Apparent Survival Probability Research Articles

Diferencias en algunos parámetros demográficos de Oryzomys chapmani (Rodentia: Muridae) asociadas a tres estados sucesionales de bosque mesófilo de montaña en Oaxaca, México

Se estudiaron las diferencias en probabilidades de supervivencia y captura, proporción de sexos y tamaño poblacional en el roedor endémico de México Oryzomys chapmani asociadas a una cronosecuencia constituida por tres estados sucesionales de bosque mesófilo de montaña. El estudio se realizó en la región Sierra Norte de Oaxaca y los tiempos de regeneración de los fragmentos de bosque estudiados fueron 15 (Joven), 40 (Intermedio) y 100 (maduro) años. Se capturaron, marcaron y liberaron 277 ejemplares adultos durante 14 meses. Las probabilidades de supervivencia fueron similares en los bosques Joven e Intermedio, sin fluctuaciones a través del tiempo, mientras que en el Maduro se observó un valor más alto en la temporada seca. Las probabilidades de captura no mostraron variación a través del tiempo en los estados Joven e Intermedio, pero en el Maduro difirieron entre temporadas, con valores más altos en la de lluvias. Los estados Intermedio y Maduro muestran una proporción 1:1 entre sexos, mientras que el Joven se observó un predominio significativo de machos. El tamaño poblacional vario de 42 individuos por hectárea en la temporada de lluvias a 309 en la seca, ambos en el Bosque Maduro.

Resident and transient dynamics, site fidelity and survival in wintering BlackcapsSylvia atricapilla: evidence from capture–recapture analyses

In their winter quarters, migrant birds may either remain within a small area (resident strategy) or move frequently over a large area looking for locally abundant food (transient strategy). It has been suggested that both strategies could simultaneously occur in the same population. We used time‐since‐marking capture–recapture models to infer the coexistence of these two behavioural strategies (transient and resident) among wintering BlackcapsSylvia atricapillausing weekly recapture data over a 7‐year period. A related question is whether Blackcaps, if surviving to the next winter, always return to the same wintering area, so we also used this approach to analyse winter site fidelity and to estimate annual survival probabilities. Model selection supported the existence of heterogeneity in survival estimates for both the within‐season and the interannual survival probabilities, i.e. there was evidence for the existence of transients. It was estimated that 26% of the Blackcaps were resident during the winter. Mean apparent annual survival probability was 0.46 (se = ±0.11). However, there was some evidence suggesting that not all individuals showed winter site fidelity. The estimated proportion of individuals that, if alive, returned to the wintering area was 28%. This is the first study to show the existence of these two behavioural strategies (residence and transience) among wintering Blackcaps, and the first confirming this pattern using capture–recapture models. These models considering transient and resident dynamics may become an important tool with which to analyse wintering strategies.

Apparent Survival and Detection Estimates for PIT‐Tagged Slimy Sculpin in Five Small New Brunswick Streams

AbstractThe slimy sculpin Cottus cognatus is an abundant and widespread benthic fish that inhabits cold lakes and rivers in North America. The objective of this study was to estimate survival and detection probabilities for slimy sculpin in relation to several environmental and biological predictors. Passive integrated transponder (PIT) tags were implanted into 337 adult slimy sculpin in five tributaries of the Kennebecasis River, New Brunswick, Canada. A portable PIT tag antenna was used to search for marked individuals from June 2003 to July 2004. Cormack–Jolly–Seber open population models were used to test several predictions and to estimate apparent survival and detection probabilities. We found that survival was high (73–99%) among sampling events; the average period was about 4 weeks (range, <1–22 weeks). Survival was positively related to fish length and negatively related to maximum stream discharge. The mean detection probability of tagged sculpin was 0.80, but it varied among sampling events and with respect to the minimum electrical current of our antenna and the percentage of boulder substrate at the site. This study demonstrates that a portable PIT tag system can be used in conjunction with capture–mark–recapture models to acquire an understanding of the basic life history characteristics of slimy sculpin and possibly other small‐bodied fish in freshwater systems.

Effects of Radiomarking on Prairie Falcons: Attachment Failures Provide Insights About Survival

From 1999–2002, we attached satellite-received platform transmitter terminals (PTTs) to 40 adult female prairie falcons (Falco mexicanus) on their nesting grounds in the Snake River Birds of Prey National Conservation Area (NCA) in southwest Idaho. We used 3 variations of a backpack harness design that had been used previously on raptors. Each radiomarked falcon also received a color leg band with a unique alphanumeric code. We monitored survival of birds using radiotelemetry and searched for marked birds on their nesting grounds during breeding seasons after marking. Because 6 falcons removed their harnesses during the first year, we were able to compare survival rates of birds that shed PTTs with those that retained them. We describe a harness design that failed prematurely as well as designs that proved successful for long-term PTT attachment. We resighted 21 marked individuals on nesting areas 1–5 years after they were radiomarked and documented 13 mortalities of satellite-tracked falcons. We used a Cormack-Jolly-Seber model to estimate apparent survival probability based on band resighting and telemetry data. Platform transmitter terminals had no short-term effects on falcons or their nesting success during the nesting season they were marked, but birds that shed their transmitters increased their probability of survival. Estimated annual survival for birds that shed their transmitters was 87% compared to 49% for birds wearing transmitters. We discuss possible reasons for differences in apparent survival rates and offer recommendations for future marking of falcons.

ENCOUNTER, SURVIVAL, AND MOVEMENT PROBABILITIES FROM AN ATLANTIC PUFFIN (FRATERCULA ARCTICA) METAPOPULATION

Several weaknesses in our understanding of long-lived animal populations have persisted, mainly due to a prevalence of studies of a single local population at the expense of multisite studies. We performed a multisite capture–mark–resight analysis using 2050 Atlantic Puffins (Fratercula arctica) banded as chicks on four islands (colonies) over 24 years in the Gulf of Maine, USA and Canada. Within program MARK, encounter, apparent survival, pre-breeding movement (PBM; annual movements between colonies prior to breeding), and natal dispersal (ND) probabilities were modeled as functions of age, colony, and several covariates. Information-theoretic model selection criteria and estimated model effect sizes were used to identify important effects and select models to estimate parameters. Encounter probabilities were extremely variable (0.10–0.95) and declined annually starting six years after bands were applied, due to changes in resighting effort, and band wear, respectively. Colony-dependent survival probabil...

Long-term variation in survival rates of Sand Martins Riparia riparia: dependence on breeding and wintering ground weather, age and sex, and their population consequences

Capsule Survival rates of Sand Martins are driven by variation in rainfall on the wintering grounds prior to their arrival and in the breeding area in the previous summer; inter-annual changes in abundance also show strong correlations with survival. Aims To investigate the demography underlying long-term changes in population size in a large study area in central England, focusing primarily on describing the variation in survival and identifying its causes and demographic consequences. Methods An intensive mark–recapture effort was undertaken on Sand Martin colonies in an area of over 400 km2 of Nottinghamshire, England, from 1967 to 1992. The resulting data were analysed using the program MARK to investigate variation in survival with respect to sex, age, time and variables describing the key climatic conditions on the breeding and wintering grounds. The same variables were also tested against data on the age-structure of the population. Results The average annual apparent survival probabilities of adult males and females were not significantly different (males 0.312 ± 0.026 se; females 0.289 ± 0.026 se). There was no obvious long-term temporal trend in survival rates, but considerable fluctuations occurred between years. There was a positive relationship between annual survival rates and Sahel rainfall, but a stronger, negative, relationship between survival and the previous summer's rainfall in the study area. These relationships were reflected in correlations with the annual population level and the annual percentage change in the population, but other evidence suggests that rainfall on the breeding grounds during the breeding season has a further important effect on productivity. Conclusion The Sand Martin population in the study area was limited by climatic conditions, primarily rainfall in the breeding area, but also rainfall on the wintering grounds. These climatic effects operated mostly by influencing annual survival, but also probably affected productivity. This contrasts with published results for Sand Martins in central Europe, which have been found to be more strongly affected by rainfall on the wintering grounds and for which relationships between survival and abundance are obscured by fluctuations in immigration and emigration. The importance of rainfall on the breeding grounds as a negative influence on over-winter survival is a novel finding both in Sand Martin biology and in the context of the environmental influences on passerine demography in general.

SITE OCCUPANCY, APPARENT SURVIVAL, AND REPRODUCTION OF CALIFORNIA SPOTTED OWLS IN RELATION TO FOREST STAND CHARACTERISTICS

Abstract The California spotted owl (Strix occidentalis occidentalis) has been at the center of political and administrative debate due to its association with commercially valuable forest. Several studies have compared the forest cover types used by California spotted owls with the cover types that are generally available, establishing the association between spotted owls and old/large tree components of forests at the landscape scale. We sought a deeper understanding of spotted owl habitat associations in areas in which owls had already selected territories. We mapped and classified vegetation within circular plots (radius 2.4 km) around 67 spotted owl sites in northeastern California, USA. We evaluated the relationships between habitat composition within the different owl sites and variation in (1) nest success (1990–2000) and (2) site occupancy, apparent survival probability, and reproductive output (1993–1998). All analyses included data representing 2 spatial scales: core area (814 ha) and nest area...

Survival probability estimates for immature green turtles Chelonia mydas in the Bahamas

Green turtles Chelonia mydas in the Atlantic undergo a complex series of development- al migrations, moving long distances among foraging grounds. The study of the ecology and demog- raphy of these foraging populations is hampered by a lack of estimates of survival probabilities for immature stages. In addition, for all species of sea turtles, estimates of survival probabilities have repeatedly been identified as the greatest requirement for improving models of population dynamics and plans for the management and conservation of these endangered and threatened species. We use data from long-term capture-mark-recapture studies of 2 sampling populations of immature green turtles in the Bahamas—Union Creek, Great Inagua from 1978 through 2001, and Conception Creek, Conception Island from 1989 through 2001—to generate estimates of annual survival proba- bilities. We employ a joint analysis of live-recapture and dead-recovery data (Burnham model) to generate estimates of true survival and permanent emigration probabilities for the Union Creek sam- pling population. Because fewer dead-recovery data were available for the Conception Creek sam- pling population, we used a Cormack-Jolly-Seber modeling approach to estimate an apparent annual survival probability of 0.680, which confounds mortality and permanent emigration. Our best esti- mate of true annual survival probability for Union Creek green turtles, protected from human- induced mortality, is 0.891. High survival probabilities in immature stages are necessary for species such as sea turtles with long lifespans and late sexual maturity to maintain stable populations. After green turtles emigrated from Union Creek, annual survival probability declined to 0.761 as the tur- tles were no longer protected from human-induced mortality, demonstrating the negative effect of this mortality on the future of green turtle populations in the Caribbean. This study reports the first application of the joint analysis of live-recapture and dead-recovery data to sea turtle populations and demonstrates the advantages of this modeling approach.

APPARENT SURVIVAL RATES OF WESTERN SANDPIPER (CALIDRIS MAURI) WINTERING IN NORTHWEST BAJA CALIFORNIA, MEXICO

Abstract To estimate annual apparent local survival, we collected capture–resighting data on 256 individually marked male Western Sandpipers (Calidris mauri) wintering at Estero de Punta Banda, Mexico, between 1994–1997. A hierarchical modeling approach was used to address the effect of age class and year on survivorship rates. The best-fit model included a constant apparent survival probability (ϕ = 0.489; 95% CI = 0.410–0.569), but several models fit nearly as well, and averaging among the top five, to account for model uncertainty, suggested that adults had somewhat higher values than juveniles (ϕ = 0.490 ± 0.051 vs. 0.450 ± 0.067). Detection probability was substantially higher for adults than for juveniles (p = 0.741 vs. p = 0.537). Those apparent survival estimates are low compared with those from other studies of Western Sandpipers at breeding and other nonbreeding locations, and substantially lower than the true survivorship rates expected for small sandpipers in general. We interpret these result...

Apparent Survival Rates of Western Sandpiper (Calidris Mauri) Wintering in Northwest Baja California, Mexico

AbstractTo estimate annual apparent local survival, we collected capture–resighting data on 256 individually marked male Western Sandpipers (Calidris mauri) wintering at Estero de Punta Banda, Mexico, between 1994–1997. A hierarchical modeling approach was used to address the effect of age class and year on survivorship rates. The best-fit model included a constant apparent survival probability (ϕ = 0.489; 95% CI = 0.410–0.569), but several models fit nearly as well, and averaging among the top five, to account for model uncertainty, suggested that adults had somewhat higher values than juveniles (ϕ = 0.490 ± 0.051 vs. 0.450 ± 0.067). Detection probability was substantially higher for adults than for juveniles (p = 0.741 vs. p = 0.537). Those apparent survival estimates are low compared with those from other studies of Western Sandpipers at breeding and other nonbreeding locations, and substantially lower than the true survivorship rates expected for small sandpipers in general. We interpret these results as indicating that this site is of below average quality for nonbreeding male Western Sandpipers.

ESTIMATING DORMANCY AND SURVIVAL OF A RARE HERBACEOUS PERENNIAL USING MARK–RECAPTURE MODELS

Mark-recapture statistics have rarely been applied to plants, yet they can be useful for estimating plant demographic traits where individuals may be missed or unob- servable. We applied mark-recapture statistics based on an information theory approach to estimate annual probabilities of dormancy in a five-year study of a threatened, perennial plant, the small yellow lady's slipper orchid ( Cypripedium calceolusssp. parviflorum (Sal- isb.) Fernald). The aboveground states of 548 genets in eight patches were monitored over five years. Apparent survival probabilities (f), corrected for dormancy, were calculated. The best-fit model suggested that apparent survival was constant throughout the study for all patches, while dormancy varied additively with time among patches. The mean prob- ability of dormancy was 0.320 6 0.024, with a mean maximum overestimation of 0.067 as calculated using an estimate of the probability of detection. Dormancy typically lasted for no longer than two consecutive years, although dormancy as long as four years was observed. Dormancy displayed a strong covariate relationship with spring frost days, al- though effects of precipitation and mean spring temperature were almost equally strong. Mean apparent survival probabilities were high in each patch ( f5 0.878), but dormancy probabilities varied considerably among patches (d 5 0.188-0.672). Conventional re- sprouting probabilities underestimated apparent survival by a mean difference of 0.288 (range: 0.150-0.589). This novel application of mark-recapture statistics to plant demog- raphy allowed robust survival estimates that accounted for uncertainty due to an unob- servable, dormant life stage.

Demography of the California Spotted Owl in Northeastern California

Abstract We estimated age-specific survival (ϕ), fecundity (b), and the finite rate of population change (λ) of California Spotted Owls (Strix occidentalis occidentalis) over a 10-year period (1990–1999). Two hundred nineteen juvenile and 200 subadult or adult owls were banded at 90 sites, with a combined total of 1080 captures. Least-squares mean estimates (± SE) of fecundity (# female fledglings per territorial female) over all years were 0.065 ± 0.066 for subadults (n = 33) and 0.291 ± 0.065 for adults (n = 381). Estimated annual apparent survival probability was 0.333 ± 0.055 for juveniles and 0.827 ± 0.015 for subadults and adults combined. Using these estimates to construct a four-stage projection matrix, the finite rate of population change, λ, was 0.910 ± 0.025. This value of λ suggests an annual rate of decline in the territorial population of 9% per year over the period of study. Elasticity analyses showed λ to be most sensitive to variation in adult female survival. However, the standard devia...