Complex sentence: Whilst he was in Finland in 1858 he discovered breeding Waxwings and was the first English person to collect their eggs bringing fame among English ornithologists, most of whom were egg and skin collectors.
Split into simpler sentences: Whilst he was in Finland in 1858 he discovered breeding Waxwings and was the first English person to collect their eggs. This brought him fame among English ornithologists, most of whom were egg and skin collectors.