Martin City

Yesterday we went to the monthly meeting of the Yolo Audubon Society where there was a talk about purple martin colonies in Sacramento. It’s a fascinating story of adaptation of wildlife to the human landscape. The population of purple martins in the Central Valley of California crashed in the 1960s concomitant with the invasion of the European starling into the state. (Starlings were first introduced into the United States in 1890 by the most misguided Shakespeare fan ever: out of desire to see all the birds mentioned in Shakespeare’s plays this person released 100 starlings into Central Park in New York. The rest is ecological history.) Purple martins are cavity-nesters, as are starlings, and the starlings are able to aggressively boot the martins out of nest sites.

The population of purple martins in Sacramento hung on, however. Prior to the starling range expansion, the martins were already nesting in curved roof tiles on the top of various city buildings. What the martins then did was to start nesting in holes on the undersides of elevated highway structures. These weep holes lead to hollow chambers inside these long highway bridges where the martins build their nests. Martins are much better flyers than starlings and have an easier time flying up into these weep holes so the martins have ended up with a refuge where they can raise their chicks.

Sacramento is now the only place in the Central Valley where purple martins breed. The population in the city is increasing very slowly and is now at about 150 pairs. Whether the birds will be able to expand their range outside of Sacramento by nesting under highways isn’t known, though last year a pair did nest here in Davis at a road overpass near the Sudwerks Brew Pub on the east side of town.