Factors prevailing distribution of Eurasian Pygmy Owl and setting conservation priorities in Latvia

Abstract

Knowledge of species geographic distribution is of a critical value in conservation biology as it reflects the distribution of its realized ecological niche - the habitat preferences and requirements for survival. In this study we modelled the distribution of Eurasian Pygmy Owl in Latvia to set conservation priorities and evaluate the effectiveness of existing specially protected area (SPA) network for this species. We used MaxEnt to analyse the countrywide species distribution over a set of 34 ecologically meaningful factors describing different landscape and habitat classes, forest types, ages, dominant tree species as well as time since forestry disturbances etc. Analysis was conducted at 25 ha cell resolution using within-cell statistics as well as various landscape statistics of 490 ha and 1960 ha surroundings. The resulting habitat suitability map was used as input for zonation to set conservation priorities and to evaluate the importance of existing SPA network. The most important negative contributing factor in the model was the amount of agricultural lands while forests of at least five-meter height and the total area of old-growth conifer and mixed forests in 490 ha surroundings were positive. Spruce was the preferred tree species, and the age of the oldest forest patch within the analysis cell was a better predictor than the average forest age. Time since the last forestry disturbance was an important contributing factor as well. Our findings of landscape features in 490 ha and up to 1960 ha surroundings are consistent with previous knowledge of species breeding territory size1 and highlight the importance of 80-490 ha protection zone for territory. According to zonation analysis, priority 2% of the land territory hold 10% of the assumed population, 10% of the land hold 38% of the assumed population and 25% of the land hold 70% of the assumed population. A third of the assumed population is located in just 8% of the land territory, and by protection of this, the species extinction risk is estimated at 24%. From these most important sites, 23% may be considered as protected (9% by full forestry restrictions and 14% by partial, but possibly effective restrictions), 15% are protected with mostly seasonal forestry restrictions and 62% have no legal protection. In total, specially protected areas currently hold 17% of the assumed species population. We prove Eurasian Pygmy Owl to be an old growth forest specialist and conclude, that the specific conservation sites (micro-reserves) for this species should be established at larger areas than the current national legislation allows, and that Natura 2000 site network alone is not sufficient for protection of this species. 1. Strom, H. & Sonerud, G. A. Home range and habitat selection in the Pygmy Owl Glaucidium passerinum. Ornis Fennica 78, 145–158 (2001).