Relationship between trends in abundance, land use changes and nest protection: the Montagu's Harrier in Spain

Abstract

Montagu’s Harrier is a steppeland raptor, whose populations in Spain (a stronghold of the species in the EU) and elsewhere in Europe are affected by agricultural management modifications supported by CAP policies in the last decades. With lineal mixed models (including province nested within autonomous community as a random term) we try to relate the population changes between 2006 and 2017 at UTM cell level with modifications of area occupied by different farmland land uses, the extension of protection campaigns to protect nestlings at harvest time, and the levels of risk that harvest activities pose to harriers there (based on harvest dates). Overall, we found a net loss of breeding pairs in the 410 UTM cells monitored both years, as well as a net loss of pastures/dehesas, and a net increase in woody crops. We did not find significant relationships with any explanatory variable on Montagu’s Harrier population changes, but changes in woody permanent crops area approached significance (p=0.08), with more pairs being lost in areas where woody crops had increased the most. Also, and although differences were not significant, there was a trend for bigger population losses of this raptor in areas with no protection, which suggest that protection measurements may reduce the population drop, but its efficacy may be diminished under land use changes.