The Influence of Infrastructure on the Breeding Distribution of a Threatened Top Predator

The eastern imperial eagle (<i>Aquila heliaca</i>) has shown a marked population increase in the past decades in Hungary. The breeding range is expanding towards homogeneous agricultural habitats of the Hungarian Plain, where the already existing and recently growing infrastructural network is thought to be one of the main factors limiting distribution. We used data from 508 breeding attempts between 1989 and 2008 to assess the effects of infrastructural networks on breeding distribution. We constructed a single cumulative infrastructure effect (CIE) variable based on the avoidance of different infrastructure types by eagles in the past 20 years. Conditional autoregressive models were built in a Bayesian framework to quantify the effects of infrastructures on the spatial breeding pattern in a pre-defined core study area. Both multivariate and CIE models were able to classify the presence of breeding attempts with high accuracy. The CIE variable was used to build a predictive distribution model for the Hungarian Plain. The results suggest that infrastructure has a significant local effect but does not necessarily hinder the future range expansion of imperial eagles, as two-thirds of the prediction area seems to be suitable for the species. The methods and results described enable conservation managers and policy makers to assess the trade-off between infrastructural development and nature conservation priorities.