New publication on foraging range and colony size in seabirds

Jovani, R,; Lascells, B.; Garamszegi, L. Z.; Mavor, R.; Oro, D.Colony size and foraging range in seabirds. Oikos DOI: 10.1111/oik.02781

We tested “Ashmole’s halo” hypothesis of food depletion around colonies using a phylogenetic comparative study of 43 species of seabirds (28,262 colonies). We confirmed that foraging range imposes a ceiling on the maximum colony size of seabird species. 

Abstract:The reasons for variation in group size among animal species remain poorly understood. Using “Ashmole's halo” hypothesis of food depletion around colonies, we predict that foraging range imposes a ceiling on the maximum colony size of seabird species. We tested this with a phylogenetic comparative study of 43 species of seabirds (28,262 colonies), and investigated the interspecific correlation between colony size and foraging ranges. Foraging range showed weak relationships with the low percentiles of colony size of species, but the strength of the association increased for larger percentiles, peaking at the maximum colony sizes. To model constraints on the functional relationship between the focal traits, we applied a quantile regression based on maximum colony size. This showed that foraging range imposes a constraint to species' maximum colony sizes with a slope around 2. This second-order relationship is expected from the equation of the area of a circle. Thus, our large dataset and innovative statistical approach shows that foraging range imposes a ceiling on seabird colony sizes, providing strong support to the hypothesis that food availability is an important regulator of seabird populations.

You can read the philosophy behind “Colony size and foraging range in seabirds” in Oikos blog, by Roger Jovani

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.

Lizard October Campaign just started !!

The October campaign on capture-recapture of lizards just started with two new important discoveries:

1 - The "Imperial Sardines pincho"(c), a slice of bread with sardines on fresh tomatoe sauce, chopped garlic, parsley and Soy sauce. Freshly made and freshly served ! 
 



2-  The proof of elephant dwarfism on islands (we were not able to find any giant rat, though)


(...and as usual, we came back with quite a lot of rubbish washed on the island).
 

Congress: XVIII Italian Ornithological Congress

The GEP at the XVIII Italian Ornithological Congress at Caramanico Terme (PE) with a contribution on "Elements of bird populaiton management".
 
You can see the programm and download the congress abstracts here. 

Some pictures of the event here

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.

Ana Payo at NAUKAS BILBAO 2015: The big van theory

A new monologue by Ana Payo and Helena González from The Big Van Theory at NAUKAS BILBAO.

Nikola Matovic Master defense on streaming, now!

Nikola Matovic will defend his Master work on Storm petrel demographic parameters for the European Master Marine Environment and Resources today (09/09/2015). If you are interested you can follow his defense on streaming here