Selección de hábitat del picamaderos negro en el Parque Natural de Aiako Harria
Auteurs : Robles (Hugo), Ciudad (Carlos) et Porro (Zeno)
Année de publication : 2020
Publication : Rapport d'étude Habios, CTFC, Interreg Poctefa
Résumé :
Within the framework of the project Interreg POCTEFA – Habios, we studied habitat use and selection of black woodpeckers by transects in the (pre)breeding period and through telemetry by radio-tracking 13 juveniles after fledging in the Aiako Harria Natural Park (Guipuzkoa). While adult woodpeckers preferred relatively old forest (‘fustales’) with high canopy cover, juveniles did not prefer structurally ‘mature’ forests. However, juveniles used also mainly fustales (>80% of observations) with high values of canopy cover (>80%) in the pre-exploratory period as well as during the exploratory dispersal period farther away from the natal range. Nevertheless, we did not find a predominant use of any given forest type, neither in juveniles nor in adults. The use of an ample array of vegetation types(defined according to the dominant species) suggests that these woodpeckers may exhibit some flexibility in habitat use. Consequently, forest management strategies should focus on favouring the maturity of the woodlands andtree plantations, both broadleaved forests (mainly beech and oak forests) that may provide breeding cavities and food, as well as conifer plantations (Pinus nigra, P. radiata, larch, Douglas fir, European spruce) to provide food for breeding adults and postfledging juveniles during the dependence and dispersal periods. The minimum apparent survival of the juveniles during the first six months after fledging varied from 7.7% to 46.2% depending on data treatment. While these results match the high juvenile mortality observed for other birds, the low sample size in this study prevents us from making strong inferences. Thirteen juveniles during the preexploratory period moved considerably shorter distances that the two sisters that survived to the more exploratory (dispersal) period, which led these sisters to move several kilometres away from the natal nest (movements even higher than 7 km between consecutive locations and 5 km from the natal nest) from the beginning of dispersal at the end of August. Because of the small sample sizes, the low body mass of the juveniles (210-265 g), the female-biased sex ratio (females are lighter than males), the low number of chicks per nest (average of 2.1) and the low juvenile survival are demographic parameters that require further monitoring to understand their influence on the population dynamics of black woodpeckers in Aiako Harria. Anyway, the high mobility of the juveniles and the low abundance of breeding territories suggest that the conservation of black woodpeckers at the population level may require from management units considerably larger than the Aiako Harria Natural Park. This would allow, among other things, the arrival of immigrants that may favour the renovation of the population within the Natural Park. With the aim of improving our knowledge on habitat use and selection, and according to previous results, we recommend the following research lines: - To keep and extend the system of transects designed in Aiako Harria to other areas in the Basque Country to monitor population dynamics and to evaluate potential changes in breeding habitat use of woodpeckers in relation to changes in forest management practices at mid and long term. Moreover, this would allow to increase considerably our knowledge on habitat use and selection through the comparison of the results in Aiako Harria with those in other more homogeneous environments. - Use of high-precision telemetry to track (pre)breeding adults and postfledging juveniles. However, it should be mentioned that the current technology does not allow tracking small/medium-sized birds, such as woodpeckers, with the spatial and temporal accuracy required to monitor the movements of these birds in detail. This is partly due to the high error of GPS devices in mountainous and forested areas, which is even more conspicuous if we take into account that the low battery size does not allow the devices to be connected long enough as to increase the accuracy of the locations.