In the latest incident, a man escaped with a three-figure sum after threatening two members of staff with a hammer at McColl's in West Doura Court, Kilwinning, at about 18:20 on Saturday.
Police said the staff were uninjured but "extremely distressed".
In December, a man robbed the same shop at knifepoint while wearing a 'Joker' mask.
The suspect in the latest robbery was described as being white, 5ft 10in, with a stocky build. He was wearing dark trousers and a black hooded top featuring the "McKenzie" logo.
Det Sgt Craig Semple said: "I'd like to speak to anyone who may have seen the suspect hanging around the area prior to the robbery taking place or anyone who saw him running out of the shop afterwards."The first bird emerged at the Cors Dyfi reserve near Machynlleth on Friday, followed by a second on Sunday.
The eggs were laid six weeks later than usual leading to concerns over whether the chicks would hatch.
Parents Monty and Glesni set up home on a 30ft (9m) tall man-made nest on 3 May.
They are one of only two known breeding pairs in Wales, with a second pair nesting near Croesor in the Glaslyn Valley.
Staff and volunteers at the Cors Dyfi nature reserve had an anxious wait for the chicks who took 32 hours to emerge from their shells.
Cracks in the first egg were spotted on Friday afternoon, with the bird finally hatching at about 21:00 BST.
The second chick started chipping away from inside its egg on Saturday afternoon but did not hatch until 20:40 BST on Sunday.
Monty and Glesni became a breeding pair for the first time this year after Monty's previous partner of two years, Nora, did not return from her African migration.
Ospreys return from migration in late March or April and usually lay eggs two or three weeks later.
But Monty and Glesni did not pair until 3 May and their two eggs were laid between 22 and 25 May - six weeks later than average.
Alwyn Evans, of Montgomeryshire Wildlife Trust, said: "By the time Monty finally paired off with his new partner, Glesni, a three-year-old bird from Rutland Water, it was getting late in the season.
"At that stage none of us knew if they would lay eggs, let alone whether they would hatch.
"It's been an emotional weekend to say the least."
Mr Evans said cracks in the second egg on Saturday were greeted with loud applause and shouting from visitors at the wildlife trust's osprey centre who had gathered to watch the birds hatch.
Last month the wildlife trust said ospreys were still persecuted and egg collecting remained a problem in the UK.
To protect the Powys eggs, more than 50 trust volunteers have worked 1,300 hours to ensure the nest has been watched 24 hours a day during the six-week incubation period.
The first osprey chick in the Dyfi valley for 400 years hatched in 2011.
Once prolific birds of prey in the UK, their numbers were drastically reduced in the 1840s after years of persecution, including egg collecting, hunting, taxidermy and loss of habitat.
The Dyfi Osprey Project has been popular with tourists, with an average of about 30,000 people visiting the nesting site annually.Officers say the 18-year-old suffered an adverse reaction and later died, after taking MDMA at The Warehouse in Byker, early on Sunday.
A 19-year-old man was arrested shortly afterwards and another two men aged 19 and 21 were arrested on Monday.
Both 19-year-olds have been released on bail, while the 21-year-old remains in custody.
All three were arrested on suspicion of supplying a controlled drug.
Police have urged anyone who was at the venue on Saturday night and took drugs to see a doctor.
MDMA forms the active ingredient in ecstasy pills.And the Ibrox boss is amazed the word "crisis" is being used in the media.
"We've played 14, drawn one, lost one - if that's a crisis then there's a crisis in football," said Warburton.
"At the start teams saw how we play, it's quite natural then to put eight, nine, 10 men behind the ball - teams will do what they have to do to win."
He added:  "That's not a criticism, but we have to deal with it and it's tough to break down compact, solid defences of that number of men."
Despite winning their first 10 Scottish Championship matches, their run was broken by Hibernian at the start of this month when they lost 2-1 at