New publication on Storm Petrel population dynamics !

Matović, N, Cadiou, B, Oro, D. and Sanz-Aguilar A. 2017. Disentangling the effects of predation and oceanographic fluctuations in the mortality of two allopatric seabird populations

 Population Ecology, 59:225–238, doi: 10.1007/s10144-017-0590-5

 

Photo By A. Caldas (Flickr)

Abstract : Life-history traits of migratory seabirds are influenced by changing conditions at breeding and wintering grounds. Climatic conditions and predation are known to impact populations’ survival rates, but few studies examine their effect simultaneously. We used multievent capture–recapture models to assess mortality due to environmental conditions and predation in breeding European storm petrels (Hydrobates pelagicus) in two allopatriccolonies  (Mediterranean and Atlantic). Predatory mortality at the colonies showed annual variation, being around 0.05 in certain years. Mortality at sea differed between the two oceanic basins, and was lower in the Mediterranean colony [0.11, 95% CI (0.09, 0.14)] when compared to the Atlantic colony [0.18, 95% CI (0.15, 0.22)]. The Western Mediterranean Oscillation index (WeMOi)  explained 57%of the temporal variability in mortality of Mediterranean breeders. In comparison, 43% of the temporal variability in mortality of Atlantic breeders was explained by the winter St Helena index (wHIX) and El Niño-Southern Oscillation index (wENSO). Our results suggest that Mediterraneanbreeders remain in this basin for wintering where they may face lower migratory costs and more favourable environmental conditions. In contrast, Atlantic breeders’ mortality may be due to higher cost of migration, changing upwelling conditions in the Benguela current  and heavy storms over their migratory route during La Niña events. This study underlines the importance of modelling separately different causes of mortality when testing the effects of climatic covariates.

 

New Publication on Ferreret, the Majorcan midwife toad !

Pinya, S., Tavecchia,G. and Valentín Pérez-Mellado, V. Population model of an endangered amphibian: implications for conservation management  Endangered Species Research, 34: 123–130, doi.org/10.3354/esr00835

From Wikipedia.com

Abstract: Amphibian populations are declining worldwide, but for many taxa, robust estimates
of demographic parameters to assess population state or trends are scarce or absent.
robust estimates of adult apparent survival of the endemic Majorcan midwife toad Alytes muletensis using individual capture-recapture data collected over 4 yr in a 60 m2 cistern. Moreover, we combined the vital rates into a stage-structured population model to estimate the ex pected longterm growth rate of the population. Apparent survival estimates of males and females were similar (0.737 ± 0.042 and 0.726 ± 0.045, respectively) indicating that the egg-carrying behavior of males, typical of this species, does not reduce its survival probability. We found evidence of a low local survival of juveniles compared with adults, most likely due to permanent dispersal. Adult population size estimation provided higher tadpole:adult ratios than previously reported for this endangered species, suggesting an overestimation of the previous adult population size. Model projections suggested a stable population, since λ, the expected asymptotic growth rate of the population, was close to 1.00.

Full text here

Upcoming CMRR workshop 2017. Apply now !

Workshop on Capture-Mark-Recapture and -Recovery analysis 2017 : you can subscribe now!

The introductory course aims to introduce students, researchers and environmental managers to the theory and practical aspects of the analysis of capture-mark-recapture and –recovery. 
We will focus on how to estimate survival, recruitment and dispersal probabilities in natural populations.
The course is based on theoretical classes as well as practical sessions with real and simulated data.
No previous knowledge on capture-mark-recapture or capture-mark-recovery analyses is necessary.

 

If you want to subscribe send message to : g.tavecchia-at-uib.es

For more information on the program and course payment : http://populationecologygroup.blogspot.com.es/p/workshop.html

New publication : surviving at high elevation !

Bastianelli, G., Tavecchia, G., Meléndez, L. Seoane, J., Obeso, J. R. and Laiolo, P. 2017.
Surviving at high elevations: an inter- and intra-specific analysis in a mountain bird community Oecologia doi:10.1007/s00442-017-3852-1

Photo: e.wikipedia.org

Abstract: Elevation represents an important selection agent on self-maintenance traits and correlated life histories in birds, but no study has analysed whether life-history variation along this environmental cline is consistent among and within species. In a sympatric community of passerines, we analysed how the average adult survival of 25 open-habitat species varied with their elevational distribution and how adult survival varied with elevation at the intra-specific level. For such purpose, we estimated intra-specific variation in adult survival in two mountainous species, the Water pipit (Anthus spinoletta) and the Northern wheatear (Oenanthe oenanthe) in NW Spain, by means of capture–recapture analyses. At the inter-specific level, high-elevation species showed higher survival values than low elevation ones, likely because a greater allocation to self-maintenance permits species to persist in alpine environments.

Photo : larsfoto.es

At the intra-specific level, the magnitude of survival variation was lower by far. Nevertheless, Water pipit survival slightly decreased at high elevations, while the proportion of transient birds increased. In contrast, no such relationships were found in the Northern wheatear. Intra-specific analyses suggest that living at high elevation may be costly, such as for the Water pipit in our case study. Therefore, it seems that a species can persist with viable populations in uplands, where extrinsic mortality is high, by increasing the investment in self-maintenance and prospecting behaviours.

New Publication on Storm Petrels !

Hernández, N., Oro, D and Sanz-Aguilar, A., Environmental conditions, age and senescence differentially influence survival and reproduction in the Storm Petrel. 2017. Journal of Ornithology. Volume 158, pp 113–123. DOI: 10.1007/s10336-016-1367-x

Abstract: Demographic parameters in wild populations are expected to be shaped by individual covariates and environmental variability. Thus, the understanding of the effects of age and/or environmental conditions on variability in vital rates is of special importance in ecological and evolutionary studies. Early age-related improvements in survival and reproduction and later declines due to senescence are expected, above all in long-lived species. Survival in these species is predicted to be a more conservative parameter than reproduction, thereby giving rise to less temporal variability. We studied age-dependent patterns of survival and breeding success in a long-lived seabird, the Mediterranean Storm Petrel Hydrobates pelagicus melitensis, and the additive influence of individual heterogeneity and environmental climatic variables using 22 years of individual-based data (1993–2014). The North Atlantic Oscillation index (NAO) and sea surface temperature (SST) were selected as proxies of environmental conditions in both breeding and wintering areas. Our results show that vital rates improved with age for both survival and breeding success. A slow effect of senescence at older ages was detected for breeding success, whereas models did not disentangle the occurrence or the absence of actuarial senescence. Reproduction was also influenced by the age of first observed reproduction: at the same age, more experienced birds that recruited earlier had a higher breeding success than less experienced ones. Breeding success (but not survival) also showed great temporal variability in accordance with theoretical predictions. Neither the NAO nor the SST explained this variability, probably because petrels feed on lower trophic levels than most pelagic seabirds and other physical features such as river runoffs and winds may be involved, as well as other environmental stressors such as predation by sympatric gulls.

New publication on Egyptian vulture demographic parameters!

Sanz-Aguilar, A., Cortés-Avizanda, A., Serrano, D., Blanco, G., Ceballos, O., Grande, J.M., Tella, J.L., Donázar, J.A.: Sex- and age-dependent patterns of survival and breeding success in a long-lived endangered avian scavenger. Scientific Report, 7 2017 Article number 40204, doi: 10.1038/srep40204

 Abstract. In long-lived species, the age-, stage- and/or sex-dependent patterns of survival and reproduction determine the evolution of life history strategies, the shape of the reproductive value, and ultimately population dynamics. We evaluate the combined effects of age and sex in recruitment, breeder survival and breeding success of the globally endangered Egyptian vulture (Neophron percnopterus), using 31-years of exhaustive data on marked individuals in Spain. 

Photo: J. Bas

Mean age of first reproduction was 7-yrs for both sexes, but females showed an earlier median and a larger variance than males. We found an age-related improvement in breeding success at the population level responding to the selective appearance and disappearance of phenotypes of different quality but unrelated to within-individual aging effects. Old males (≥8 yrs) showed a higher survival than both young males (≤7 yrs) and females, these later in turn not showing aging effects. Evolutionary trade-offs between age of recruitment and fitness (probably related to costs of territory acquisition and defense) as well as human-related mortality may explain these findings. Sex- and age-related differences in foraging strategies and susceptibility to toxics could be behind the relatively low survival of females and young males, adding a new concern for the conservation of this endangered species.

New Publication on modelling dispersal to unobservable sites !

Tavecchia, G., Sanz-Aguilar, A. and Cannell, B. Modelling survival and breeding dispersal to unobservable nest stes. Wildlife Research 43(5) 411-417 http://dx.doi.org/10.1071/WR15187

Context: Demographic parameters in wildlife populations are typically estimated by monitoring a limited number of individuals in observable sites and assuming that these are representative of the whole population. If individuals permanently disperse to unobservable breeding sites, recruitment and immature survival are expected to be negatively biased and breeding-site fidelity cannot be measured.

Photo: Leighton De Barros

Aims: To develop a method to obtain unbiased estimates of survival, recruitment and breeding dispersal when individuals can move to, or recruit in, unobservable sites.
Methods: We used the flexibility of multi-event capture–recapture models to estimate dispersal and recruitment to unobservable sites, merging observations made at two sites within the same breeding locations. We illustrated the model with data on little penguin (Eudyptula minor) breeding in artificial as well as in natural nests. Natural nests are unknown or inaccessible and birds in these sites remain unobservable. Encounters at beaches surrounding the colony suggested that marked animals can permanently move to unobservable nests. We built the multi-event model considering two possible states of the individuals (alive breeding in a nest box and alive in a natural nest) and three types of observations (encountered at a nest only, encountered at the beach only and encountered at both places). This model ensured that the breeding dispersal to unobservable places became estimable.
Key results: Results indicate that the estimated survival was 8% higher than when recaptures at artificial nests were analysed alone. Also, fidelity to artificial nests was 12% lower than to natural nests. This might reflect the greater availability of natural sites or, alternatively, a heterogeneity between these two types of nest.
Conclusions: We obtained an estimate of local survival of little penguins breeding at Penguin Island that incorporates the permanent migration to unobservable sites and found an asymmetric dispersion towards natural nests.
Implication: Our conclusions suggest a need for more careful treatment of data derived from artificial sites alone, as demographic parameters might be underestimated if animals prefer natural breeding sites or if they are in greater proportion compared with artificial ones. The analytical approach presented can be applied to many biological systems, when animals might move into inaccessible or unobservable breeding sites.

WORKSHOP ON CAPTURE-RECAPTURE AND -RECOVERY ANALYSIS, 21-25 November, Mallorca, Spain

UPCOMING WORKSHOP : WORKSHOP ON CAPTURE-RECAPTURE AND -RECOVERY ANALYSIS

21-25 November 2016, Mallorca, SPAIN

Photo: F. Sergio

The course aims to introduce students, researchers and environmental managers to the theory and practical aspects of the analysis of capture-mark-recapture and –recovery data to estimate survival, recruitment and dispersal probabilities. The course is based on theoretical classes as well as practical sessions with real and simulated data.



Information here  or contact directly  g.tavecchia-at-uib.es
 
 Dead line for registration: October 2016
Places: 20

New publication on spring population dynamics of lizards

Pérez-Mellado, V., Garcia-Diez, T., Hernández-Estévez, J.A. & Tavecchia, G. : Behavioural processes, ephemeral resources and spring population dynamics of an insular lizard, Podarcis lilfordi (Squamata: Lacertidae). Italian Journal of Zoology doi: 10.1080/11250003.2015.1093035


Abstract: Temporal changes in adult sex ratio of animal populations might be due to differences in movements, survival or detection probabilities. We used data from an intensive capture–mark–recapture study of 720 lizards at the islet of Aire (Balearic Islands, Spain) to investigate the demographic mechanisms underlying the spring uneven sex ratio. We simultaneously estimated survival (f), the proportion of transient animals (p) and the probability of recapture (p) of lizards at the study plot.

Photo: G. Tavecchia

We then estimated population size using open population models for individually based data and compared these with the observed values. Results indicated that males had a higher probability of recapture than females, but this was not sufficient to generate the observed male-biased sex ratio. The proportion of transient males decreased at the end of spring in parallel with the end of the blooming period of the dead horse arum, Helicodiceros muscivorus, a short-lasting food and thermoregulation resource for lizards during spring. Changes in the proportion of transients suggested that sex-dependent movements, most likely linked to a monopolising behaviour of this plant resource, were responsible for the observed difference in the number of males and females. Our results reveal how the interplay of behavioural and ecological factors explains short-term changes in population dynamics and shapes the movement patterns within the island.

New publication on the survival of Burrowing owls (Athene cunicularia) !

Rebolo-Ifrán, N.,  Carrete, M., Sanz-Aguilar, A., Rodríguez-Martínez, S., Cabezas, S., Marchant, T., Bortolottu, G. and Tella, J. L. (2015). Links between fear of humans, stress and survival support a non-random distribution of birds among urban and rural hábitats. Scientific Reports 5:13723.  DOI: 10.1038/srep13723

Photo: Natalia Rebolo

Abstract:Urban endocrine ecology aims to understand how organisms cope with new sources of stress and maintain allostatic load to thrive in an increasingly urbanized world. Recent research efforts have yielded controversial results based on short-term measures of stress, without exploring its fitness effects. We measured feather corticosterone (CORT_f, reflecting the duration and amplitude of glucocorticoid secretion over several weeks) and subsequent annual survival in urban and rural burrowing owls. This species shows high individual consistency in fear of humans (i.e., flight initiation distance, FID), allowing us to hypothesize that individuals distribute among habitats according to their tolerance to human disturbance. FIDs were shorter in urban than in rural birds, but CORT_f levels did not differ, nor were correlated to FIDs. Survival was twice as high in urban as in rural birds and links with CORT_f varied between habitats: while a quadratic relationship supports stabilizing selection in urban birds, high predation rates may have masked CORT_f-survival relationship in rural ones. These results evidence that urban life does not constitute an additional source of stress for urban individuals, as shown by their near identical CORT_f values compared with rural conspecifics supporting the non-random distribution of individuals among habitats according to their behavioural phenotypes.

New Publication on the effect of tagging birds

Sergio, F., Tavecchia, G., Taferna, A., López Jimenez, L. Blas, J., De Stephanis, R. Marchant, T. A., Kumar, N. and Hiraldo, F. 2015 No effect of satellite tagging on survival, recruitment, longevity, productivity and social dominance of a raptor, and the provisioning and condition of its offspring. J. App. Ecol. Accepted.

Abstract:

1.The deployment of electronic devices on animals is rapidly expanding and producing leapfrog advances in ecological knowledge. Even though their effects on the ecology and behaviour of the marked subjects are potentially important, less than 10% of the studies are accompanied by an evaluation of impact, and comprehensive, long-term assessments have been few. Therefore, there is an urgent need to test for impacts, especially for tags that are heavy and deployed for long time periods, such as satellite transmitters.

Photo: F. Sergio

2.We marked 110 individuals of a medium-sized, migratory raptor, the black kite Milvus migrans, with GPS satellite tags, representing about 4% of the body mass and attached as backpacks through a Teflon harness. Tagged individuals were compared to control animals of similar sex, age and breeding status for a large number of behavioural, condition-related and ecological traits.

3.Despite a sample size 2–3-fold greater than most previous assessments that reported significant impacts, there was no detectable difference between tagged and control individuals in key vital rates such as survival probability, longevity, recruitment, age of first breeding, reproductive performance and timing of breeding.

4.Tagged and untagged kites showed similar social dominance during fights over food and a similar capability to provision nestlings, which prevented carry-over effects on the stress levels and condition of their offspring.

5.Synthesis and applications. Radio-marking studies are growing exponentially in the current “movement ecology era” and impact assessments will be ever more important. In principle, tags of up to 4% mass-load can be deployed without apparent harm on some avian soaring species, but impacts should be properly evaluated on a case-by-case basis. Resilient species for which impacts seem weak could be used as early warning systems for trials of new devices: if impacts are observed, they are likely to be even greater on more vulnerable species. Finally, individual fatalities caused by marking should be taken into serious account, but comprehensively evaluated in the light of broader population-level impacts. Future initiatives to minimize tagging impacts could include more stringent licensing criteria enforcing attendance at training courses or incorporation of impact evaluations into study designs, increased availability of training courses for tagging, and enhanced sharing of information through blogs, workshops or specialized journal sections.