Vagrancy and the Urban Landscape
Southern California is a hotbed of avian vagrancy – large numbers of rare birds, especially passerines such as warblers, sparrows, and flycatchers, originating largely from Eastern North America, appear in the region in fall, and many stay throughout the winter. These vagrants offer an outstanding opportunity to look at the habitat value of the urban landscape from a different perspective – while we know native plants are the basis of native avian life, do they offer the same benefits to these transcontinental visitors, or do vagrants prefer plants that they may find in their original range?
The perhaps-surprising answer? Vagrants almost uniformly prefer California Natives – particularly Coast Live Oak and California Sycamore, our two most important native trees – to plants that they are familiar with and are likely abundant throughout their original range. Southern Magnolias are widely planted across our region as ornamentals, for instance – but magnolias almost never harbor vagrant birds, even species from the southeast like Yellow-throated Warblers or White-eyed Vireos. Not only do vagrants have a preference for native trees, though, but they stick around in them for much longer. While non-native ornamental trees such as jacarandas often attract “one-day wonder” vagrant birds, these trees rarely hold birds for long. On the other hand, even a single Coast Live Oak or sycamore, let alone a small grove, can hold vagrant birds for months. For a prime example of this, Black-and-white Warblers have been returning to the West San Gabriel River Nature Parkway near Long Beach for several years now, and each year, they reliably return to a small number of California Sycamore trees, staying for months at a time.
Magnolia Warbler on a Coast Live Oak at Bette Davis Park, Glendale, CA
Why is this the case? Quite simply, it’s because California natives are where the food is. Despite flying from across the continent, birds native and vagrant are largely after the same food items – insects – and because native insects co-evolved with native plants rather than exotic ornamentals, insect densities are much higher on these native plants.
If you live in Southern California, there’s a fair chance your yard will be visited by a vagrant bird sometime in the near future. If it is, the best way to make it feel at home – and motivate it to stick longer -- is not by enticing it with ornamentals it would recognize from its home range, but rather by planting California natives, which will offer the additional benefit of supporting our native birds, butterflies, and other wildlife.
