\(\phi_1\)corresponds to fledgling survival rates, \(\phi_2\)to adult survival rates and \(\rho_t\) to the mean fecundity in year \(t\). We considered that mean survival rates are constant across years, because we have no information to the contrary . To inform our estimates on adult survival rates we fitted an exponential survival curve to observations from \citet{Garcia_Heras_2019}, who confirmed 3 fatalities out of 13 tracked breeding birds (followed for an average of 365 days).  We added a fourth bird that was confirmed dead by RS but was not accounted for in  \citet{Garcia_Heras_2019}, although the addition of this fourth bird did not affect model results substantially. There is no information with regards to juvenile survival of Black Harriers, because of the poor return rate (six birds) from 465 ringed harriers in the national ringing scheme \citep{SAFRING2020}. Thus, we simply assumed lower survival rates for birds in their first year than older birds, as found for other species of harriers from Europe \citep{Arroyo_2002,Etheridge_1997,Newton_2016}.