Population Trends and Multi-Scale Breeding Habitat Analysis for the Black Stork (Ciconia nigra) in Dadia-Lefkimi-Soufli National Park, North-Eastern Greece

Abstract

Aims: The aim of the study was to assess Black stork (Ciconia nigra) population trends and breeding habitat preferences in two habitat scales, in the National Park of Dadia-Lefkimi-Soufli (Dadia NP), in north-eastern Greece. Dadia NP is a renowned European biodiversity hot-spot (N 40° 59' to N 41° 15', E 26° 19' to E 26° 36'). Study Design: The Black stork breeding population was monitored under the Systematic Raptor Monitoring Scheme (SRM), which was established in the area by World Wildlife Fund (WWF) Greece. Place and Duration of Study: The study was conducted in Dadia NP with annual monitoring efforts from 2001 until 2006, and once again in 2012. Methodology: Twenty-four vantage points and ten road transects were selected throughout the entire study area. All Black stork individuals were surveyed and mapped during five months (March to July), for each monitoring year. Nesting habitat was measured in two scales. To assess the microhabitat, nesting-trees and vegetation variables were measured in a circular area of 0.1 ha (radius 17.85 m) around each nest. For the macro-habitat scale, a total of ten environmental variables were analyzed to model habitat suitability. MaxEnt software was used using high spatial resolution satellite data for each monitoring year. Results: Black stork territories increased in Dadia NP from 24 pairs in 2001 to 33 pairs in 2012 demonstrating a total of 34.7% relative increase. According to Man Kendal tests, the species had a positive MK slope (1.7) which although not significant (tau = 0.69, P = 0.08), denoted a continuous increase. Increasing trends were corroborated by GAM models. The Black stork generally used large mature trees for nesting in sparse forests patches. The variable “elevation” demonstrated the most useful information for habitat modeling. During all monitoring years, Black stork showed a clear preference for the lowlands close to arable fields and wetlands which were used for foraging. Following the positive trend of Black stork population, the species’ suitable nesting habitat also extended from 48% in 2001 to 72% in 2012.