Llyn Brenig have ringed and named the single female osprey chick there. She's called Luned and weighed 1.770 Kg.
So we know three female osprey chicks are over 1.7 Kg (two at Dyfi, one at Llyn Brenig) and to quote Glaslyn "the two females came in well above 1.5Kg which is the maximum if the scale which means they are all a good healthy weight. The two males, one at Glaslyn and one at Dyfi weighed 1.460Kg and 1.410 Kg respectively, so yes Marigold, the males are smaller than the females.