G.E.P. at the Percy FitzPatrick Institute & SEEC

Ana Payo-Payo, from the GEP, has visited the Percy FitzPatrick Institute of African Ornithology  and the Centre for Statistics in Ecology, the Environment and Conservation (SEEC) at Cape Town (South Africa) with a fellowship from the Spanish Ministry of Education. During the 2-month visit at the FitzPatrick and SEEC Ana explored SouthAfrican wildlife and worked with Prof. P. Ryan and Prof. R. Altwegg on the application of multievent and state-space models on seabird populations.

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

G.E.P. at the Simon Fraser University

Artwork by G. Smith, 1965

G. Tavecchia, from the GEP, is visiting the Simon Fraser University at Burnaby Mountain (Canada) with a fellowship from the Spanish Ministry of Education.  
During the 3-months at SFU he will work with Prof. C. Schwarz on an application of site-occupancy models.

Summering in Eastern Spain

The three Yellow Legged Gulls equipped with GPS-GSM in Mallorca at the beginning of this summer decided to spend the summer in different places. As many tourists, however, they chose to spend the summer in North-Eastern Spain. One (green cyrcle) moved up to Zaragoza, a second one stayed in Mallorca (blue cyrcle) and a third spent the summer near Barcelona (red cyrcle). 

Soon will be time to decide where to spend the winter ..?! 

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.

Scopoli's Shearwaters: new press release and radio interview !

Photo Ana Sanz-Aguilar

A new press release on the two last work on Scopoli Shearwaer by the G.E.P. appeared this week at "B@leòpolis" the scientific suplement of "El Mundo" (Balearic version). You can read the full note here (in Spanish).

J.-M. Igual (GEP) and M. McMinn on Shearwater management actions at "Balears Fa Ciència" is here (from 10').