Bird populations aren't static, we are always hearing about the decline in House Sparrows and the increase in Little Egrets, there are other winners and losers that are common garden birds.
Collared Dove abundance has increased rapidly since the species first colonised Britain in 1955. From just four birds known to be present in that year, the population was put conservatively at 15,000–25,000 pairs by 1970. Since then the population has continued to rise, despite a temporary levelling out in the 1980's. There were about 300,000 pairs in 2000 and it has certainly increased since then.
On the other hand the abundance of breeding Starlings in the UK has fallen rapidly, particularly since the early 1980s, and especially in woodland. The species' UK conservation listing has been upgraded from amber to red as the decline has become more severe. The reasons are complex but in rural areas the reduction in the area of permanent pasture, their preferred feeding habitat appears to have been a cause. The population in 2000 was about 800,000 pairs and this had probably declined by about 35% since then. There has been a decline of over 80% in 45 years.