Paul Ronalds was presenting virtually at an event hosted by New Zealand's Council for International Development.
He said Covid-19 will be a true test of whether NGOs can make the necessary changes to fit the new strategic environment.
Mr Ronalds said charities that are prepared and able to undertake significant change will survive.
He said the virus has accelerated existing trends that were already putting pressure on aid charities, "the business model was already broken…In most countries, there is simply too many NGOs, chasing too few dollars."
At the same time, public donations are likely to drop due to the virus.
Mr Ronalds said charities need evidence of the impact they have and tell this story to the public.
He also advocated the use of digital technology to save money and to embrace direct funding of local community organisations.