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').

Spring 2016 campaign on Lilford's lizard ended!

The 2016 spring campaign on Lilford's lizard ended last week. It has been a difficult one, with many days of bad weather and several unexpected problems with boat and logisitc....but hey, this is job. Populations reached a very low level, but it seems there will be many new recruits in October. Thank to the many people from the GEP who gave their help.

First long tracks from Dragonera

The GSM/GPS devices are sending interesting information on bird movements. Marked gulls seem to have moved their core area northward, between the delta of the river Llobregat and the landfill, north of Barcelona city.

The YLG 2016 campaign ended !

Photo: J. Bos

The 2016 Yellow-legged gull campaign at Dragonera Natural Park ended after a survey, egg measuring, birds' trapping and marking.
  

Photo G. Tavecchia:  A gull equipped with a GSM/GPS device

Thanks to T. Muñoz, of the G.O.B., who helped us to equip four birds with a GSM/GPS device to investigate their feeding strategy.

Photo J. Bos.

Photo J. Bos: A gull defending its nest

  

Gulls use to attack intruders, especially near the hatching period. It is a good occasion to make some pictures and read the ring. 

Can you read the ring code?

Photo J. Bos: Gulls behind a trawler

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

Stage at the G.E.P.

Julia Bos joined the GEP for her Erasmus+  stage.  She will be investigating the within-colony differences in egg volume, clutch size, movements and spatial structure of the Yellow Legged Gull at Dragonera Island. Welcome Julia.