The TV broadcaster said some of the UK's most common species have suffered "significant declines" in recent years.
Many have experienced "several poor years", he added, due to cold weather and with their habitats under threat.
Warm weather this year has given some species, such as the meadow brown and red admiral "a good start", he said.
More than three quarters of the UK's butterflies have declined in the last 40 years, with numbers falling quicker in towns and cities, experts say.
Sir David, president of Butterfly Conservation, said that despite a warm summer last year, species like the small tortoiseshell, peacock, meadow brown and gatekeeper had seen numbers fall due to a warm winter and a subsequent cold spring.
"Worryingly, we are now seeing the fortunes of some of our once common butterflies mirror those of our rarest species and they too are now also suffering significant declines with butterflies declining more rapidly in urban areas than in the countryside," Sir David added.
"In the last decade our butterflies have experienced several poor years and although resilient, they simply cannot sustain repeated losses, especially if the habitats they need in order to rebuild their populations are also under threat."
He said 2017 has been a good year for species so far, but added: "Butterflies really need this to continue."
Sir David urged members of the public to take part in the annual Big Butterfly Count to see if common species can bounce back this year.

The $620m (Â£395m) he made before tax means he has topped Forbes' list of the biggest earners in music in 2014.
Not only that, but he has now also got the Forbes record for the highest earnings in a single year by any musician.
The majority of his cash has come not from record sales but from Apple's purchase of Beats, the company he founded, for $3bn (Â£1.9bn).
Best known for their headphone range, Beats also makes technology used in car audio systems and has a music streaming service known as Beats Music.
Priced about $300 (Â£191) in the US, Dr Dre, if he were so inclined, could buy more than two million sets of his Studio headphones with his earnings.
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One pilot died and another jumped clear as the helicopter crashed during an aerobatic display by the elite Berkut squadron in the Ryazan region, about 170km (105 miles) south-east of Moscow.
The Russian military has blamed the crash on a hydraulics failure.
There have been six other Russian air force crashes in recent weeks.
The two-seat gunship was performing stunts and firing flares with three other helicopters. It then began to spin rapidly, before falling to the ground and bursting into flames.
Its pilot Lt Col Igor Butenko was killed. His son told Russian media that the accident was not due to pilot error.
"There are situations when it's impossible to survive no matter how well-trained the pilot is," he told Lifenews.
The Russian defence ministry says the condition of the other pilot's condition is "satisfactory".
There were no injuries to spectators at the air show.
An investigation has been launched into the cause of the crash, although the surviving pilot has said that a hydraulic failure was the cause. The country's fleet of Mi-28s will remain grounded until the investigation is completed.
The Mi-28 is an attack helicopter widely used in Russia, as well as countries such as Iraq and Kenya.
At least five people have been killed in recent military aviation crashes.
In the past few years, the air force has received hundreds of new helicopter and planes as part of a programme to modernise and reequip Russia's military.
Butterflies in the UK are facing "a vital" period following a worrying decline in their numbers, naturalist Sir David Attenborough has warned.
[NEXT_CONCEPT]
Dr Dre has taken home an enormous amount of money this year.
[NEXT_CONCEPT]
The Russian defence ministry has grounded its fleet of Mi-28 attack helicopters after a fatal accident at an air show on Sunday.