Milder winter temperatures in Europe and bumper fruit crops in the country have seen fewer birds in gardens, RSPB Cymru have claimed.
The house sparrow was the most seen bird in Welsh gardens
The bird charity's Big Garden Birdwatch results have shown smaller numbers of birds visiting backyards in Wales.
Bird numbers are usually swollen by seasonal migrants but RSPB Cymru said above average temperatures across Europe have kept them on the continent.
Blackbirds and robins were recorded at lower levels than in previous years.
More than 21,000 people in Wales took part in the RSPB's UK-wide Big Garden Birdwatch over the last weekend in January, and participants counted the birds in their gardens.
One of their findings was an overall decrease in the number of resident birds.
TOP SPECIES IN WALES
Average per garden
Blue tit: 4.02
Great tit: 1.61
Collared dove: 1.34
Greenfinches dropped out of Big Garden Birdwatch top ten in Wales, with a decline of more than a quarter since 2006.
Although the house sparrow retained its top spot with an average of 5.77 per garden, its numbers were significantly down from the first birdwatch in 1979.
The starling moved back into second place and the blue tit completed the Welsh top three, with average numbers of 4.51 and 4.02 per garden respectively.
Peter Jones, RSPB Cymru's Environmental Policy Officer, said the varying bird numbers visiting Welsh gardens was one example of the impact climate change was having on the natural world.
"As our climate changes the distribution of birds will change and they will adapt their behaviour," he said.
"Although the mild winter seems to have provided more food for songbirds in the countryside this year, as changes to our climate become more extreme, many birds will struggle to cope with the altered weather patterns.
"We can all help to minimise the impact of climate change by the action we take in our everyday lives."