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/

New Publication on the role of dispersal in animal populations

Tavecchia, G., Tenan, S., Pradel, R., Igual, J.-M., Genovart, M. and Oro, D. 2016 : Climatic-driven vital rates do not always mean climate-driven population. Global Change Biology. doi10.1111/gcb.13330

Abstract: Current climatic changes have increased the need to forecast population responses to climate variability. A common approach to address this question is through models that project current population state using the functional relationship between demographic rates and climatic variables. We argue that this approach can lead to erroneous conclusions when interpopulation dispersal is not considered. We found that immigration can release the population from climate-driven trajectories even when local vital rates are climate dependent. We illustrated this using individual-based data on a trans-equatorial migratory seabird, the Scopoli's shearwater Calonectris diomedea, in which the variation of vital rates has been associated with large-scale climatic indices. We compared the population annual growth rate λ_i, estimated using local climate-driven parameters with ρ_i, a population growth rate directly estimated from individual information and that accounts for immigration. While λ_i varied as a function of climatic variables, reflecting the climate-dependent parameters, ρ_i did not, indicating that dispersal decouples the relationship between population growth and climate variables from that between climatic variables and vital rates. Our results suggest caution when assessing demographic effects of climatic variability especially in open populations for very mobile organisms such as fish, marine mammals, bats, or birds. When a population model cannot be validated or it is not detailed enough, ignoring immigration might lead to misleading climate-driven projections.

New Publication on the rescue effect in Scopoli's Shearwaters !

Sanz-Aguilar, A.; Igual, J.M.; Tavecchia, G.; Genovart, M; Oro, D. 2016. When immigration mask threats: The rescue effect of a Scopoli’s shearwater colony in the Western Mediterranean as a case study. Biological Conservation, 198, 33–36. doi:10.1016/j.biocon.2016.03.034

Photo: M. Gomila

Abstract: Populations of long-lived species are highly sensitive to increases in mortality, but a loss of breeders can be compensated for by recruitment of local individuals or immigrants. Populations maintained through immigration can be sinks, jeopardizing the viability of the metapopulation in the long term when additive mortality from anthropogenic impacts occurs. Thus, the correct identification of whether a breeding population is maintained by local recruitment or by immigration is of special importance for conservation purposes. We developed robust population models to disentangle the importance of local recruitment and immigration in the dynamics of a Western Mediterranean population of Scopoli's shearwater Calonectris diomedea showing low adult survival but stable breeding numbers. Our results show that the shearwater population is not self-maintained but rescued by immigration: yearly immigrants recruiting in the population represents ~ 10–12% of total population size. We believe that this situation may be common to other Western Mediterranean populations, currently acting as sinks. We recommend urgent demographic studies at large core colonies to evaluate the global conservation status of the species.

 
A press release of the publication has just appeared. You can read the spanish version here