Although thousands of wild birds each year have bands attached to their legs to plot their travels, only a tiny fraction of these are recovered.
But when they do turn up they can reveal some remarkable statistics.
One banding success story concerns a Tasmanian silver gull straying far from home to reach Queensland. Not only that, the gull has broken records for the longevity of the species. It was found to be at least 29 years old.
The story of the silver gull starts on Spectacle Island in Frederick Henry Bay in December 1988 when it was banded by the late Bill Wakefield, who assessed the bird to be about two years old.
Nearly 30 years passed before the gull was discovered ensnared in fishing line in Brisbane.
Each band has a serial number recording age and place of banding and details are recorded by the Australian Bird and Bat Banding Scheme. So precise is the banding process that the place of recovery was actually given as Stanley St, South Brisbane.
After rescue, the bird was sent to a wildlife rehabilitation centre for a health check before being released. The band was left in place.
Although rescued two years ago, a full account of bird’s history has only recently reached ornithologist Els Wakefield, who has continued her late husband’s work on gull research and conservation.
The previous record for a log-lived silver gull was 28 years, even though life expectancy of the smaller gulls is about 15 years. The bigger species – including the kelp and Pacific gulls also found in Tasmania – live longer, possibly 30 years. The oldest record for a gull is a herring gull which attained an age of 59 years in Britain.
The banding of birds not only gives an indication of life expectancy and reasons for mortality, it also helps scientists understand patterns of migration, and the limits of individual journeys.
Banding is especially important for the study of migratory species but it can also shed light on resident birds, like the silver gull which is not a migrant and does not normally travel great distances.
Gull research in recent years has not been about far-distant movement, but gulls’ breeding success.
Because they tend to live in an urban environment, gulls have a “canary in the coalmine” role, signalling poisons and pollution in the environment which can harm humans.
Gulls can also teach us about our own health. Urban gulls – because they largely feed on human junk food at fast-food outlets and on rubbish tips – have been found to have many of the ailments which afflict unhealthy humans, like obesity and high cholesterol levels.
I’m informed, though, that the silver gull trekking to Queensland looked healthy enough, despite its entanglement. It appeared to be eschewing the Sunshine State’s rubbish tips for a feed of fresh fish along the Brisbane River.