WWT Washington Wetland Centre has sighted 16 adults and 21 young this year, in comparison to 23 adult birds last year.
They have nested by a lake and shingle island which expanded by the centre last autumn. Breeding at the site started in 2006.
Reserve manager John Gowland said it was a "real conservation success story".
"The high number of youngsters is a positive sign on the success of the improved shingle islands and emphasises the growing confidence of the nesting adults," he said.
The birds, which are a rare on Wearside, were once declared an extinct breeding species in the UK.
The avocet returned in the 1940s and is the emblem of the RSPB.

Laura Beal has served with the Devon and Cornwall force for 13 years as a police constable and even featured in a force advertising campaign.
In her letter she says inadequate staffing has made it "impossible to do her job to the best of her ability".
It comes as inspectors warn police cuts are putting the public at risk.
Speaking to the BBC, Ms Beal said she was prompted to put her resignation letter on Facebook after her sergeant told her it was unlikely to be seen by the Chief Constable, Shaun Sawyer.
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She said she followed her father into the police when she was 19 and had always been proud to say she was a PC, but now felt "embarrassed at the way everyone is being treated".
In her letter she claims she was expected to go on patrol covering Mid Devon with one other officer most days.
"This is meant to be adequate and safe. How this can be acceptable is beyond belief," she wrote.
Ms Beal's resignation comes as the police standards watchdog warned some forces are putting the public at risk by rationing responses as they struggle with cutbacks.
Her Majesty's Inspectorate of Constabulary said some forces had "downgraded" 999 calls, in order to justify responding to them more slowly.
Its report found most of the 43 forces in England and Wales were providing a good service. But that others have let victims down.
Ms Beale said the job had left her suffering from stress and anxiety.
"Your staff are not coping, and are suffering because there is no one looking out for them.
"Front line response is where you need to focus your time and money. This is where the buck stops," she added.
Ch Supt Jim Colwell said: "I would like to formally thank PC Beal for her loyal service, hearing of an officer resigning is sad, particularly when this is done so publicly.
"We do hear concerns from officers and staff and recognise where they are feeling the strain.
"Being a police officer is not easy. It requires skills and personal resilience which are often unique to the role. We are a supportive force and will always assist an officer needing help or guidance."
Last month Devon and Cornwall Police announced it would be employing nearly 100 additional police officers into local policing in an effort to relieve pressure on frontline staff.
A wildfowl centre has recorded its highest number of rare avocet birds.
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A police officer has published a damning resignation letter on social media criticising police for "putting their employees last".