Bird lifespans vary by habitat and size

How long do birds live? With luck, a surprisingly long time for such small creatures.

Near the low end for local birds, house wrens and hummingbirds can live nine years. Bluebirds, some warbler species, orioles and downy woodpeckers can live 10 to 11 years. Crows can live 14, house sparrows, 15, and mourning doves are near the top of the back-yard list at 31 years.

The fuller answer to how long birds live: It depends. For answers about which birds live long and under what circumstances, I turned to several research papers I found on the Internet. The papers contain extremely complex discussions of biology, most of which escaped me, and which we will not discuss in detail.

But in general:

Birds live longer than non-flying animals of similar body size, up to three times as long. A chickadee, on average, outlives a shrew or mouse of similar size. (Aside: But not a bat of similar size. Bats, like birds, live longer than non-flying mammals of their size. There is record of a 7-gram bat living 41 years. Seven grams is half an ounce. That's what a warbler weighs. Warblers would be extremely lucky to live 41 months.)

Larger birds live longer than smaller birds. An albatross can live much, much longer than a chickadee. But size isn't an absolute determining factor, as a smaller chickadee will live longer than a larger chickadee.

Basically, both birds and bats have evolved to reduce the accumulation of harmful metabolic substances in their bodies. You and I this very moment are suffering from oxidation of cells and DNA. We're rusting. Birds and bats rust more slowly in comparison.

Communal roosting — often done by crows — also helps extend life. As does slower maturation. Bluebirds are out of the nest and on their own in less than a month. Bluebirds die young. Young crows often stay with a family group for a year or two following hatch. Young crows get more attention, care and learning opportunities.

Birds that live in colonies live longer than birds that nest individually. This might be related in part to a larger number of eyes watching for predators.

Birds that migrate live longer than birds that don't. A few months in the tropics pays off. Generally speaking, birds that live in the tropics live longer than birds that don't.

It isn't easy to be exact on how long birds live. Banding — attaching a tiny metal band to a bird's leg with an assigned number — is the only way wild birds' age can be accurately determined. When the bird dies, if the band is recovered, dates of banding and recovery provide an age.

If you were a bird and wanted to live a long time, you should go to sea. The bird-banding database lists species with the longest documented lives. The top 10 are Laysan albatross, black-footed albatross, great frigatebird, white tern, sooty tern, wandering albatross, Arctic tern, red-tailed tropicbird, black-browed albatross and Atlantic puffin, which brings up the rear at 31 years.

Lifelong birder Jim Williams can be reached at woodduck38@gmail.com. Join his conversation about birds at www.startribune.com/wingnut.