Concerns have been raised over the "grim" sight of dead birds massed in nets attached to the Runcorn-Widnes bridge.
Alarmed residents believe the birds have died after becoming trapped on Mersey Road in Runcorn
Some of the birds still appeared to be caught up in the netting on Monday.
Ryan Waterfield, 37, of Runcorn, is among those to have complained to the council over the creatures' plight, which he said includes pigeons with their necks or heads tangled.
He believes the nets are a hazard even when well maintained with gaps that are not supposed to be big enough to let birds through.
He described the sight of dead birds "hanging there" as "quite grim", and he called on Halton Borough Council to adopt a policy he was aware of in Chester of having no nets.
As well as under the Silver Jubilee Bridge, better known as the Runcorn-Widnes bridge or Runcorn bridge, he said there are problems at Top Locks on High Street and near Runcorn Station.
He said the RSPCA told him there have been issues for years in the area.
Halton Council said the nets are designed to keep birds out to stop their droppings from presenting a hazard to bridge workers and the public, and from damaging the bridge paint.
It said vandalism is the most likely reason for holes being cut in the nets.
A council spokeswoman said reports from the public this last week prompted the local authority to send a cherry-picker to the scene to cut any trapped birds free, but that no trapped birds were seen when the nets were inspected.
The RSPCA said it had conducted several visits and although living birds were behind the nets, they were not trapped and could fly out.
An RSPCA spokeswoman said the charity receives around 2,000 reports of birds trapped in nets every year, and damaged bird-deterrent netting is a "major cause".
Creatures unable to find their way out face a "long and painful death".
She said: "There were some dead birds in the netting but it appears that they have been there for some time.
"We have contacted the local authority and have raised our concerns with them and hope they will help rectify the issue, in the meantime we will continue to monitor the situation.
"These birds can suffer a long and painful death from injury or starvation.
"Unfortunately bird-deterrent netting is often fixed in high or hard-to-reach areas, making the rescue of trapped animals difficult and dangerous."
The Halton Council spokeswoman said: "The netting was installed to keep pigeons out of the structures.
"This is important because their droppings are a hazard to staff carrying out bridge inspections and maintenance work, and the council has received complaints about droppings accumulating on footpaths and presenting a hygiene risk to pedestrians.
"The droppings also degrade the protective paint systems on structural steelwork.
"If pigeons are not prevented from roosting or nesting on structures, their droppings must be removed before routine inspection or maintenance work can be started.
"The netting systems used are robust, but cannot be completely vandal-proof, and it is generally vandalism that leads to pigeons getting back under the structures.
"This is what we believe has happened at the bridges in question.
"We received information on Thursday that pigeons were tangled in the mesh.
"As a result, we immediately sent a contractor with (a) ‘cherry-picker’ to the site with instructions to cut the netting in order to free any tangled birds.
"They attended the site and cut the mesh in several places, although they didn’t see any birds that were tangled up.
"They returned on Friday morning, and there we no tangled birds.
"While the sight of dead birds in netting is very unpleasant, it can’t be assumed that those that have been seen had been tangled in the netting.
"We rarely receive reports of tangled birds, and the pigeons under the structures adjacent to Top Locks car park are not ‘trapped’ as they can come and go via holes that they have found in the netting.
"We will review the provision and maintenance of netting on structures in the near future."
Mr Waterfield said: "There’s still the issue of them becoming entangled.
"Some seem to be caught by the neck and the head.
"I still think it’s a problem.
"People look up and see them hanging there."
Sightings of trapped birds should be emailed to [email protected] including the address, property owner if known and date.
For more information visit www.rspca.org.uk