New Publication on Yellow-Legged Gull and PAFS

Real, E., Oro, D., Martinez-Abrain, A., Igual, J.-M., Bertolero, A., Bosch, M.and Tavecchia, G., 2017. Predictable anthropogenic food subsidies, density-dependence and socio-economic factors influence breeding investment in a generalist seabird  Journal of Avian Biology, 48: 001–009

doi: 10.1111/jav.01454

Abstact:  Recent European policies on the ban of fishing discards and the closure of open-air landfills are expected to reduce predictable and abundant food resources for generalist seabirds. In order to forecast the consequences of this reduction on seabird breeding investment it is important to understand whether diverse anthropogenic foraging resources act synergistically or not and whether their influence is mediated by density-dependent mechanisms.

To assess these effects at large spatio-temporal scale, we measured mean egg volume as a proxy of breeding investment in ca 5000 three-egg clutches of the yellow-legged gull Larus michahellis from 20 colonies of the Western Mediterranean, located both along European and African coasts. In European gull colonies, egg volume increased with the availability of fishing discards and landfills in the vicinity of the colony. However, the landfill effect was weaker than the effect of fishing discards, probably due to the lower quality of waste as food for gulls. In contrast, none of the anthropogenic food subsidies influenced egg volume in African colonies, likely due to socio-economic differences (i.e. a much lower availability and predictability of both discards and waste food. Finally, results showed that the positive association between fishing discards and open-air landfills on egg volume was mediated by negative density-dependent mechanisms probably related to an increase in competition for food.

New Publication on the multidimensional value of long-term studies !

Tavecchia, G., Oro, D., Sanz-Aguilar, A., and Béchet, A. 2017. The multidimensional value of long-term individual.based studies: more than lots of data. Avocetta 41: 19-21

With the present rate of biodiversity loss and the profound effects of global changes, population and conservation ecologists face new questions. Many of these are related to how fast individuals can adapt to the strength and pace of environmental variability and can only be answered using individual data collected over long-term (Long Terms Individual Based Studies). Beside this undoubted scientific value, a 20 – 30 years study is likely to have trained several generations of scientists, fostered collaborations between a large number of research institutes and promoted public awareness on scientific themes and wildlife conservation problems. With current public systems providing funds for 3 to 4 years, it is increasingly difficult to initiate and maintain a long-term individual based study. As a consequence, many field studies end before time, without reaching the number of years or the amount of data needed to meet current scientific challenges and to demonstrate their educational value.Here, we argue that the value of LTIBS is multidimensional and it grows steadily with time. How and when does a long-term field study become important? [..] continue reading here

This text is in honor of Dr. Alan Roy Johnson (1941-2014, Photo), Dr. Heinz Hafner (1940-2003) and other pioneers of LTIBS. By focusing the attention on the multidimensional value of LTIBS we aimed to pay a tribute to them and to those people who, thanks to their passion, personal sacrifices and tenacity are keeping these projects alive.

 

A. Johnson (photo. H. Hôte)

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

New Publication on Spoonbill population dynamics!

Tenan S, Fasola M, Volponi S, Tavecchia G. Conspecific and not performance-based attraction on immigrants drivescolony growth in a waterbird. J Anim Ecol. 2017;00:1–8. https://doi.org/10.1111/1365-2656.12690

Abstract

1. Local recruitment and immigration play an important part in the dynamics and growth of animal populations. However, their estimation and incorporation into open population models is, in most cases, problematic. We studied factors affecting the growth of a recently established colony of Eurasian spoonbill (Platalea leucorodia) and assessed the contribution of local recruits, i.e. birds born in the colony, and immigrants, i.e. birds of unknown origin, to colony growth.
2. We applied an integrated population model that accounts for uncertainty in breeding state assignment and merges population surveys, local fecundity and individual longitudinal data of breeding and non-breeding birds, to estimate demographic rates and the relative role of recruitment and immigration in driving the local dynamics. We also used this analytical framework to assess the degree of support for the ‘performance-based’ and ‘conspecific attraction’ hypotheses as possible mechanisms of colony growth.
3. Among the demographic rates, only immigration was positively and significantly correlated with population growth rate. In addition, the number of immigrants settling in the colony was positively correlated with colony size in the previous and current year, but was not correlated with fecundity of the previous year.
4. Our results suggest that the variation in immigration affected colony dynamics and that conspecific attraction likely triggered the relevant role of immigration in the growth of a recently formed waterbird colony, supporting the need of including immigration in population analysis.

You can see press release (in Italian) following the links belows:
http://www.ilvelino.it/it/article/2017/06/08/oltre-500-esemplari-di-spatola-nel-delta-del-po/6a079c85-14eb-4359-9659-07fdbd153b93/

https://www.galileonet.it/2017/06/la-spatola-nel-delta-del-po-ama-la-compagnia/

http://www.quotidiano.net/benessere/animali/animali-spatola-po-1.3184337

http://www.italiaambiente.it/2017/06/08/uccello-spatola-sul-delta-del-po-due-cinquecento-28-anni/

http://www.greencity.it/ambiente/9472/oltre-500-esemplari-di-spatola-nel-delta-del-po.html

http://www.meteoweb.eu/2017/06/ambiente-ispra-uno-studio-rivela-la-singolare-diffusione-di-uccello-spatola-nel-delta-del-po/914077/

http://www.periodicodaily.com/2017/06/09/oltre-500-esemplari-di-spatola-nel-delta-del-po/

https://www.ladeadellacaccia.it/index.php/oltre-500-esemplari-di-spatola-nel-delta-del-po-45712/

A work by the GEP selected for the virtual issue "Demography Behind the Population" (BES)

The work by Sanz-Aguilar et al. has been selected for the virtual issue Demography Behind the Population edited by the British Ecological Society. Read Ana's work here Well done Ana!

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 colonization in social species !

Payo-Payo, A., Genovart, M., Sanz-Aguilar, A., Greño, J.L., García-Tarrasón, ., Bertlero A. and Oro, D., Colonisation in social species: the importance of breeding experience for dispersal in overcoming information barriers. Scientific Report. doi:10.1038/srep42866

Abstract: Studying colonisation is crucial to understand metapopulations, evolutionary ecology and species resilience to global change. Unfortunately, few empirical data are available because field monitoring that includes empty patches at large spatiotemporal scales is required.

from wikipedia.com

We examine the colonisation dynamics of a long-lived seabird over 34 years in the western Mediterranean by comparing population and individual data from both source colony and the newly-formed colonies. Since social information is not available, we hypothesize that colonisation should follow particular dispersal dynamics and personal information must be crucial in decision making. We test if adverse breeding conditions trigger colonisation events, if personal information plays a role in colonisation and if colonisers experience greater fitness. Our results show a temporal mismatch between colonisation events and both density-dependence and perturbations at the source colony, probably because colonisers needed a longer prospecting period to compensate for the lack of public information. Colonisers were mostly experienced individuals gaining higher breeding success in the new colony. Our results highlight the demographic value that experienced individuals can have on metapopulation dynamics of social long-lived organisms.