longest I determined the relationship between relative longevity (maximum lifespan), after adjusting for annual adult survival rate, body mass and sampling effort, and mass-specific field metabolic rate (FMR) in 35 species of birds. There was a strongly positive relationship between relative longevity and FMR, consistent with the hypothesis. This conclusion was robust to statistical control for effects of potentially confounding variables such as age at first reproduction, latitude and migration distance, and similarity in phenotype among species because of common phylogenetic descent. Therefore, species of birds with high metabolic rates senesce more slowly than species with low metabolic rates.

Allometric Scaling and Bayesian Priors for Annual Survival of Birds and Mammals

Allometric theory predicts that instantaneous mortality rates scale with body mass with a negative quarter power. Such a relationship would mean that the survival rate of one species is partly predictable from the survival rate of other species. We develop allometric regression models for annual adult survival of birds and mammals, using data collected from the literature. These models conform to the predictions of the allometric theory; the value of negative one-quarter for the scaling parameter is within the 95% credible interval, which is [-0.31, -0.10] for birds and [-0.35, -0.15] for mammals. The predictions are very well supported when evaluated using an independent set of data. The regression models can be used to provide objective and informative Bayesian priors for annual adult survival rates of birds and mammals or to act as a point of comparison in new studies.

Demography of Ferruginous Hawks Breeding in Western Canada

Abstract: We assessed age‐dependent survival, site‐fidelity, and, together with data on prey and reproduction, trends in the population of ferruginous hawks (Buteo regalis) breeding in western Canada. Our analysis included 7,129 ferruginous hawks banded near Hanna, Alberta, and Kindersley‐Alsask, Saskatchewan, from 1972 to 2003. We estimated annual adult survival rate to be 0.708 (SE = 0.024) and first year survival for nestlings was 0.545 (SE = 0.147). Resighting probability was modeled as a constant for nestlings (0.009, SE = 0.010), but it varied among years for adults consistent with our sampling efforts. Band reporting rate was at 0.022 (SE = 0.007) for both nestlings and adults. Fidelity to the study site was 1.00 (SE = 0.000) for adults and 0.035 (SE = 0.014) for nestlings. Nesting density ranged from 3.1 to 14.0 pairs/100 km2 and averaged 9.8 pairs/100 km2. We observed an average clutch size of 3.2 (SE=0.06) and brood sizes of 2.71 (SE=0.07) near Hanna and 2.79 (SE = 0.99) at Kindersley‐Alsask. Richardson's ground squirrels (Spermophilus richardsonii) made up 95% of ferruginous hawk prey. Prey availability was positively correlated with number of offspring near Hanna and Kindersley‐Alsask. We believe the lower than expected adult survival did not result in population decrease; rather, declines in reproduction resulting from declines in the abundance of ground squirrels better explain an observed 4.5‐fold decline in nesting densities during the study. The results suggest that ferruginous hawk management should address prey in addition to habitat management, and that management needs are regional in scope with particular emphasis on the breeding range within the northern Great Plains.

GRASSLAND SONGBIRD SURVIVAL AND RECRUITMENT IN AGRICULTURAL LANDSCAPES: IMPLICATIONS FOR SOURCE–SINK DEMOGRAPHY

Population growth and decline are particularly sensitive to changes in three key life-history parameters: annual productivity, juvenile survival, and adult survival. However, for many species these parameters remain unknown. For example, although grassland songbirds are imperiled throughout North America, for this guild, only a small number of studies have assessed these parameters. From 2002 to 2006, in the agricultural landscape of the Champlain Valley of Vermont and New York, USA, we studied Savannah Sparrow (Passerculus sandwichensis) and Bobolink (Dolichonyx oryzivorus) demography on four grassland treatments: (1) early-hayed fields cut before 11 June and again in early- to mid-July; (2) middle-hayed fields cut once between 21 June and 10 July; (3) late-hayed fields cut after 1 August; and (4) rotationally grazed pastures. We assessed whether these treatments affected adult apparent survival (phi) and recruitment (f), how sensitive these parameters were to the presence of nonbreeders and local dispersal, and the populations' ability to persist in these four habitats. On average, birds using late-hayed fields had > 25% higher apparent survival than those on the more intensively managed early-hayed, middle-hayed, and grazed fields. Overall male phi was 35% higher than female phi, and Savannah Sparrow phi was 44% higher than Bobolink phi. Across all analyses and treatments, apparent survival estimates were 0.58-0.85 for male and 0.48-0.71 for female Savannah Sparrows, and 0.52-0.70 for male and 0.19-0.55 for female Bobolinks. For males of both species, potential nonbreeders decreased the precision of and lowered apparent survival estimates by 25%; female estimates showed little variation with the inclusion of nonbreeders. Inclusion of local dispersal observations increased apparent survival estimates and, in many cases, increased precision, though the effect was stronger for Savannah Sparrows than for Bobolinks, and also stronger for males than for females. High Savannah Sparrow apparent survival rates resulted in stable or near stable populations (lambda approximately 1), particularly in late-hayed and grazed fields, while low Bobolink apparent survival rates resulted in strongly declining populations (lambda < 1) in all treatments.

HIGH SURVIVAL OF IMMATURES IN A LONG-LIVED SEABIRD: INSIGHTS FROM A LONG-TERM STUDY OF THE ATLANTIC PUFFIN (FRATERCULA ARCTICA)

Abstract Survival from fledging to maturity is an important life-history parameter in long-lived species such as seabirds. However, because of the long period of unobservability following fledging, few studies have reported reliable estimates of survival rates for immatures. We estimated survival to maturity of two cohorts of Atlantic Puffin (Fratercula arctica) fledglings from Hornoya in northern Norway using capture–mark–recapture methodology. By considering only juveniles that actually left their nest burrows, we arrived at unbiased estimates of survival rates for immatures. Contrary to many previous studies, annual survival of immatures was not depressed in relation to adult survival. By the age of five years, more than two-thirds of all fledglings are still estimated to be alive. Averaged over this period, annual survival of immatures is estimated as 0.933 (95% confidence interval: 0.806–0.993). This compares to an annual adult survival of 0.943 (0.909–0.965) during the same period. The survival esti...

Population Dynamics of the Concho Water Snake in Rivers and Reservoirs

stochastic transitions between pre-reproductive and reproductive size classes and to allow for the possibility of different survival and capture probabilities for the two classes. We also estimated both the finite rate of increase (l) for a deterministic, stage-based, female-only matrix model using the average litter size, and the average rate of adult population change, l ˆ, which describes changes in numbers of adult snakes, using a direct capture– recapture approach to estimation. Average annual adult survival was about 0.23 and similar for males and females. Average annual survival for subadults was about 0.14. The parameter estimates from the stage-based projection matrix analysis all yielded asymptotic values of l , 1, suggesting populations that are not viable. However, the direct estimates of average adult l for the three subpopulations excluding major reservoirs were l ˆ = 1.26, SE ˆ(l ˆ ) = 0.18 and l = 0.99, SE ˆ(l ˆ ) = 0.79, based on two different models. Thus, the direct estimation approach did not provide strong evidence of population declines of the riverine subpopulations, but the estimates are characterized by substantial uncertainty.

HABITAT FRAGMENTATION LOWERS SURVIVAL OF A TROPICAL FOREST BIRD

Population ecology research has long been focused on linking environmental features with the viability of populations. The majority of this work has largely been carried out in temperate systems and, until recently, has examined the effects of habitat fragmentation on survival. In contrast, we looked at the effect of forest fragmentation on apparent survival of individuals of the White-ruffed Manakin (Corapipo altera) in southern Costa Rica. Survival and recapture rates were estimated using mark-recapture analyses, based on capture histories from 1993 to 2006. We sampled four forest patches ranging in size from 0.9 to 25 ha, and four sites in the larger 227-ha Las Cruces Biological Station Forest Reserve (LCBSFR). We found a significant difference in annual adult apparent survival rates for individuals marked and recaptured in forest fragments vs. individuals marked and recaptured in the larger LCBSFR. Contrary to our expectation, survival and recapture probabilities did not differ between male and female manakins. Also, there was no support for the existence of annual variation in survival within each study site. Our results suggest that forest fragmentation is likely having an effect on population dynamics for the White-ruffed Manakin in this landscape. Therefore, populations that appear to be persisting in fragmented landscapes might still be at risk of local extinction, and conservation action for tropical birds should be aimed at identifying and reducing sources of adult mortality. Future studies in fragmentation effects on reproductive success and survival, across broad geographical scales, will be needed before it is possible to achieve a clear understanding of the effects of habitat fragmentation on populations for both tropical and temperate regions.

BREEDING ECOLOGY OF THE MANGROVE WARBLER (DENDROICA PETECHIA BRYANTI) AND COMPARATIVE LIFE HISTORY OF THE YELLOW WARBLER SUBSPECIES COMPLEX

It is widely accepted that tropical birds differ from temperate species in life-history traits and social behaviors, yet baseline ecological data are lacking for most tropical species and comparative studies often fail to control for phylogenetic influences. Within the Americas, the Yellow Warbler (Dendroica petechia) is ideal for such comparisons because its subspecies encompass a range of life-history strategies; the subspecies include long-distance migrants, temperate–tropical migrants, and tropical residents. We collected baseline data on the breeding ecology of Mangrove Warblers (D. p. bryanti) from southern Mexico (2001–2003) and compared their life-history traits with those of temperate and other tropical subspecies using existing data. Mangrove Warblers actively defended territories year-round during both nonbreeding and breeding seasons. The timing of breeding varied by year, and clutch size averaged 2.9 ± 0.5 [SD] eggs, with both a median and a mode of 3 eggs. Annual estimates of nesting success ranged from 18% to 33%, and nest depredation was the primary cause of nest failure. Annual survival was significantly higher for males (0.65) than for females (0.52) and, given our data, did not vary by age or year. On the basis of a comparative analysis of life-history data from published studies on the Yellow Warbler subspecies complex, we found that most life-history traits differed between tropical and temperate latitudes. Specifically, compared with temperate Yellow Warblers, Mangrove Warblers exhibited longer breeding seasons, smaller clutch sizes, longer incubation and nestling periods, lower nesting success, higher rates of nest depredation, and higher annual adult survival rates.

Recruitment processes in long‐lived species with delayed maturity: estimating key demographic parameters

Long‐lived species show delayed maturity and generally skip breeding sites on a given year, causing difficulties in estimating demographic parameters. A novel multi‐state capture – recapture model (model G for general) is proposed to estimate survival and recruitment. Model G considers long and short periods of non‐attendance at the breeding site. Model G is compared against a reduced model (model R) to test if pre‐breeders skip the studied site a given year, potentially prospecting other breeding habitats.This model is applied to the vulnerable Cory's shearwaters seabird species. As for many species, natal philopatry, pre‐breeding attendance and prospecting play an important role for recruitment into the breeding population. Model G shows that all Cory's shearwaters come back to their natal colony, and attend the colony before recruiting into the breeding population. Moreover, model G is preferred against model R, highlighting that prospecting plays a potentially role in the recruitment processes. Return and recruitment probabilities show similar time variation, suggesting an environmental forcing. The maximum probability of the first breeding is reached at the age of seven years. During the first year the annual survival rate is 0.52 (IC95%=[0.40, 0.64]) and pre‐breeders and adult annual survival rates do not differ, being respectively 0.88, IC95%=[0.83, 0.92] and 0.89, IC95%=[0.88, 0.9].Model G provides an improvement to estimate demographic parameters for long‐lived species life cycle and an adequate framework to test the influence of covariates. Model G is structured by age and breeding status categories, allowing easy further population models.

Fecundity and longevity of roaming dogs in Jaipur, India.

BackgroundEstimates of demographic parameters, such as age-specific survival and fecundity, age at first pregnancy and litter size, are required for roaming dogs (i.e. dogs that are neither confined nor restricted) to assess the likely effect of proposed methods of population control. Data resulting from individual identification of dogs spayed as part of an Animal Birth Control (ABC) programme in Jaipur, India, are used to derive such parameters for the roaming dog population of that city.ResultsThe percentage of females becoming pregnant in any given year was estimated by inspection of over 25,000 females caught for spaying from 1995 to 2006. The point estimate is 47.5% with a 95% confidence interval from 44% to 51%. Adult annual survival of spayed females was estimated by recapture of 62 spayed females from 2002 to 2006. The point estimate is 0.70 (95% confidence interval from 0.62 to 0.78), corresponding to an expected total lifespan of 3.8 years for a spayed female at one year old.ConclusionRecording the pregnancy status of dogs collected for spaying and individual marking of dogs released following spaying can provide estimates of some of the demographic parameters essential for predicting the future effectiveness of an ABC programme. Further, we suggest that recording the number and location of spayed and unspayed dogs encountered by the catching teams could be the most effective way to monitor the size and composition of the roaming dog population.

Annual survival of North American Razorbills (Alca torda) varies with ocean climate indices

According to life-history theory, survival in long-lived animals is not expected to vary greatly with environmental conditions. However, recent studies of a number of seabirds have shown that ocean climate indices such as the Pacific Decadal Oscillation index and sea surface temperature are correlated with adult survival. Here we evaluated whether annual adult survival of Razorbills ( Alca torda L., 1758) at two breeding colonies covaried with oceanographic conditions in the North Atlantic during 1995–2006. We also examined pre-breeder survival (from fledging to age 2). The relationship between local adult survival and the North Atlantic Oscillation and two oceanographic variables (Labrador Current temperature profile and Bay of Fundy sea surface temperature) were evaluated using the program MARK. Capture–mark–recapture data fit the assumptions of the program MARK reasonably well with ĉ values ranging from 1.390 to 2.404. Pre-breeder survival rates were high for Machias Seal Island (Ф = 0.778 ± 0.041) and low for the Gannet Islands (Ф = 0.482 ± 0.033), likely the result of hunting pressure. On Machias Seal Island, constant adult survival (Ф = 0.967 ± 0.028) was the best model; however, time-dependent models that included a climate covariate performed nearly as well. On the Gannet Islands, adult survival (Ф = 0.890 ± 0.053) was negatively correlated with Labrador Current temperature. Overall, our results show significant differences in survival rates across sites over the same time period and highlight the importance of multisite studies and smaller scale climate indices for local populations. In addition, our study contributes to the growing body of evidence that survival in long-lived animals may vary with environmental conditions more than previously expected.