This is Scientific American 60 Second Science. I'm Emily Schweng. Urban development is encroaching on forests in the Pacific Northwest, and it's also ruining Valentine's Day for some songbirds.

Because urban growth is making it a challenge for some birds like the Pacific Wren to stay faithful to their partners at least in Seattle.

A housing boom is taking over the Wrens habitat, the thick forest understory.

So I really think it's just the fact that we kind of pull the rug out from underneath these birds, take

their forest away.

John Marzliff, Professor of Wildlife Science at the University of Washington.

While birds like crows and sparrows adapt well to human habitats,

Marslove says that development is forcing the Wren and other songbird species

to find new digs and when that run moves it also abandons its mate.

The work is in the journal Ploss 1.

Marslift's decade long study looks at six species in landscapes undergoing various levels of development.

If you don't go out for many years and follow individually marked birds, you'll never really understand

how nesting success over an animal's lifetime or

their strategies of moving and divorcing and finding new partners and places plays out over

their lifetime.

The study shows that even after birds re-establish themselves elsewhere,

they have a harder time laying eggs and rearing chicks than they used to.

More careful planning to let small urban forests remain

could help even the smallest bird species thrive in cities.

These are not huge areas again in the suburban matrix.

They're you know areas of 30 to 150 acres and

they are relatively easy to to set aside for birds like this.

...