The conservation charity the Wildfowl & Wetlands Trust increased its income by 7 per cent last year, according to accounts published this week.
The accounts, for the year to the end of March, reveal that the charity's income grew from £22.4m in 2016/17 to £24m last year.
Legacy income more than doubled from £1.7m to £3.6m, membership income rose by 2 per cent to £7.1m and investment income grew by £0.5m.
But contract income declined from £2.1m to £1.5m.
The trust also received a £4.1m Heritage Lottery Fund grant towards a three-year £6m project at its Slimbridge Wetland Centre in Gloucestershire to celebrate the life of Sir Peter Scott, who founded the charity in 1946.
Expenditure at the trust, whose patron is Prince Charles and whose vice-presidents include Sir David Attenborough, increased from £23m to £23.7m.
The number of full-time-equivalent staff went up from 418 to 430. Total wages rose from £10.2m to £10.6m, which included £49,000 of severance payments.
The highest earner was in the £110,000 to £120,000 pay bracket – the same as the previous year.
The accounts say "pay and market conditions continue to be a challenge".
And a section on the gender pay gap says: "Although we have a gap, we are not out of kilter with the charity sector."
Nobody at the charity was available to comment on the accounts on Wednesday morning.