In addition, we used the model proposed by Collingham et al. (2014) to estimate adult survival of Southern African birds with insufficient ring returns based on demographic and ecological factors derived from South African birds (n = 67) with robust survival estimates. Survival estimates can be estimated from the model: 
\(\text{logit}(\phi) = 0.5419 + 0.1595 \ log(\text{mass}) - 0.7246 \ log(\text{clutch})\)
where \(\phi\) is expected adult survival mass refers to mean body mass is in grams and  clutch is mean clutch size.
Given that the mass of adult female Black Harriers average  525  + 43 g (n = 33) and adult males average 387 + 26 g (n = 17) (RE Simmons, M-S Garcia-Heras unpubl data)  and clutch size averages   3.58 ± 0.64 (n = 183:  Garcia-Heras et al. 2017b), adult survival is  calculated as 0.72 (females) and 0.73 (males) after Collingham et al. (2014).